Chapter 5 part Deux (pages 167 - 216)
Wood-Destroying Insects and Fungi
|Table of Contents||Decay Fungi Species|
|Powderpost Beetles||False Powderpost Beetles|
|Deathwatch Beetles||Roundheaded Borers|
|Flatheaded Borers||Bark Beetles|
|Carpenter Ants||Carpenter Bees|
Table of Contents
Decay Fungi Species
- Molds and Stains
- Control of Decay Fungi
- Powderpost Beetles (Lyctidae)
- False Powderpost Beetles
- Deathwatch Beetles (Anobiidae)
- Deathwatch Beetle Species List
- Other Anobiids
- The Eastern Deathwatch Beetle, Hemicoelus carinatus (Say) (=Hadrobregmus)
- The Cailifornia Deathwatch Beetle, Hemicoelus gibbicollis (LeConte) (=Hadrobregmus)
- Ernobius mollis (L.)
- Priobium sericeum (Say) (= Trypopitys)
- Ptilinus ruficornis Say
- Xyletinus peltatus (Harris)
- ROUNDHEADED BORERS (Cerambycidae)
- FLATHEADED BORERS (Buprestidae)
- BARK BEETLES (Scolytidae)
- Bark Beetle Species List
The Genus Dendroctonus
- Western Pine Peetle, Dendroctonus brevicomis LeConte
- Mountain Pine Beetle, Dendroctonus ponderosae Hopkins
- Southern Pine Beetle, Dendroctonus frontalis Zimmerman
The Genus Ips
- California Fivespined Ips, Ips confusus (LeConte)
- Ambrosia Species List
- Scolytid Ambrosia Beetles
- Platypodid Ambrosia Beetles
- Wilson's Wideheaded Ambrosia Beetle, Platypus wilsoni (Swaine)
- WOODWASPS (Siricidae)
- Woodwasp Species List
- California Species of Woodwasps
- Woodwasp Damage
- Control of Woodwasps
- Carpenter Ant Species List
- Some California Carpenter Ants
- Camponotus nearcticus Emery
- Camponotus hyatti Henry
- Camponotus clarithorax Emery
- Camponotus vicinus Mayr
- Camponotus semitestaceus Emery
- Camponotus laevigatus (F. Smith)
- Camponotus modoc Wheeler
- Some Eastern Species
- Some California Carpenter Ants
- Control of Carpenter Ants
- Carpenter Bee Species List
- California Species of Xylocopa
- Mountain Carpenter Bee, Xylocopa tabaniformis orpifex Smith
- Valley Carpenter Bee, Xylocopa brasilianorum varipuncta Patton
- California Carpenter Bee, Xylocopa californica californica Cresson
- California Species of Xylocopa
- Economic Importance
- Control of Carpenter Bees
Decay Fungi Species
- Dry Rot, Poria incrassata
- Other Decay Fungi
Decay fungi grow on and in wood, and destroy the wood substances as they grow. Generally, conditions that are favorable for subterranean termites are also favorable for decay fungi, and vice versa. Temperature affects the activity of both termites and decay fungi and thereby affects the rapidity of their destructive action. Subterranean termites and decay fungi both require an abundance of moisture, but termites can obtain their moisture in galleries situated in moist soil and can then feed on dry wood, whereas most decay fungi cannot colonize and decay wood which is below the fiber saturation point, a moisture content of about 30% (Amburgey, 1972). However, some fungi can transport their own water from damp soil.
Dry Rot, Poria incrassata
This is the most destructive fungus. It becomes established in wood on or under damp soil, such as in foundation forms left alongside a foundation or under a porch slab. It can transport its own water from the moist soil to normally dry wood. Both coniferous and broadleaf species of wood are attacked, but the fungus is generally confined to structural timbers in buildings or to stored lumber. Poles, posts, ties, or slash in the forest are rarely attacked. The fungus occurs throughout most of the United States, but particularly in the southern and Pacific Coast states (Humphrey, 1923; Boyce, 1961).
Description. Water is conducted from damp ground through strands of mycelium comprising the rhizomorph, which is rootlike in appearance (figure 102, bottom). The rhizomorph varies in color from white to brown to brownish black, depending on its age, and varies from 3 mm to as much as 5 or 8 cm in thickness. The water-conducting strands can extend for 30 ft (9 m) or more across the surface of concrete, brick, or other impenetrable material and upward to the second or third floor of a building, spreading out into flattened veins embedded in sheets of mycelium. Over this entire area, the wood is moistened by the fungus and made susceptible to decay, even though it would otherwise be too dry.
The wood is moist while the fungus is alive, and in a cross section of infested timber, progress of the fungus is indicated by a dark stain (figure 102, top). The common name, "dry rot," presumably derives from the appearance of the wood after the fungus is dead. The severely decayed wood is brown, and breaks up into irregular chunks resulting from shrinkage cracks both across and in the direction of the wood fiber (figure 102, bottom). Sheets of white mycelium can often be seen in the cracks. Owing to the extraction of cellulose by the fungal hyphae, the wood becomes very light in weight and loses its structural strength. The dry material has a distinct odor where the more succulent fruiting bodies occur, reminding one investigator of "drying slippery-elm bark" or of certain of the fleshy Hydnums (fungi) when they are dried out (Humphrey, 1923). The fruiting bodies can reactivate the infection if the wood becomes damp again.
Paperlike, fanshaped sheets of mycelium that appear on wood in damp places are often the first indications of decay. Masses of mycelium may protrude along the bottoms of baseboards or where timbers are joined. Leathery, crustlike sporophores are produced annually. They vary in color, from orange through olivaceous to deep purplish black, depending on their age and location, and all these colors may be represented in order from the margin to the center of a single fructification (Boyce, 1961).
Type of Wood Attacked and Rate of Destruction
It happens that the rough frame lumber most commonly attacked by dry-rot fungus is coniferous, but Humphrey (1923) pointed out that the fungus is an omnivorous saprophyte that can attack and destroy almost any of the commercial woods of the United States, even such reputedly highly durable ones as cedar, cypress, juniper, sequoia (redwood), catalpa, greenheart, black locust, sassafras, white oak, black walnut, and black cherry, all of which are severely attacked and sometimes completely destroyed.
Rapidity of Destruction
Another important characteristic of Poria incrassata is the rapidity with which it can destroy structures. A frame house in Florida suffered severe loss in 3 years, and in 5 years about 25% of the house was visibly affected. A 3-year-old house in Kentucky suffered severely from decay of subfloor timbers, flooring, and casings. In another house in Louisiana, much of the front wall and 750 sq ft (69 sq m) of flooring had to be replaced within 3 years after construction. In a store in that state, heart cypress paneling laid over a brick wall lasted only 6 months (Humphrey, 1923).
The same kind of decay as produced by Poria incrassata is produced by the teardrop fungus, Merulius lacrymans, which occasionally causes much damage to structural timbers in the northern part of the United States and in Canada. The 2 rots cannot be distinguished unless sporophores are present. In Europe, where P. incrassata does not occur, M. lacrymans is the "dry-rot fungus," and is very important.
A considerable amount of what has been said about P. incrassata pertains also to M. lacrymans, including the rhizomorph and its water-conducting capacity. The specific name lacrymans, which means "weeping," refers to the characteristic the fungus shows in active growth under damp conditions, when innumerable globules of water are seen, "which sparkle in the light of a torch like a large number of teardrops" (Hickin 1963c).
The mycelium of the teardrop fungus grows rapidly, and is snowy white, but where the edge of an expanse of mycelium comes into contact with drier air or is exposed to light, it becomes bright yellow (Hickin, 1963c). When the mycelium of the closely related Poria incrassata grows through the cracks in the floor into a lighted room, the mycelium turns orange in color, and this color change has been likewise observed in partially lighted basements (Humphrey, 1923)
The prodigality of nature is indicated by the estimate that 1 sq m of a sporophore of M. lacrymans will produce over 50 million spores per minute over a period of many days, and that other wood-decay fungi have been found to be even more fruitful.
Many species of decay fungi attack buildings. In New York state, Poria incrassata is not known to occur, but in an extensive survey, 11 other species of Poria were found attacking wooded buildings, resulting in 22.8% of the incidence of decay. In the same family of fungi (Polyporaceae) Lenzites saepiaria made up 12.4% of the total and, in the family Hydnaceae, Odontia spathulata was found with about the same frequency (12.8%,) (Silverborg, 1953). The latter species produces a white, stringy rot, unlike the brown, cubical type associated with the other common building-decay fungi. In the foregoing investigation, Lenzites trabea was found in 4.6% of the instances of decay. This fungus came prominently to the attention of entomologists in the early 1960's, when an extract from L. trabea rotted wood was found to be an attractant to termites (Esenther et al., 1961). It was later discovered that this extract induced trail-following by the eastern subterranean termite, Reticulitermes flavipes, similar to that induced by a trail-marking pheromone secreted by the sternal gland of this insect (Smythe and Coppel, 1966a). Trail-marking substances isolated and purified from R. viriginicus and from wood infested with L. trabea were found to be identical (Matsumura et al., 1969).
Wood may be attacked by molds, which are superficial fungi, generally green, yellowish green, red, or black, depending on the species. Molds do not damage wood and can be easily scraped off, but they indicate that conditions are right for the growth of decay-producing fungi and that corrective measures should be taken.
Wood is also affected by sap-stain or blue-stain fungi. They penetrate more deeply than molds, but do not significantly weaken the wood. The fungi are usually bluish, and cannot be scraped off wood like molds. They do no damage unless they occur where they may be considered to be unsightly, but like the molds, they indicate that conditions are favorable for the growth of the more destructive decay fungi (Anonymous, 1963).
Control of Decay Fungi
The same measures and precautions during and after construction that decrease the susceptibility of subarea structural timbers to subterranean termites also pertain to the control of decay fungi. They include not only the measures practiced to eliminate excessive moisture, but also the use of pressure-treated lumber and the removal of all wood scraps or other cellulose debris that might provide food for fungi or termites.
All that is required for the control of a waterconducting decay fungus such as Poria incrassata is to break the connection between the source of water and the infected structural wood member. The source of water should be eliminated, if possible, and the water-conducting rhizomorphs should be removed. The wood will then dry out and the fungus will die. Replacement of the infected wood member is required only if the wood is too weak to support its load. Verrall (1968) advised against dependence on surface applications of wood preservatives, or on such supposedly decay-resistant woods as redwood, as controls against fungi that are "water-conductors."
Wood used in construction should not have a moisture content of more than 20%. Depending on the atmospheric conditions in the area in which it is dried, air-dried wood may have a moisture content between 6 and 24%, whereas kiln-dried wood has a content of from 6 to 12% Wood that is not pressure-treated with a wood preservative should not be allowed to contact the soil. The caulking around windows, doors, bathtubs, and sinks should be maintained to prevent accumulation of water in walls. Paint decreases penetration of water into wood except at joints between the wood members (Amburgey, 1972).
In many homes, condensation of moisture within insulated walls and floors favors wood decay. Warm, moist air passing into walls comes in contact with wood members with temperatures below the dew point of the air, resulting in deposit of excess water. Measures that may be taken to reduce or prevent condensation vary in different geographical regions, and are discussed in chapter 10, under "Sources of Moisture in Buildings."
POWDERPOST BEETLES, FALSE POWDERPOST BEETLES, AND DEATHWATCH BEETLES
- Powderpost Beetles (Lyctidae)
- False Powderpost Beetles (Bostrichidae)
- Deathwatch Beetles (Anobiidae)
The insects discussed in the preceding part of this chapter do not make their presence known by exit or entrance holes at the surface of infested wood. One must usually break into the wood and uncover their galleries in order to locate the infested areas. The insects discussed in the following pages make their presence known by exit holes, sometimes so numerous that the surface of the wood looks as if it had been riddled by a charge of birdshot. The most important group of insects that attack wood in this way includes 3 closely related families of beetles (Lyctidae, Bostrichidae, and Anobiidae), the larvae of which reduce wood to a mass of powdery or pelleted frass. They attack dead wood almost exclusively, especially dried and cured lumber, and several generations can reinfest the same piece of wood until only the outer shell remains, riddled with exit holes. Beneath the surface of the infested wood are frass-filled galleries or tunnels, usually coursing along the grain of the wood.
The damage caused by these 3 families of beetles can be identified as follows: The true powderpost beetles (Lyctidae) loosely fill their galleries with very fine powder, similar in appearance to face powder; the false powderpost beetles (Bostrichidae) tightly pack their galleries with a coarser boring dust, often containing small wood fragments; and the deathwatch beetles (Anobiidae) fill their galleries with small pellets. The frass in the galleries of the bostrichids and anobiids is not only coarser than that of the lyctids, but tends to stick together. Although all these beetles have sometimes been collectively referred to as "powderpost beetles," in a more definitive sense the term should apply only to the lyctids, for their larvae are the only ones that produce a fine, powderlike dust in their galleries.
The homeowner often asks whether the damage he sees lias been caused by termites or beetles. Damage to wood caused by lyctids, bostrichids, and anobiids is likely to be first noticed when the round emergence holes of the adults are seen or the beetles are found on infested wood, such as windowsills.
Probing or tapping the infested area of the wood will usually reveal one of the types of frass described above. In the United States, the fine powder of the lyctid beetles is most often encountered. In the wood structure of the building, beetle infestations occur most often in hardwood cabinets and flooring. On the other hand, the presence of subterranean termites usually first comes to the attention of the homeowner when he sees blisters or dark stains in flooring or other wood or where the paper-thin surface covering the infested wood is crushed, as when furniture is moved about.
When the structural damage is caused by termites, there are no exit holes in the vicinity, and their irregular tunnels are not filled with powder. Drywood termite tunnels may hold many pellets, but the pellets are larger than those produced by deathwatch beetles (anobiids), are characteristically sculptured, and are blunt at each end (figure 83, this chapter). The presence of drywood termites usually comes to the attention of the occupants of a building when the pellets are pushed out of occasional "kickout" holes in wood members, such as the frames of doors or windows or exposed timbers.
There can be no confusion between the typical appearance of termite workers and the worm-like larvae of beetles. The winged reproductives of termites are often seen during their brief, fluttering flights. After they have landed and are crawling about, they are often mistaken for "winged ants."
On the other hand, all of the adult lyctid and anobiid beetles are strong fliers and are attracted to light. They may, therefore, often be discovered at or near windows when an infestation occurs in a room. Even experienced ento- mologists often mistake the furniture beetle, Anobium punctatum, for a fly, since in flight .it closely resembles the latter, even to the extent of flying around light bulbs (Hickin, 1963a).
Powderpost Beetles (Lyctidae)
Powderpost Species List
- Southern Lyctus Beetle, Lyctus planicollis LeConte
- Western Lyctus Beetle, Lyctus cavicollis LeConte
- Brown Lyctus Beetle, Lyctus brunneus (Stephens)
- European Lyctus Beetle, Lyctus linearis (Goeze)
- Velvety Powderpost Beetle, Trogoxylon parallelopipedum (Melsheimer)
- Minthea rugicollis (Walker)
- Lyctoxylon japonum Reitter
Lyctids are small beetles ranging from 2 to 7.5 mm in length. They are reddish, various shades of brown, or black; have a prominent head not covered by the prothorax; short, 11-segmented antennae, each with a 2-segmented terminal club and tibiae with distinct spurs (figure 103).
To distinguish between species of Lyctidae, a description of certain features of the elytra is generally utilized. The interspace (figure 103) is the surface between striae; a stria is a longitudinally depressed line or furrow, frequently punctured, extending from the base to the apex of the elytra; and a carinula (diminutive of carina) is a keel-like ridge.
Lyctids are cosmopolitan, each geographical region having indigenous as well as established introduced species. Of the 66 known species, 10 occur in the continental United States and 6 of these are common and important as pests. In the United States, species of Lyctus and Trogoxylon are widely distributed. Species of Minthea and Lyctoxylon are often intercepted in wood products in maritime ports of entry. Representative species of these 4 genera are shown in figure 104. In this country, lyctids are second only to termites in their destructiveness to wood and wood products, but confine their attacks to large-pored hardwoods such as oak, ash, hickory, mahogany, and bamboo. Powderpost beetles may be found in hardwood flooring, hardwood timbers, plywood, and wood articles such as crating, furniture, antiques, tool handles, spokes of wheels, gunstocks, etc., causing millions of dollars' worth of damage every year
The damage the beetles cause consists of reducing sound wood to fine powder, and is usually not evident until the emergence holes of the adults are seen (Gerberg, 1957b).
Lyctids are generally brought into buildings in wood that contains their eggs or larvae. Lumber should be examined for signs of infestation. Once in a home, hardwood items are usually finished with paint, varnish, shellac, sealer, or wax, which treatments prevent oviposition by adult beetles.
If the adults' emergence holes are found in such finished items, it may usually be assumed that the infestation began before the finish was applied. From an economic standpoint, the 2 most important lyctid species in the United States are Lyctus planicollis and Trogoxylon parallelopipedum.
Southern Lyctus Beetle, Lyctus planicollis LeConte
This is a predominantly Nearctic species (plate II, 1; figures 104, 105, 106), found throughout the United States and in parts of Mexico. It is about 5 mm long, and is black when fully chitinized. The males are much smaller than the females. The prothorax usually has a broad, shallow, median depression. The interspace is composed of 2 regular series of elongate punctations, and the striae are separated by rows of fine, long hairs. The tenth antennal segment of L. planicollis is wider than long, whereas in the closely related L. cavicollis it is not wider (Gerberg, 1957a).
Western Lyctus Beetle, Lyctus cavicollis LeConte
This species is widespread throughout the United States. It varies from 2.5 to 5 mm, but usually is not over 3 mm in length. It is slender, and rusty brown. The anterior portion of the prothorax is narrower than the combined bases of the elytra. As in L. planicollis, the striae punctures are in a double row. In California, L. cavicollis mines the seasoned wood of eucalyptus, hickory, oak, and orange, and is also destructive to any products made of these woods. It often infests oak firewood, and can spread to hardwood flooring, paneling, and furniture.
Brown Lyctus Beetle, Lyctus brunneus (Stephens)
This is a cosmopolitan species that may have been originally Neotropical, but has shown the ability to adapt itself readily to other zoogeographcal regions. Its length can be 2.2 to 7 mm, but is usually 4 to 5 mm. It is slender, brown, with black head and prothorax. The interspaces of the elytra have a single row of punctations, and not all interspaces are separated by longitudinal carinulae.
European Lyctus Beetle, Lyctus linearis (Goeze)
This is another cosmopolitan species that resembles L. cavicollis in size and color, but can be distinguished by having single rather than double rows of punctations of the elytral striae, and by its prominent frontal lobes. It is commonly found in commercial products of ash, wild cherry, hickory, oak, locust, poplar, and walnut, and in California it has been reared from dead grape canes and limbs of oak, orange, and sycamore (planetree) (Essig, 1926). It is common in the eastern United States, but not so much so in the western states (Linsley, 1943b).
Velvety Powderpost Beetle, Trogoxylon parallelopipedum (Melsheimer)
The velvety powderpost beetle (figure 104, B) is Nearctic, occurring throughout the United States. It is 2.5 to 4.3 mm long, and rusty red- brown to black. The elytra are about twice as long as wide, and have a fine, golden pubescence. It attacks seasoned hardwoods, but has also been found boring into the trunks of living honey-locust (Gleditsia triacanthos) in Indiana (Gerbera, 1957a).
Minthea rugicollis (Walker)
The genus Minthea is characterized by the erect, flattened hairs along the denticulate lateral margins of the pronotum (figure 104, C). The elytra have 6 or 7 rows of erect, flattened, whitish hairs, usually separated by a row of fine, reclining hairs. The adults are 2 to 3 mm long. The terminal segments of the antennae are slightly longer than the preceding ones, and the lateral margins of the pronotum bear about 19 flattened hairs. This species is found throughout tropical regions. It has been intercepted in quarantine in the United States in wooden articles, and even in such products as ivory nuts (Phytelephas macrocarpa; Palmaceae) and dried roots of Derris elliptica (Legtiminosae) (Gerberg, 1957a, b).
Lyctoxylon japonum Reitter
This genus can be readily distinguished by the elongate antennal club: both segments are longer than broad, and the terminal segment is narrower than the preceding one (figure 104, D). The beetles are 1.5 to 2 mm long. The species is apparently distributed throughout the Orient, but may have become established in Panama. It is often intercepted in quarantine in the United States, usually in bamboo (Gerberg, 1957a).
The Life Cycle of Lyctid Beetles
Adult lyctids mate soon after they emerge from infested wood. Oviposition begins 2 or 3 days later, and continues for a week or two, most of the eggs being laid within the first 7 or 8 days. The female has a long, flexible ovipositor that she inserts deeply into the pores of hardwoods, laying 1 or several eggs in each pore. Investigators generally report that the female places her eggs only in the spring in wood vessels or pores. These are exposed when the wood is cut, or may be opened by the beetle herself. Cymorek (1965) observed that Lyctus brunneus and Lyctus africanus Lesne did not restrict their oviposition to the vessels of the wood, but also oviposited in all kinds of cracks and crevices. He also found that both species could oviposit and develop in corn and wheat grains in the laboratory.
From 15 to 20 eggs per female have been reported for L. linearis and 17 to 21 for L. brunneus. The lyctid egg is about 1 mm long, translucent white, and cylindrical, with rounded ends, and bears a threadlike process at the anterior end (figure 107). Eggs are never deposited in polished, waxed, varnished, or painted surfaces (Gerberg, 1957a).
The incubation period can range from 1 to 3 weeks, depending on temperature. The emerging larva is white, straight-bodied, and bears a pair of small spines at the rear. After the first molt, the larva assumes a curved form. The young larva usually tunnels with the grain of the wood, but later takes an irregular course, sometimes intersecting its earlier track or the tunnels of other larvae. The tunnels are packed with a fine, powderlike dust. The larvae do not penetrate to the surface but, like termites, leave a thin, unbroken surface layer. Outdoors, the larvae grow chiefly during spring and summer, but in heated rooms they can develop continuously.
A mature larva is usually less than 5 mm long, curved, and enlarged at the thorax. Its antennae are 3-segmented and have an accessory appendage. The abdomen bears 8 spiracles, and the most posterior pair is 6 times larger than the others (figure 108). The legs are distinct, 3-segmentcd, and unclawed. In contrast to lyctid larvae, the larvae of anobiids do not have an enlarged posterior spiracle and they have 5-segmented legs, with the terminal segment clawed (figure 108). The mature lyctid larva bores to a point near the surface of the wood and builds a pupal chamber (figure 105). The pupal period lasts from 12 days to a month. After metamorphosis, the adult chews its way to the surface, forms an exit hole 2 or 3 mm in diameter, and generally pushes some of the fine dust out of the hole when emerging (figure 109). Small piles of the dust are common near new emergence holes. Although the larva confines its burrowing to sapwood, if the adult has no other way of emerging, it can bore its way through heartwood, softwood, asbestos, lead sheeting, or plaster (Tooke, 1949).
Adult lyctids conceal themselves in cracks and holes in the wood during the day, but they become active at night, fly readily, and are positively phototactic (Gerberg, 1957b). Indoors, they may be seen crawling on floors, windowsills, furniture, and other surfaces.
The life cycle, from egg-laying to emergence of adults, ordinarily requires 9 to 12 months, but under exceptionally favorable conditions of high temperature and high starch content of wood, that period may be reduced to only 6 or 7 months. Two generations a year are not uncommon in the southern United States, but under adverse conditions of temperature and nutrients, the life cycle may be prolonged to 2.5 to 4 years, or longer (Gerbera, 1957a, b). Development of Lyctus brunneus was greatly prolonged in compressed oak sapwood when compared with the same wood before compression (Cymorek, 1967). There can be a great difference in the length of the life cycle of different species; the average for Trogoxylon parallelopipedum, for example, being 3 to 4 months compared with 9 to 12 months for Lyctus planicollis (Gerbera, 1957a).
Wright (1960) investigated the life cycle of L. planicollis in a laboratory under uniformly high temperature (31 °± 3 °C av. 88 °F) and at 85 ± 5% relative humidity. He reared the beetles on red-oak wood chips or wood flour. The mean incubation period for eggs was 8.2 days. The mean length of the larval stage was not determined, but some larvae remained alive as long as 42 days. A prepupal stage, not recorded earlier, lasted from 2 to 5 days. The mean pupal period was 8.1 days. The mean length of adult males was 3.5 mm and of adult females, 3.7 mm. The 2 sexes occurred in approximately equal numbers. The mean adult life of males was 33.1 days and of females, 35.1 days. Adult beetles lived about 2 weeks after emergance from the wood. The number of eggs deposited per female ranged from 18 to 122, with a mean of 51.4.
Factors Affecting Lyctid Infestation
Starch Content of Wood. Lyctid beetles primarily infest the sapwood of hardwoods. Ash, hickory, maple, and oak are preferred, but many other hardwoods are sometimes damaged. Bamboo, which is a grass, not a hardwood, is readily attacked in the Orient, frequently by Lyctus brunneus. Their chief source of food is starch, and whatever sugar and protein may be present; they do not digest cell walls, for the larvae cannot digest cellulose, hemicellulose, lignin, or pentosans - these pass through the intestine undigested. Lyctids will not oviposit in sapwood with a starch content of less than 30% and the greater the concentration of starch, the better they thrive.
The starch content of lumber depends on the tree species, the season the tree is cut, and the method by which the lumber is dried. Lyctids prefer recently dried rather than old wood because the starch content of lumber decreases as it is converted to lignin in the long process of natural seasoning.
Water Content of Wood. A definite range of water content is also necessary. Lyctids can live in wood with a water content of between 8 and 32%. Since the water content of green wood is commonly about 50% and can be even higher, it is obvious why attack by powderpost beetles is generally confined to partially or wholly seasoned wood (Christian, 1940a, b; 1941; Tooke, 1949). The moisture content of seasoned wood in the United States is said to average between 12 and 15%. The greatest lyctid beetle activity is found in wood with a moisture content of from 10 to 20% (NPCA, 1961).
Pore Diameter in Wood. The diameters of the pores or vessels in the wood can be a limiting factor, for they must be large enough to allow insertion of the ovipositor, otherwise oviposition cannot take place. The average size of the ovipositor of Lyctus brunneus is 0.078 mm; of L. linearis, 0.083 mm; and of L. planicollis, 0.076 mm (Parkin, 1934). Hardwoods with pores or vessels with diameters greater than these dimensions are subject to infestation. Softwoods or conifers do not have pores, usually have a low starch content, and generally are immune to infestation.
Natural Enemies. Natural enemies of lyctus beetles are common in infested lumber in millyards (Snyder, 1926; Christian, 1941). Among 6 species taken from an infested piece of wood, Christian found 2 predaceous clerids, Tarsostenzis univittatus (Rossi) and Monophylla terminata (Say), as well as 4 parasitic Hymenoptera, Monolexis fuscicornis Foerster [=M. lycti (Cresson)], Sclerodermus macrogaster Ashmead, Heterospilus n. sp., and Ecphylus n. sp.
False Powderpost Beetles (Bostrichidae)
False Powderpost Species
- Black Polycaon, Polycaon stoutii (LeConte)
- Leadcable Borer, Scobicia declivis (LeConte)
- Other Bostrichids
The bostrichids are small to large beetles, usually elongate and cylindrical, and are brown, reddish brown, or black. Unlike the lyctids, in most bostrichid species the head is deflexed and not visible from above, being hidden from view beneath a large thorax that gives the beetle a humpbacked appearance. The thorax is noticeably roughened in most species. The antennae are short in both families, but the bostrichids have 3 or 4 enlarged, sawtoothed, terminal segments, compared with 2 for the lyctids. The first abdominal segment of bostrichids is equal in length to each of the others, whereas in the lyctids it is longer than the others (figure 103). The tibiae have distinct spurs.
The Lyctidae and Anobiidae do not contain large-sized species, whereas the bostrichids have a considerable number of them. The most striking example is the palm borer, Dinapate wrightlii Horn, that is 4 to 5.5 cm long and infests native fan palms in California deserts and Baja California.
The bostrichids differ from the other 2 families mentioned in that the adults bore into the wood, preparing "egg tunnels" instead of ovipositing in surface cracks or pores. The female oviposits in pores leading from the tunnels. The larvae also bore tunnels. Thus, the bostrichids' tunnels vary greatly in size and shape. Like the lyctids, bostrichids can continue to breed in a piece of wood as long as it affords adequate sustenance. However, some species attack and breed in both hardwoods and softwoods.
The bostrichids are most abundant in the tropics, and are not so important as the lyctids and anobiids in temperate regions. Several species mine dead, seasoned, or cured hardwoods or hardwood furniture. Some species of Amphicerus and Polycaon burrow into the small twigs of living fruit trees, usually at the crotch or bud axil, but are usually not abundant enough to cause serious damage.
Black Polycaon, Polycaon stoutii (LeConte)
This is a cylindrical, coal-black beetle, 11 to 22 mm long and rather atypical of the bostrichids (figure 110). Unlike most of this family, the head is prominent and exserted. The pronotum is oval, not hoodlike, and has no tubercles. The punctures on the head and pronotum are coarse, and on the elytra they are fine. This species occurs in the Pacific Coast states and in Arizona, where it is the largest member of the genus. It attacks almost any of the softwoods and several of the hardwoods. As a pest, it is most common in 3-ply panel used for making desks and similar articles. The beetles fly at night, and can attack stacked plywood. The larvae burrow in the inner portion of the panel in a softwood such as basswood, where they require 1 or more years to complete their development. Their presence is not discovered until the adults emerge, burrowing through the outer layers of hardwood such as oak or mahogany, leaving emergence holes about 7 mm in diameter. The beetle does not infest finished products after manufacture, and its emergence holes will indicate that a portion of the wood was infested before manufacture (Doane et al., 1936; Linsley, 1943b).
Although Polycaon stoutii is generally reported in the literature as occurring in furniture, particularly veneer furniture, Mallis (1969) stated that it would also attack cured hardwoods in the lumberyard and buildings in mountainous areas. Pest control operators have captured and obtained identification of adults emerging from hardwood flooring over a subfloor of Douglas fir, the beetles having originated in the fir.
Leadcable Borer, Scobicia declivis (LeConte)
Leadcable borers are common along the Pacific Coast, particularly in California and southern Oregon, occurring at all elevations up to 5,300 ft (1,600 m). Outdoors, they normally infest dead and seasoned oak (figure 111), but they will also infest acacia, eucalyptus, maple, California laurel, elm, chestnut, and other hardwoods. They can reinfest the wood from which they emerge. They occasionally attack newly painted houses, apparently being attracted to them, and have been known to infest hardwood paneling and floors. They are attracted to corks in bottles containing alcoholic beverages, or to hard liquors or wine in oak casks, and can damage the casks severely.
Description. The leadcable borer (figures 111, 112) is 5 to 6 mm long, cylindrical, brown or reddish brown to black (usually black), with reddish mouthparts, legs, and antennae. The antennae are 8-segmented, with the 3 terminal segments much enlarged, and most of the head is concealed from above by the hoodlike pronotum, as is generally the case with the bostrichids. The prothorax has many tubercles on the anterior half, and the elytra have deep, linear punctures.
Life Cycle. The life cycle of the leadcable borer was investigated in great detail by Burke et al. (1922). The female bores an egg gallery, beginning at any place where leverage can be obtained, such as a knot, scar, bark scale, crevice, or between 2 pieces of wood. After the gallery reaches a depth of some 8 mm, it turns abruptly and runs parallel to the surface and across the grain of the wood for approximately 6 cm. Mating usually takes place when the tunnel has reached about the length of the female. The eggs are deposited in pores at a distance of 1 to 2.5 mm from the gallery - a single egg in each pore. The female apparently stops at any suitable pore to oviposit as she goes back and forth to throw out the borings. Some eggs are found so close to the gallery entrance that it appears the female can also back down into the gallery to oviposit.
The dull-white or cream-colored egg is very elongate, averaging 2.1 mm in length, including the stem, and 0.14 mm in width. It hatches in about 3 weeks. The larva mines parallel with the grain of the wood, packing its borings behind it, and becoming full grown (figure 112) after 6 molts and in a period of about 9 months. By the time it is ready to pupate, it has mined out a gallery 50 to 60 cm long. No distinct pupal cell is made. The prepupal larval skin gradually becomes transparent, and the pupa (figure 111) can be seen within for about 6 days before the skin is shed. The pupal stage lasts about 14 days, and the adult remains in the wood for a month to 6 weeks, hardening and maturing and becoming darker brown and finally black. The adult then eats its way out of the outer wood and bark. After emerging, the males live from 10 to 18 days and the females 30 to 44 days, provided they have access to wood; otherwise, both sexes die in 5 to 7 days. There is 1 generation a year. Adult beetles may be seen from the middle of April to the last of September, but they are most common in July and August.
Types of Damage. The usual damage to wood is a complete riddling caused by the egg galleries of the adults and the larval tunnels packed with a meal-like frass, leaving nothing but the bark and enough solid wood to hold the tunnels together (Burke et al., 1922).
The leadcable borer derived its name from its ability to bore through the lead sheathing of aerial telephone cables, making holes 2.5 mm wide. Much damage and great losses occur when moisture enters the cables, causing short circuits. According to Linsley (1943b), the adults appear to be greatly stimulated by heat, and sometimes bore into lead or asphalt roofing materials because of high temperatures. Such attacks, as well as attacks on lead cables, can be precipitated by forest fires, particularly in oak, where the beetles may occur in large numbers.
Various species of beetles that bore into lead and other metals include other bostrichids, as well as certain anobiids, lyctids, ptinids, buprestids, cerambycids, anthribids, bruchids, curculionids, dermestids, and tenebrionids. Insects of other orders that can do the same are termites; woodwasps (Siricidae); certain carpenter moths (Cossidae) (Burke et al., 1922; Chamberlin, 1949); and some species of carpenter bees (Xylocopa) (H. Scott, 1932; Middlekauff, 1960).
In May and June, 1972, many houses in 2 new residential tracts in Fresno, California, were infested with leadcable borers. Adult beetles emerged from the acoustic layers of the ceilings and from the wall plaster - as many as 50 beetles in 1 house - leaving holes about 2 mm in diameter. The probable sources of the beetles were piles of heavily infested fig prunings in an orchard situated between the 2 tracts. Scobicia declivis was reared from portions of dried fig branches taken from these piles. Also reared was another bostrichid, Amphicerus cornutus (Pallas), siniilar to S. declivis in superficial appearance but much larger (11 to 13 mm long). The leadcable borer had not been recorded before from the fig. The beetles probably entered the attics via the attic vents or by crawling beneath shingles. With none of their favored wood species to attack, they tried to escape from the attics by crawling down through holes made in the ceiling plates for electrical conduits. The conduits were in the corners of the rooms, and the beetles' emergence holes in the plaster were likewise always found in these corners. The infestations ceased after the piles of fig prunings were burned (Ebeling and Reierson, 1973b).
Probably the most common bostrichid in the eastern United States is the redshouldered shothole borer, Xylobiops basilaris (Say), which can attack practically any freshly cut and partially seasoned hardwood, and has been found attacking partially seasoned pecan lumber. It principally attacks the wood of hickory and persimmon, although it has been found in elm and other species. It has been found in lumber shipped to England (Craighead, 1950). St. George (1970) considers X. basilarus to be the only powderpost beetle in the eastern states that seriously damages wood products such as log cabins, rustic bridges, or wood used in the manufacture of rustic furniture, rustic fences, arbors, and wooden tool handles. Sometimes this beetle causes a 50% loss in these wood products. In the usual manner of bostrichid beetles, the adult bores in from the outside and down through the bark of freshly cut wood. It mines a tunnel in the wood for a short distance, following the annual rings, and this serves as an egg tunnel. Most of the larval boring is in the sapwood, which is ultimately destroyed (Chamberlin, 1949; St. George, 1970).
In the Midwest, Scobicia bidentata (Horn) is commonly found in the freshly cut wood and lumber of many hardwood species.
The bamboo borer, Dinoderus minutus (F.) (figure 113), is a cylindrical brown beetle, 3 to 4 mm long, which is indigenous to Asia but is now cosmopolitan in distribution. It attacks bamboo furniture, poles, and ornaments, as well as drugs, spices, stored grain, and flour. Powder sifting from cracks in bamboo and adult beetles found in buildings after emerging from bamboo articles are usually the first indications of infestation. It is particularly destructive in the West Indies (Plank, 1948).
Heterobostrychus aequalis (Waterhouse) is occasionally found in wood products imported from the Orient. The specimen shown in figure 114 was taken from imported mahogany furniture. This appears to be the most common of the larger bostrichids in India and parts of southeast Asia, where it bores into packing cases, boxes, plywood, furniture, and lumber, reducing the wood to a powder to a depth of 2 or 3 in. (5 or 7.5 cm) in severe infestations. In January, 1967, H. aequalis was found in oak lumber in Fort Lauderdale, Florida, and infestations were later found in Florida in lumberyards in the Fort Lauderdale and Miami areas and in an oak hammock near Hallandale (Woodruff, 1967). The species is now believed to be well established in Florida in scattered and localized areas (R. E. Woodruff, correspondence).
Heterobostrychus aequalis is 6 to 13 mm long, and reddish brown to brownish black. The anterior half of the strongly convex pronotum has broad, toothlike, marginal projections. The elytra are nearly tubular in shape back to the somewhat excavated apical declivity, which in the males has 2 incurved, hooklike projections. The surface of the elytra has deep punctures arranged in fairly distinct rows (Woodruff, 1967).
Deathwatch Beetles (Anobiidae)
Deathwatch Beetle Species List
- Furniture Beetle, Anobium punctatum (De Geer)
- Deathwatch Beetle, Xestobium rufovillosum (De Geer)
- Other Anobiids
- The eastern deathwatch beetle, Hemicoelus carinatus (Say) (=Hadrobregmus)
- The Cailifornia deathwatch beetle, Hemicoelus gibbicollis (LeConte) (=Hadrobregmus)
- Ernobius mollis (L.)
- Priobium sericeum (Say) (= Trypopitys)
- Ptilinus ruficornis Say
- Xyletinus peltatus (Harris)
There are about 260 species of anobiids in the United States, the majority of which feed on dead wood. However, 2 species, the cigarette beetle (Lasioderma serricorne) and the drugstore beetle (Stegobium paniceum) are important pests of stored food products. Anobiids are widely distributed, and in some parts of the world, for example in Europe and New Zealand, they are much more important than in the United States. They attack mostly sapwood, but can extend their attacks into heartwood, and they attack both hardwoods and softwoods.
Anobiids range from 1.1 to 8 mm in length, and are highly variable in body form, ranging from narrow and elongate to nearly circular from the dorsal aspect. When viewed from above, the hoodlike or "bellshaped" pronotum usually conceals the head, as in the case of the Bostrichidae and Ptinidae, but is unlike that of the true powder-post beetles (Lyctidae), in which the head is not hidden when viewed from above. The last 3 segments of the antennae are usually lengthened and broadened, or simply lengthened, but in some species the antennae are either serrate (sawtoothed) or pectinate (combshaped). (The antennal clubs of lyctus have only 2 segments.) The tibiae lack the spurs found on the tibiae of the lyctids and bostrichds. The tarsi are 5-segmented, with divaricate (widely separated) claws.
Illustrations of some of the anobiids that have been recorded as pests in the United States are shown in figure 115.
Furniture Beetle, Anobium punctatum (De Geer)
The potential for damage from the furniture beetle in the United States is indicated by the estimate made by Hickin (1963a) that at least 50% of the buildings of Great Britain contained an active infestation by this species, and possibly 20% of those built since World War II were infested. In that region, the furniture beetle is the principal species involved in "woodworm" damage - a large portion of the business of pest control operators. The beetle attacks structural timbers, paneling, flooring, and furniture In Germany, it is said to infest "nearly every building," and in New Zealand, it is believed to occur in every house that has been in existence more than 15 years. As the common name implies, the insect commonly infests furniture and other wooden articles.
In the United States, the furniture beetle is widely distributed, but has nowhere attained the importance it has in Europe. It is fairly common in the East, but not along the Pacific Coast, where infestations are usually isolated in imported furniture. The species is confined to the temperate regions of the world, and is not likely to become a pest in tropical regions except at high altitudes where the climate may be suitable for its development.
Even in temperate regions where it is well established, the incidence of infestation and the parts of a building infested can be greatly influenced by differences in climate within a small area. Thus, in Norway A. punctatum was found as frequently in attics as in cellars near the coast where summer temperatures were low, whereas relative frequency of infestation in attics decreased with increasing distance from the coast because of increasing summer temperatures, affecting attics more than cellars (Knudsen, 1967).
The furniture beetle attacks only well-seasoned lumber, provided the surface offers ovipositional sites, and it attacks wood only if the bark is removed. Exit holes of this species are never seen in the bark (Hickin, 1963a, b). Oviposition is greatly reduced on normally favored wood if it is finely sandpapered, painted, or varnished, all of which eliminate oviposition sites (Kelsey et al., 1945). According to Hickin (1949), it is rare for softwood to be attacked until about 20 years, and the sapwood of oak about 60 years, after it has been cut. However, exit holes have been found in birch plywood as little as 5 or 6 years after being cut.
Description. The furniture beetle (figure 115, A) is 4 to 6 mm long, cylindrical, reddish brown to dark brown, with longitudinal rows of pits on the elytra. These punctures are clearly visible through the fine, yellowish hairs that cover the beetle. As in all anobiids, the head is not visible from above; this distinguishes adult anobiids from the lyctids. The head has a prominent frontal protuberance, and the antennae are 11-segmented with the last 3 segments enlarged so that the 3 together are longer than the first 8 segments combined (White, 1962).
The grayish-white larva is about 6 mm long. Spinules occur on the first 7 abdominal segments, and are absent on the last 3 segments. On the first 6 segments, the bands (transverse markings) have 2 rows of spinules, and on the seventh segment the band has only a single row. A tubular projection or air tube on each spiracle is about equal to the length of the spiracle itself, and is longer than the projections on the spiracles of other common anobiid larvae. As stated earlier, anobiid larvae differ from lyctid larvae in not having a greatly enlarged posterior spiracle and in leaving 5-segmented legs, the terminal segment with a claw (figure 108). The tunnels formed by the larvae, mostly along with the grain of the wood, are loosely filled with frass. The frass consists of cigar- shaped pellets composed of minute fragments of the chewed wood. In severe infestations, large amounts of frass may be forced out of old exit holes, but "powdering" does not occur to the same extent as with lyctid beetles (Hickin, 1963a).
Life Cycle. Adults emerge in the spring from pupal cells just below the surface of the wood. They mate soon after emergence, and a day later the female lays her eggs in a crack or crevice in the wood (figure 116), in rough end-grain, rough-sawed timber, unplaned wood where the grain is open, or just inside old emergence holes (Hickin, 1963a, b). The eggs are easily seen with the unaided eye, appearing like groups of "oval pearls," but are often slightly deformed when forced into crevices during deposition (Hickin, 1963). The average number of eggs laid has been reported to be 18 by Kelsey et al. (1945), 28 by Hickin (1963a) and, in the laboratory, 54.8 by Spiller (1964). The eggs ordinarily hatch in 6 to 10 days. Spiller (1949) observed either no hatching or impaired hatching at relative humidities below 60%.
Outdoors, the larvae require about a year for development, and will pupate for 2 to 3 weeks in a cell just below the surface of the wood. Indoors, the life cycle may require 2 to 3 years or more; this may result in a staggering of generations, so that all stages may be found in the wood at any one time. The longer indoor developmental period is presumed to be the result of a lower moisture content of the wood (N. E. Hickin, correspondence)
Deathwatch Beetle, Xestobium rufovillosum (De Geer)
The deathwatch beetle is so named because of a mating signal produced by each sex by striking its head against the surface on which it stands. A female captured immediately after emergence was placed in a small box, where she continued to live for 10 weeks. During this period, she would respond in kind when a tapping noise was made with a pencil within a few meters of the box. This tapping was once considered to be a foreboding sound or death signal by superstitious people (Gahan and Laing, 1932). Deathwatch beetles seldom if ever fly, although they will sometimes flutter their wings when thrown into the air.
Wood must be partially predigested by fungi before the deathwatch beetle can utilize it. In nature, it attacks several hardwood species. Indoors, it infests hardwood timber that was at some time infected with fungi. In England, where so many buildings are constructed of oak, this is the principal timber infested. The timbers most likely to be attacked are those soaked by rain or that are in poorly ventilated locations. Infestation always originates in hardwood, but can extend into adjacent softwood. Heavy furniture is often infested, particularly if made of oak or chestnut. Deathwatch beetles can also attack books (Fisher, 1937; Hickin, 1963a). In the United States, X. rufovillosum is much less important as a pest than it is in Europe. It is common in certain parts of eastern North America, but not along the Pacific Coast (Linsley, 1943b).
Description. The deathwatch beetle adult (figure 115, B) is about 7 mm long, dark grayish brown, with a pattern of yellowish, scalelike hairs on the pronotum and elytra; if the elytra are old and worn, the beetle may appear more reddish and shining (Hickin, 1963b). Xestobium rufovillosum does not have longitudinal rows of small pits on the elytra, such as are present in the furniture beetle, Anobium punctatum. The antennae are 11-segmented, but much shorter than those of A. punctatum, and the last 3 segments are somewhat enlarged and as long as the preceding 5 combined (White, 1962). Circular emergence holes of the deathwatch beetle are about 3 mm in diameter - about twice as large as those of the furniture beetle. The frass consists of relatively large lenticular or "bunshaped" pellets, characteristic of the species (Parkin, 1933).
The creamy-white larva of the deathwatch beetle is the largest of the anobiid larvae, being up to 11 mm long. The head is yellowish, and the mandibles are nearly black. The eyes consist of 2 black spots on each side of the head, compared with 1 black spot in A. punctatum larvae. Spinules occur dorsally on the first 8 abdominal segments, and laterally and ventrally on the ninth and tenth segments. Unlike the spiracles of A. punctatum, those of X. rufovillosum have a very short, tubular projection or air tube (Parkin, 1933).
Life Cycle. In England, where the deathwatch beetle has been investigated extensively, the adults begin to appear in April and May, and their tapping noise is then commonly heard. Unlike the furniture beetle, the adults may remain in their pupal cells until the following spring. They mate soon after emergence, and then die in a few weeks.
The female lays her eggs in small clusters, usually of 3 or 4, on rough surfaces, in cracks, or just inside the emergence holes. When first laid, the eggs are sticky and adhere together. They are whitish, oval, smooth throughout, and about twice as large as those of the furniture beetle. Usually, 40 to 60 eggs are laid, but up to 201 have been recorded. They hatch in 2 or 3 weeks. Under favorable conditions of food and temperature, the deathwatch beetle may go through its life cycle in a year, but this period may be prolonged to as much as 10 years. Outdoors, in oak infected with fungi, the life cycle has varied in duration from 3 to 7 years, and indoors it is believed to average about 4.5 years (Hickin, 1963a).
The eastern deathwatch beetle, Hemicoelus carinatus (Say) (=Hadrobregmus) (figure 115, C), is reddish brown to blackish brown, and is 3.4 to 6.8 mm long. The antennae are 10-segmented, with the last 3 segments (club) as long as or longer than the pronotum in the male, but shorter than the pronotum in the female. It is widely distributed in eastern North America, and has been recorded from ash, basswood, maple, beech, and elm, and in sills, joists, beams, and flooring. The larvae often cause much damage (Payne, 1936; Linsley, 1943b; Craighead, 1950; Wright, 1959). Payne called attention to the fact that the damage caused by H. carinatus resembled that caused by lyctid beetles in hardwoods, except that the emergence holes were a little larger and the frass was somewhat coarser.
The Cailifornia deathwatch beetle, Hemicoelus gibbicollis (LeConte) (=Hadrobregmus) (figure 117), is similar in appearance to the eastern species, but has 11-segmented antennae, and the pronotum is distinctly narrower than the base of the wing covers, whereas in Hemicoellis carinatus they are about the same width. Linsley (1943b) stated that the California deathwatch beetle bred in old, well-seasoned Douglas-fir studs, joists, and supporting timbers along the Pacific Coast, and was especially common in basement timbers of buildings 20 years old or more figure 118). Hatch (1946) found serious damage from this species to the weathered boards of spruce in the flooring of a porch. In the areas where it occurred, Linsley considered H. gibbicollis to be the most serious pest among the powderpost beetles in the broad sense of the term.
Ernobius mollis (L.) appears somewhat like a large Anobium punctatum. The short, golden hairs of the newly emerged adult produce a light shade of golden brown, but when some of the hairs are lost, the beetle becomes more uniformly brown. The elytra are less horny, and lack the longitudinal rows of pits characteristic of A. punctatum. Ernobius mollis oviposits only in softwoods, and then only when the bark is attached. Hickin (1963a) found that when the bark was stripped off, the infestation rapidly died out. In the United States, however, E. mollis occasionally does much damage to pine and spruce flooring (Craighead, 1950).
White (1962) listed 7 species of Ernobius occurring in the eastern United States, including E. granulatus LeConte. This species has unusually large eyes. It is 2.3 to 4.3 mm long, reddish brown, with elytra yellowish apically, appendages and abdomen yellowish brown, and with a very fine, short, yellow pubescence. The last 3 antennal segments are very long. Ernobius granulatus has been recorded from many eastern states.
Despite the usual propensity of anobiids to attack old, seasoned wood, some species can destroy weakened shoots of young pine trees, and are scavengers in the cones of conifers. In California, the species most commonly involved is Ernobius punctulatus (LeConte). The beetles are most abundant where dead pine branches have been allowed to accumulate (Doane et al., 1936).
Priobium sericeum (Say) (= Trypopitys) (figure 115, D) is 4.9 to 6.2 mm long, with the head deeply retracted within the prothorax. It is reddish brown to brown, covered with a short, yellowish pubescence. Antennal segments 3 to 7 are distinctly serrate, 8 to 10 are somewhat serrate, and segment 11 is rather narrow and elongate. The combined length of the last 3 segments of the antennae equals the combined length of the 5 or 6 preceding ones (White, 1962). This species is occasionally found in flooring, sills, and in buildings in the eastern states.
In southern California, Priobium punctatum (LeConte) (= Trypopitys), a species closely resembling the furniture beetle, Anobium punctatum, has been found on oak door casings and flooring and in maple wainscoting. This species has also been found in Monterey cypress and pine (Doane et al., 1936).
Ptilinus ruficornis Say (figure 115, E) is 2.8 to 4.8 mm long. The male is completely black, or black with light-brown elytra. The female is bright reddish brown to dark reddish black, with the pronotum bright reddish brown. Both sexes have reddish-brown to reddish-yellow appendages. The antennae of the female are distinctly serrate, whereas those of the male are actually branched, with each branch, on segments 5 to 10, nearly or quite as long as the combined length of segments 1 to 10. The pronotum of both sexes is roughened anteriorly, but particularly so in the female. This species infests beech, maple, oak, sycamore, mesquite, and other hardwoods, and is a rather common and injurious pest of woodwork and of stored wood products (Craighead, 1950). In California, another species, Ptilinus basalis LeConte, along with the bostrichid Scobicia declivis, attacks California laurel (Umbellularia californica) so readily that laurel has had to be nearly abandoned for interior finishing, for which this very beautiful wood is well suited (Doane et al., 1936).
Xyletinus peltatus (Harris)(figure 115, F) is 3.4 to 6.3 mm long, reddish brown to brown, with a fine, short, yellowish pubescence. Its eyes are large, those of the male separated by about 2 times, and those of the female about 3.3 times, the width of the eye as seen from the front. The 11-segmented antennae are moderately serrate, and the last 3 segments are slightly enlarged. The elytra are finely, not deeply, striate (furrowed), with the interval between striae feebly convex (White, 1962).
Xyletinus peltatus is widely distributed throughout the eastern states, and is the most frequently collected species of the genus (Wright, 1959; White, 1962). Williams (1973) considered it to be the most common anobiid in the southeastern states. It often does great damage to cellar joists and flooring in damp buildings, particularly when they are unoccupied or closed up. This species appears to require moist conditions and associated fungi. When conditions are optimum, it can attack both softwoods and hardwoods so severely that complete structural failure will occur. However, it has been known to manifest distinct preferences for certain wood species. Williams (1973) gave an example of such a preference in lumber stored in an old earthen-floor barn infested with X. peltatus. The wood species were yellow poplar, cypress, and western pine. The cypress and western pine were not infested, but radiographed sample boards of yellow poplar contained an average of 72 larvae per sq ft (929 sq cm), and yellow-poplar molding contained about twice that number.
Prevention and Control of Powderpost Beetles
The following discussion pertains to infestation by the true powderpost beetles (Lyctidae), false powderpost beetles (Bostrichidae), and deathwatch beetles (Anobiidae). Prevention of losses from these beetles should begin at the lumbermill, and be continued in lumberyards, builders' lots, and other areas in which lumber may be stored before use.
An extremely important phase of prevention is sanitation. In nature, beetles breed in old and dried wood, such as dead branches and limbs of trees, and material of this kind should be burned if it exists near piles of lumber. The same may be said of old lumber and other materials that are subject to infestation. Storage areas should be inspected periodically. Infested lumber should be burned, and pallets, stacking sticks, stakes, platforms, and shelves should be protected against attack. Paraffin wax, varnish, shellac, and paint will fill the pores in which lyctid beetles lay their eggs, and thereby prevent infestation. Infestation by lyctid beetles can be avoided merely by using only softwoods for the pallets, stacking sticks, etc. However, oak is preferred, despite its susceptibility to attack, because it is stronger, more durable, and does not shatter or splinter so easily as coniferous woods.
Firewood stacked outdoors is frequently a source of beetles that can infest structural wood after the firewood has been carried into the house. Other woodborers that may not be able to infest seasoned wood, but are nevertheless nuisances and sources of anxiety when found crawling or flying about in the home, can also emerge from firewood.
Green lumber can be protected against powder-post beetles by submerging it in an insecticidal cold-water emulsion. Similar protection for seasoned wood can be obtained with a solution of insecticide and deodorized kerosene. Insecticides that have proved to be effective in this connection are 5% toxaphene, 2% chlordane, 0.5% dieldrin, and 0.5% lindane. Immersion for 3 minutes gives protection for at least 3 years. A 5-minute dip in 5% pentachlorophenol in a light fuel-oil base is also said to be effective, and this same compound, added to the insecticide emulsions or solutions just mentioned, acts as a fungicide. Protection for 1 season can be obtained with only a 10-second immersion in these insecticides or a 15-second dip in a 5% borax solution heated to 180 °F (82 °C). Following any of these treatments, the treated lumber or wood products can be painted or varished after a reasonable drying period (NPCA, 1961).
Some homeowners would certainly not want to have insecticide-treated lumber used for such articles as kitchen cabinets and baby cribs. A concentration of 0.3% dieldrin or aldrin added as an emulsifiable concentrate to glue prepared for plywood manufacture has been found to provide good protection of plywood against Anobium punctatum in New Zealand (Harrow et al., 1970).
All stages of lyctid beetles can be killed by heat in kilns. In table 3, the periods of exposure of wood of various thicknesses that are required to check damage by powderpost beetles at different temperatures and relative humidities are given. The required periods of exposure increase with increasing thickness of the wood, decreasing temperature, and decreasing relative humidity (St.George, 1970).
The type of treatment selected for control of powderpost beetles will depend on a number of circumstances, among them the size of the infested area. If the infestation is localized, the application of a toxic solution to the infested wood surface or a liquid gas volatilized under a tarpaulin may be considered. Infested furniture can be fumigated in a gastight fumatorium. For the treatment of a large infested area, such as an entire house, tent fumigation, such as practiced for dry-wood termite control, may be the only practical procedure. Even if one finds only a few beetles, believed to be a localized infestation, a complete fumigation of the entire structure is the most reliable way to control the infestation. It is often difficult to locate incipient infestations. However, even with complete fumigation of a building, incomplete control of lyctid beetles occurs in about 10% of the treatments.
For treatment of raw hardwood flooring, unfinished paneling, or structural timbers already infested with powderpost beetles, 2% chlordane or 5% lindane, dissolved in a moderately volatile light oil such as deodorized kerosene, have been successful when sprayed or painted on the wood at 1 gal per 100 sq ft (4 L per 9 sq m) of surface or until the wood can no longer absorb the liquid. (Solutions of 5% DDT and 0.5% dieldrin are no longer registered for this purpose.) On finished wood, the entire surface should be treated evenly with a coarse, fan-type spray, but not to the point of runoff puddling. Repeated applications may be necessary to obtain absorption of the recommended quantity. Each successive application should be made after the preceding one has been absorbed, but before the surface is completely dry. Unless the treatment is applied to thew ground floor, care should be exercised to avoid staining the ceiling and walls below the treated floor. Treated floors should not be walked on, and no objects should be placed on any treated surface for at least 24 hours. Since the treatment can destroy wood finishes, it is advisable to treat a small, inconspicuous area for preliminary observation before treating infested finished wood. Damaged surfaces must be resanded, refinished, and rewaxed. Sanding, of course, can also be done before treatment, particularly if the floor happens to need it. A few beetles may occasionally emerge after treatment, but the toxic residue will prevent reinfestation. When parquet or block flooring is bound to concrete slab by adhesive, the oil carriers for insecticides can deteriorate the adhesives. In such cases, the entire building should be fumigated.
Smith (1968) was able to prevent infestation of ash lumber by Lyctus powderpost beetles during air-drying, which commonly requires 3 to 18 months. Ash is highly susceptible to infestation. Boards were dipped in lindane emulsions of various concentrations for 10-second periods and then stood on end in a rack to dry for 1 hour. Twenty boards, 1.2 m long and 10 to 20 cm wide, were used for each lindane concentration. The boards were then placed in stacks, with 1.5-cm pine spacers between them to keep them apart. About 12 months after treatment, the boards were exposed to infestation by introducing infested boards from laboratory-reared colonies. All surfaces were examined annually. With 0.06% lindane emulsion, the number of Lyctus beetle holes varied from none the first year to 6.5 the third year, compared with 22 and 295, respectively, in the untreated controls. At 0.25% concentration of lindane, no holes were found during the 3-year period. Since the normal storage period was not longer than 18 months, Smith concluded that a 10-second dip in 0.06% lindane emulsion was adequate for protecting lumber from Lyctus beetles during air-drying. A 25% increase in lindane concentration sufficed for protection against ambrosia beetles, which are discussed later.
For the treatment of timbers such as those used in log cabins, rustic bridges, rustic furniture, and the like, a 0.5% lindane solution in petroleum oil, sprayed onto the surface of the bark or wood, is effective for the control of bark beetles or borers that have only recently attacked and have not penetrated deeper than the outer surface of the wood. Wood that has been attacked for a longer period should be soaked for at least 5 minutes.
Toxic Solutions for Anobiid Beetles
Anobiid infestations usually begin in crawl spaces, particularly if the soil is wet, for the wood then contains more moisture, favoring infestation. Fortunately, the infestation spreads slowly. Control is least difficult and least expensive when the beetles are still confined to the substructure and before they have spread upward into the walls (Williams, 1973). Extensive research was done by Spink et al. (1966) at Louisiana State University on the control of the anobiid Xyletinus peltatus. The external signs of infestation by this beetle were entrance holes less than 1.6 mm in diameter and exit holes about 3 mm in diameter. The number of holes might exceed 200 per sq ft (929 sq cm). Dieldrin at 1% and chlordane at 2% concentrations, in either water or kerosene, gave complete control when applied with a 1-gal (4-L) compression sprayer to the inner sides of 2 joists and the subflooring between them. The liquids were sprayed back and forth over the infested wood until no more liquid was absorbed. There were 4 replications of each treatment. Pretreatment and post-treatment evaluations were based on the number of pellets falling from the infested areas. The tests were stopped after a year.
Another test was made in 6 houses. Dieldrin at 0.15% and 1% and chlordane at 1% and 20% concentrations in water or kerosene were applied to subfloor wood members infested with Xyletinus peltatus. The liquids were applied with a motorized 15-gal (57-L) sprayer, with pressure held to a minimum. The spray was applied in a solid, cone-type pattern, using a No. 5 nozzle disk with a 2-mm aperture. The sprays were applied back and forth over the wood until the timbers were saturated. Approximately 4 gal (15 L) of kerosene solution or 4.5 gal (17 L) of water solution were required for treating 100 sq ft (9 sq m) of infested wood surface. No spreaders or stickers were added to the spray liquids because the tests were made to determine whether sprays as used for termite control and applied with similar equipment, but with reduced pressure, could control anobiid beetles. Evaluations of efficacy were made as in earlier tests, and no further evidence of infestation was seen after any of the treatments.
When the beetle larvae bore into wood, they fill their entrance holes with frass. Tests with water-soluble dye have shown that the frass acts as a wick to carry the insecticide deeply into the wood.
Fumigation for Powderpost Beetles
Methyl bromide fumigation for drywood termites was discussed under the heading "Fumigation." Fumigation for powderpost beetles can be done in the same way, but instead of a concentration of 2 lb per 1,000 cu ft (0.91 kg per 28 cu m) of building space, 3 lb (1.36 kg) is generally recommended for a 24-hour period, provided the temperature is over 60 °F (16 °C), the space being fumigated is properly sealed, and a minimum of 0.5 lb per 1,000 cu ft (0.23 kg per 28 cu m) of gas remains at the end of the 24-hour period of fumigation. Under some circumstances, a higher initial dosage or additional gas sometime during the fumigation period may be required. Methyl bromide fumigation should be done only by a licensed and experienced operator.
Movable items such as furniture can be fumigated in vaults or fumatoriums designed for this purpose. Some pest control firms have such facilities (figure 119). Because of tighter sealing and controllable temperature, either the dosage or exposure can be decreased below that which is required for effective building fumigation. For vault fumigation with methyl bromide, the usual relationships of dosage and period of exposure are, per 1,000 cu ft (28 cu m): 1 lb (0.45 kg) for 24 hours, 3 lb (1.36 kg) for 8 hours, or 9 lb (4.08 kg) for 3 hours. When it is possible to provide partial vacuum, dosage or time can be even further decreased (NPCA, 1961).
Beetle-infested timbers may also be placed in a pile, covered with a tarpaulin, and fumigated with methyl bromide at the rate of 4 lb per 1,000 cu ft (1.82 kg per 28 cu m) of air space. The gas should be confined for about 72 hours. Methyl bromide is an odorless gas and deadly poisonous if inhaled (St. George, 1970).
Sulfuryl fluoride (Vikane), often used for fumigation of drywood termites, is not recommended for control of lyctid beetles because of its relatively low efficacy against the eggs. About 10 times the dosage used in drywood termite fumigation is required to kill lyctid eggs.
An aluminized, neoprene, portable, gastight fumigation tent, with walls and floor continuous, and supported by a collapsible tubular metal pipe frame (figure 120) was developed in England for on-the-spot fumigation of small commodities. It is 7 ft wide, 7 ft high, and 9 ft deep (about 2 m and 2.75 m) and has a 300-cu ft (8.4-cu m) capacity. It has 2 types of gastight seals for the front opening: an industrial metal zipper or a pressuretight channel that completely seals all edges of the flexible flap opening. A 10-in. (25-cm) fan is operated in the tent for a period of 3 minutes, immediately after the fumigant is introduced, to thoroughly distribute the gas (Burns Brown and Heseltine, 1964). A metering device is supplied with the tent that delivers the entire contents of a 1-lb (0.45-kg) can of methyl bromide, supplying a concentration that is the equivalent of a little over 3 lb per 1,000 cu ft (1.36 kg per 28 cu m). As stated above, in vault fumigation the period of exposure for this concentration of methyl bromide is normally 8 hours.
If a lower rate of dosage is required for the commodity fumigated, a shorter exposure period should be utilized, rather than using less gas.
Fumigation is very expensive, and when an infestation of powderpost beetles is known to be confined to a section of hardwood flooring, a localized treatment may be appropriate. S.T.D., proprietary 15.17% solution of the liquid fumigant ethylene dibromide and 4.03% chlordane, in deodorized kerosene, may be mopped evenly over the infested area, using just enough to wet it without leaving puddles. On upper floors, care must be taken to avoid using so much liquid that some of it will stain the ceiling below. The treated area is covered with a polyethylene tarpaulin, the edges of which are taped down to the dry floor surrounding the wet area, and the tarp is left in place for 24 hours. It is then removed, and the windows are opened to allow for complete ventilation.
Occupants are kept out of the room(s) being fumigated during this 24-hour period and the additional period required to completely remove the gas (Ehmann, 1961; NPCA, 1961). Repeated treatments may be required, but pest control operators in the Los Angeles area advise us that the surprisingly few "callbacks" after localized treatment for powderpost beetles indicate to them that their treatments are generally successful. Such pest control operators usually offer a 1-year guarantee on their work.
In another form of localized treatment for powderpost beetles, some pest control operators place a tarpaulin over infested areas, such as hard wood wall cabinets, and release methyl bromide under the tarp.
The localized treatment with ethylene dibromide, when properly performed, usually will not harm a varnished floor surface but will dissolve the wax coating.
In cases where parquet or block flooring is laid directly on a slab to which it is bound by adhesive, the liquid fumigant should be applied in a pan under the tarp so that the ethylene dibromide will contact the floor only as a gas and not as a liquid; otherwise, the adhesive under the floor may be dissolved. Plywood is more difficult to penetrate with a gas because of the glue layers, and increased dosages and extremely careful application techniques are required to ensure good results.
The homeowner may decide to consider removal and destruction of infested wood as an alternative to fumigation (NPCA, 1961).
ROUNDHEADED BORERS (CERAMBYCIDAE)
Roundheaded Borer Species List
- Newhouse Borer, Arhopalus productus (LeConte)
- Oldhouse Borer, Hylotrupes bajulus (L.)
- Wharf Borer, Nacerdes melanura (L.) (Oedemeridae)
The family Cerambycidae includes many species of large, slender, woodboring beetles. The adults usually have very long antennae that may be much longer than the body, giving them the common name, "longhorned beetles." The 2 most important cerambycid pests of buildings, the newhouse borer and oldhouse borer, do not have particularly long antennae. All adult cerambycids have large, strong, toothed mandibles.
The larvae are somewhat cylindrical, and have a large and fairly cylindrical thorax, resulting in burrows of a similar shape in the infested wood, hence the name, "roundheaded borers." The larvae have small heads, but powerful mandibles. Larval legs are lacking or vestigial.
Newhouse Borer, Arhopalus productus (LeConte)
The newhouse borer is a cerambycid beetle found throughout most of the western United States and western Canada. It occurs in pines and firs, but particularly in Douglas fir ("Oregon pine" of lumbermen). It breeds in dead or dying trees, and is especially abundant in fire-swept areas, probably being attracted to the trees mainly during the first summer after a fire. When lumber from such trees is used for building houses, the emergence holes of the adults may appear in hardwood flooring, linoleum, plaster, plasterboard, or composition roofing.
Biology. The adult (figure 121) is a narrow, black beetle, 2 to 3 cm long. The larva is yellowish white, and is about 4 cm long when full grown. The female lays eggs in deep crevices of the bark.
Because the bark has been removed, the female does not oviposit in wood that has been converted into lumber. Therefore, there is no danger of reinfestation from beetles that have emerged (Wood, 1964). In trees, the larvae initially tunnel at the juncture of sapwood and bark. Later, they tunnel entirely in the sapwood, and finally move into the heartwood. They always pack their tunnels tightly with fibrous frass. If 2 pieces of recently cut lumber are in contact with each other, the larvae sometimes tunnel from one piece into the other. In isolated pieces of lumber, the larvae occasionally bore to the surface, plug the hole, and continue tunneling in the interior. The fullgrown larvae construct large pupal cells, and when the adults bore their way out of the wood, they make clean-cut oval holes at the surface about 6 mm in diameter. These are easily distinguished from the circular holes made by emerging woodwasps. Also, surrounding each emergence hole of the newhouse borer there is usually an accumulation of long drillings that looks like a pile of cigarette tobacco.
Duration of Infestation. Although it takes at least 2 years for the newhouse borer to complete its life cycle, the appearance of adults in a house may occur within a few months after construction is completed, and rarely after 1 year. The reason appears to be that as the wood dries out, it becomes unsuitable for larval development. Only those larvae that are nearly full grown are able to survive and reach maturity under these dry conditions (Eaton, 1959).
Types of Lumber Infested and Extent of Infestation. Apparently, the most commonly infested lumber is Douglas-fir subflooring. Any material, such as hardwood flooring or other floor covering on the infested lumber, may be perforated in order to provide an escape route for the emerging adult. Eaton and Lyon (1955) once found 1 to 8 (average 4) visible emergence holes per house in a tract in which there was some evidence that the Douglas-fir subflooring had come from a fire-killed stand of timber. The beetles sometimes emerged from infested wood framing in the walls or ceilings of buildings, or from sheathing. In one building, 34 exit holes were counted in the plaster. The infestations are never extensive enough to cause serious mechanical weaknesses in a structure. Nevertheless, the holes, just as those caused by woodwasps, may be causes of consternation and worry for the homeowner.
The incidence of infestation by such insects as the newhouse borer and woodwasps has increased in recent years. This is because of the increased demand for wood, which has made it profitable to cut timber that in past times would have been rejected, particularly since this kind of timber can be obtained at little or no cost. It is perfectly sound for structural purposes. Air-drying of the lumber for over 1 year, or kiln-drying, would solve the problem, and the complete use of such timber would result in a greater utilization of our natural resources.
Western lumber destined for eastern markets is generally kiln-dried because removal of water decreases its weight. Beetles and other insects are killed by the process. Lumber harvested in the West which is to be used on the West Coast is often air-seasoned for just a few weeks. To allow a long period for air-seasoning and storage would likely cause the death of most wood-infesting insects, but increase the cost of production.
Control of the Newhouse Borer
Wood (1964) pointed out that radiographic techniques were available, so that the presence and extent of woodborer infestations in finished lumber could be determined. It may be desirable to use this technique before investing in an expensive control measure, such as fumigation. Fumigation with methyl bromide gas has been successful in the United States and Europe for the control of the oldhouse borer, Hylotrupes bajulus, which has habits similar to those of the newhouse borer and does similar damage. Therefore, it is reasonable to suppose that methyl bromide can be successfully used against the latter species.
Infestation of a building by newhouse borers is seldom, if ever, sufficiently severe to justify the ,great expense of fumigation. Filling of exit holes or repair of damaged areas after the adults have emerged is the most economical solution. In any case, by the time the infestation has been detected it is often too late for any measures aimed at the destruction of the insects themselves.
Oldhouse Borer, Hylotrupes bajulus (L.)
The oldhouse borer apparently originated in northern Europe, where it has been found in 40 to 50% of the houses in some surveys. It has spread from there to many parts of the world, including most of the states of the Atlantic seaboard and in various other areas as far west as Minnesota and Texas. An August mean temperature of about 73 °F (23 °C) is an important factor favoring the development of the oldhouse borer, and might be a useful criterion in predicting the future distribution of the beetle in North America (Anonymous, 1967c). There are well-documented records of the oldhouse borer having been transported to new areas in infested wooden boxes and packing cases. From France, the insect was transported to England in pine flooring, and to Australia, in the pine framing of prefabricated houses (NPCA, 1965). Thus, while this serious pest has not yet been established in the western United States, there is no reason to believe it could not be accidentally introduced.
Unlike the newhouse borer, the oldhouse borer can be present in old houses as well as new ones and, most importantly, can reinfest timbers from which it emerges. It can thus cause great structural damage.
Korting (1962) stated that lumber in houses 60 years and more of age was less subject to infestation than in new houses. Moreover, adult female beetles in the older houses are smaller and have fewer progeny. Patton (1931) reported that, in Denmark, roofs of timber covered with metals more than 20 years were most subject to attack. Houghton (1939) stated that in the United States, H. bajulus was most likely to attack attic and roof timbers, but infested framing and flooring also. In Norway, H. bajulus was found mainly in attics, and only in districts of the highest mean temperatures and the longest periods of relatively high temperatures during the summer (Knudsen, 1967). In Massachusetts, houses that are centuries old, some of historic interest, are being infested. Sometimes the infestations are so severe that the occupants of infested houses hear "gnawing" or "clicking" sounds that are caused by the beetles (Becker, 1954). Like the newhouse borer, the oldhouse borer attacks only softwoods, feeding mainly on the sapwood, but the adults may bore through other types of wood or plaster in order to emerge.
Whereas both Arhopalus productus and Hylotrupes bajulus can be introduced into a building in infested lumber at the time of construction, of the 2 beetles only H. bajulus can infest the building after construction. At least in the United States, it is strictly a structural pest, and has not been found in logs and stumps (Snyder, 1955a), presumably because it is an introduced species that has not yet become established in nature. [Another species, H. ligneus (F.), has been found damaging rustic furniture in cabins (Thompson, 1932).] Although infestation by H. bajulus can occur wherever susceptible wood is present, in the United States the majority of infestations are said to be in attic framing in the northeastern area and in the substructure along the mid-Atlantic Coast (NPCA, 1965).
Description. The adult females of
Hylotrupes bajulus may reach a length of 2.5 cm, but the males are only about half as long. The adults are slightly flattened, grayish black to very dark brownish black, with many gray or yellowish-gray hairs on the head and anterior part of the body. However, these may be rubbed off on older specimens. Two elevated black, shiny knobs on the prothorax give the dorsum an appearance like a face with a pair of eyes (figure 122). About a third of the way posterior on the elytra, and centrally located, there are 2 grayish, transverse marks.
The full-grown larva (figure 122) is grayish white, from 2 to 4 cm long, has a broad thorax, and tapers posteriorly. There are deep folds between the abdominal segments, and there is a deep groove running lengthwise in the center of the prothorax. There are 3 black ocelli in a row on each side of the very small head, but a hand lens is required to see them. The stout, very dark jaws are relatively prominent. The pupa is about the size of the adult, and is at first creamy-white and then becomes light brown.
About 150 to 200 white to grayish-white, spindleshaped eggs about 2 mm long are laid in checks, cracks, crevices, or irregularities of the wood. Stacks of lumber are said to be excellent oviposition sites. It takes 2 or 3 weeks for the eggs to hatch. The larvae feed in the dry sapwood from 2 to 10 years (usually 3 to 5) until the sapwood is completely destroyed. They fill their mines loosely with frass composed of tiny pellets and fine, powdery material. The frass occupies a greater volume than the wood from which it was produced, and this causes the surface of the infested wood to have a blistered or rippled appearance (Hickin, 1963a). A rhythmic rasping or chewing sound made by the larvae may be the first indication of their presence, for their tunnels seldom break through to the surface, even though the interior may be severely mined.
Life Cycle. The adults may remain in the tunnels prepared by the larvae for 7 to 10 months before emerging, but then live for only a brief period. They appear in the summer, and oviposition takes place at that time. In the United States, the period required for the life cycle of the oldhouse borer may be from 3 to 5 years in the southern states, whereas northward from the latitude of Washington, D.C., an additional 2 to 3 years may be required. Most of the period is spent in the larval stage, for the egg and pupal stages each last only about 2 weeks, and the adults live 8 to 16 days. The majority of adults fly in June and July. Adult beetles often emerge from attic timbers a year or two earlier than from basement wood in the same building, because of the higher attic temperatures (Patton, 1931; Craighead, 1950; St. George et al., 1957; Hickin, 1963a; McIntyre and St. George, 1961).
Signs of Infestation
There are a number of indications when oldhouse borers are active in a building. In the early stages of an infestation, the rasping or ticking sounds made by the larvae while boring may be heard, or a blistering of the wood when the larva works close to the surface may be seen. If the wood surface is probed where tunneling is suspected, the larvae or their powdery borings may be located. Only after the buildings are at least 3 to 5 years old in the southern states, or 5 or more years old northward from the latitude of Washington, D.C., will the emerging adults, or their 7-mm, broadly oval emergence holes, be evident (McIntyre and St. George, 1961).
Relation of Protein Content to Susceptibility of Wood to Attack
Becker (1963) determined that a minimum of 0.2% of protein was required, in the softwoods investigated, to support an oldhouse borer population. From that point, larval development increased in direct proportion to an increase in protein content. The suitability of the wood for the development of larvae decreased as it aged, probably because of a change in the nutritive value of proteins during storage, a decrease in vitamin content, and other chemical or structural changes in the wood. The suitability of the wood for larval development could be fully restored by the addition of protein and vitamin B. Nevertheless, as just stated, some very old buildings are being severely attacked. The older the building, the greater the chance that it may have an infestation, despite the decreasing nutritional value of the wood.
During the first stages of decay, wood infected by wood-destroying fungi, such as Lenzites, shows an increase in protein content and becomes more favorable for larval development. Likewise, pine wood contains more protein than spruce, and in areas of Europe where pine is widely used in construction, oldhouse borer infestations are more frequent and severe than in areas where spruce predominates. A reduction in quantity and quality of protein and a loss of vitamin B can be quickly accomplished by artificially applied gamma radiation. This suggests a new approach to the protection of wood from attack by the oldhouse borer (Becker, 1963).
Larvae of the oldhouse borer were unable to develop in 4 commonly used types of fiberboard, whereas termites (Reticulitermes, Heterotermes, Coptotermes, and Kalotermes) were able to attack and destroy them, and chemical preservatives were required to protect them from termite attack (Becker, 1969b).
Control of the Oldhouse Borer
In both Europe and the United States, fumigation of infested buildings is considered to be an effective treatment for Hylotrupes bajulus infestations (Rasmussen, 1967; McIntyre and St. George, 1961), but of course fumigation leaves no protective residue. Methyl bromide at 3 lb, or HCN gas at 2 lb per 1,000 cu ft (1.36 or 0.91 kg per 28 cu m) has been used satisfactorily (St. George et al., 1957). Fumigation must be done only by qualified pest control operators. Borer larvae can be killed by applying 2% chlordane in deodorized kerosene to the infested wood with a brush or, for larger areas, a sprayer, applying the liquid at the rate of 1.5 pt per cu ft (0.71 L per 28 cu dm) of wood treated. For example, one would apply 1.5 pt to 12 linear ft of a 2 x 6-in roof rafter, or 18 linear ft of a 2 x 4-in. stud, or 12 sq ft of subflooring. [Metric equivalents: 0.71 1 per 28 cu dm; 0.71 L to 3.65 linear m of a 5 x 15-cm roof rafter; 5.5 linear m of a 5 x 10- cm stud; about 1.10 sq m of subflooring.] Wood absorbs kerosene solutions when it is dry and the temperature is at least 80 °F (27 °C). For spot treatments, 0.50% lindane may be used instead of the chlordane solution. If the infested wood does not at first absorb the required quantity of toxic solution, the treatment must be reapplied until the necessary quantity has been absorbed. The solution will not penetrate properly if the wood has been painted, varnished, or waxed. Unlike fumigation, treatment with toxic solutions is not only a control but also a preventive (Mclntyre and St. George, 1961).
In South Africa, similar solutions have been applied on infested timbers, but lumber used to replace timbers structurally damaged by Hylotrupes bajulus was impregnated with a preservative such as copper naphthenate or zinc naphthenate, preferably applied by vacuum pressure (Durr, 1956).
The pentachlorophenol emulsion Woodtreat-TC, which has been used successfully against subterranean and drywood termites in structural timbers, may also be effective against newhouse and oldhouse borers (Ebeling, 1968).
Any insect that infests old, weakened, or fire- or insect-killed trees is likely to be incorporated into buildings constructed from lumber obtained from such trees if it is not kiln-dried. Among such insects are many species of cerambycids besides those already discussed.
One of the most conspicuous and best-known species found in lumber is Ergates spiculatus (LeConte) (figure 123, A), a large, slender beetle, 4.5 to 6 cm long, reddish brown, with head and thorax darker than the elytra. The lateral margin of the prothorax is armed with a few large and many small, sharp spines. The adults are often attracted to lights. The creamy-white larvae are 5 to 7 cm long. According to Linsley (1962), E.spiculatus "not only attacks the wood of recently killed or felled trees, but also fallen logs, stumps, and power and telephone poles," and "has often ruined fire-killed Douglas fir before salvage operations could begin." This species occurs throughout western North America.
Another cerambycid, the black pine sawyer, Monochamus scutellatus (Say) (figure 123, B), is 1.6 to 3 cm long and shining bronzy black, with a white scutellum, coarsely punctured, a large median "tooth" on each side of the prothorax, and very long antennae, often twice the length of the body. It is widely distributed in the coniferous forests of North America, and is especially abundant in timber following burns (Chamberlin, 1949). The spotted pine sawyer, Monochamus maculosus Haldeman, may reach a length of 3 cm or more, with antennae 2.5 times the length of the body. These beetles are brown, with bluish-gray dorsal spots. The prothorax has a prominent median tooth on each side. The larvae are very destructive to both heartwood and sapwood of dying, fire-scorched, and recently felled pines in the western states. The black timberman, Monochamus oregonensis (LeConte), ranges from British Columbia to southern California and east into the Rocky Mountain states, sometimes causing losses to fir logs exceeding 10 to 20% if they are left in the woods a few months. This species is 2.5 to 4 cm long, and has a cylindrical, deeply and coarsely punctured body. The color is uniformly black, sometimes with a bronzy reflection, and the scutellum is white. Silvery-white spots are sometimes scattered over the elytra and on the thorax and antennae (Chamberlin, 1949).
The banded alder borer, Rosalia funebris Motschulsky, is one of the best-known and most attractive of the Pacific Coast cerambycids. It is 2.5 to 4 cm long, marked with black and white as shown in figure 123, C, and has very long antennae that are annulated with black and white. It breeds in ash, alder, and California laurel and, east of the Sierra Nevada, generally in willow. According to Doane et al. (1936), this species is responsible for the hollowing-out of the trunks of many of the larger laurel trees in California. It is mentioned here mainly because of its conspicuous and striking appearance, resulting in many requests for identification. However, during periods of very high temperatures, the beetles are attracted to recently painted dwellings after the paint has become dry, apparently attracted to certain volatilized ketones from the paint. They are present on some buildings in such large numbers as to be a definite nuisance (Chemsak and Linsley, 1971; Essig, 1943).
A common eastern species on hickory, locust, and ash, often attracting attention in resort areas, is the fourspotted longhorn, Eburia quadrigeminata (Say) (figure 123, D). It is 1.5 to 2.5 cm long, light brown to tan, and easily recognized because of the 2 pairs of elevated, ivory-colored swellings on, and the 2 spines at the tip of, each elytron. The life cycle usually requires 2 years, but this species has also been found emerging from flooring, sills, and other wood members 10 to 15 years after the materials were installed (Chamberlin, 1949).
The nautical borer, Xylotrechus nauticus (Mannerheim) (figure 124), is a western species, 8 to 15 mm long, and varies in color from grayish brown to nearly black. It has 3 transverse, zigzag white lines on the elytra, and rather short antennae for a cerambycid. The larva is robust in form, and may attain a length of 18 mm. In California, the larvae may be found in live oak, black oak, and sometimes in eucalyptus and madrone, or in walnut or stone-fruit trees in orchards. It is most frequently encountered in the home emerging from firewood cut from such trees.
Various species of Neoclytus likewise commonly emerge from firewood and are found in homes. This genus is characterized by the many transverse carinae (elevated ridges) on the disk of the pronotum. The antennae are relatively short, as in Xylotrechus, but are more or less clubbed, and the legs are long. Unlike the larvae of Xylotrechus, which have no legs, those of Neoclytus have small legs composed of at least 2 segments (Linsley, 1964). Probably the most common species of Neoclytus on the Pacific Coast is N. conjunctus (LeConte). It has either white or yellow markings on a black background. The pronotum is broadly rounded, the elytral apices are rounded, ancl the head, thorax, and abdomen are hairy (figure 125). It breeds in Oregon ash, various white oaks, madrone, manzanita, eucalyptus, pear, and apple (Doane el al., 1936; Linsley, 1964). Any of these trees cut for lumber should be utilized promptly, otherwise the larvae of N. conjunctus will render the wood useless for anything but firewood. Even the value of the infested timber as firewood is reduced because of the honeycombing of the wood by these beetles. Cordwood should be piled and covered with brush, for shaded wood is not attractive to the beetles (Chamberlin, 1949).
In the eastern United States, 2 species of Neoclytus that emerge from firewood and are sometimes found in houses are N. acuminatus (F.) and N. caprea (Say). Neoclytus acuminauts is 6.5 to 18 min long, reddish brown, with 4 yellow bands across the elytra, and long, reddish legs. It attacks unseasoned wood with bark remaining, and frequently causes serious losses of ash, hickory, and oak logs left exposed during the flights of these insects (Craighead, 1950). Neoclytus caprea is 12 to 15 mm long, deep purple, with 3 yellow bands across the elytra and 3 narrow, yellow bands across the prothorax (Sweetman, 1965). This species sometimes destroys an entire winter clut of ash logs, honeycombing the sapwood with tunnels that are tightly packed with granular frass (Craigheah, 1950).
Wharf Borer, Nacerdes melanura (L.) (Oedemeridae)
This insect, which resembles a cerambycid, is found throughout much of the United States and Canada, particularly in coastal areas, along lake shores, and along major inland waterways. The larvae niay be found in moist timbers, such as wharf timbers, foundation pilings under buildings, in damp cellars or crawl spaces, in wood around leaky faucets, in buried wood, or in any wood that is damp or soggy, and particularly if it is decayed. In England, it has been found in timbers of many barges and wooden-hulled ships sailing in the region of the Thames estuary. In London, the adults have been seen by the "tens of thousands, running over the pavements of the Strand" without their origin being discovered (Hickin, 1963a).
It is not known if wharf borer larvae damage sound wood. They are pests primarily because the adults may suddenly emerge in a building in large numbers and gather around windows, doors, or other sources of light, and thereby become nuisances.
Description. The slender adult is about 10 mm long, and is brown to reddish yellow above, with the tips of the elytra, the eyes, sides of the thorax, legs, and ventral parts generally blackish. There are 3 raised, longitudinal lines on each elytron. The body is covered with a yellow pubescence. The antennae are about half as long as the body (Balch, 1937; Hickin, 1963a). The full-grown larvae are about 3 times longer than the adults, cream-colored, with brown mouthparts, and mandibles that are almost black at the tips. Besides 3 pairs of true legs on the thorax, they have prolegs on the third and fourth abdominal segments. Their legs are larger than those of other wood-boring larvae.
FLATHEADED BORERS (BUPRESTIDAE)
Flatheaded Borer Species List
- Dicerca horni Crotch
- Golden Buprestid, Buprestis aurulenta L.
- Green Buprestid, Buprestis langii Mannerheim
The family Buprestidae is well represented among the timber beetles. The adults are medium to large, usually somewhat flattened, and some are characterized by brilliant, metallic colors with various iridescences. The elytra are usually ridged or roughened. Because of their attractiveness, they are favored by both professional and amateur insect collectors. The larvae lack eyes and legs, are distinctly segmented, and have very small heads and greatly enlarged and usually flattened thoraxes, which latter feature has given rise to the name, "flatheaded borers."
The winding tunnels made by the larvae tend to have approximately the same shape as their thoraxes - about 3 times broader than high. In this respect, the tunnels frequently can be distinguished from the more nearly rounded tunnels of most of the roundheaded borers of the family Cerambycidae. The life cycle of most buprestids usually requires only 1 or 2 years, and is therefore ordinarily completed before the lumber is used, but with several species found in structural lumber, development can continue for a much longer period. Their tunnels, packed with frass, are often seen in softwood lumber, especially in that from trees salvaged after forest fires, windstorms, or bark beetle infestations.
In recent years, buprestid beetle damage to "grapestake" fences has come to our attention. Damaged fences can sometimes be found throughout a newly developed residential tract. If the wood becomes wet, the frass within the burrows expands and extrudes through the oval burrows. This may lead observers to believe that active burrowing is taking place. The wood for such fences was cut from trees that had been infested, but it cannot become reinfested. Buprestid beetles are long-lived, but probably very few of the insects remain in the wood to cause further damage.
Dicerca horni Crotch
This is a common flatheaded borer of the Pacific Coast states. It belongs in a genus of medium-sized buprestids that are characterized by their dull-bronze color and the prolonged tips of the elytra (plate II, 1; figure 126). Dicerca horni is a dark, grayish bronze, 13 to 25 mm long, and has small, black, narrow, broken ridges on the dorsum. The larvae are approximately 2.33 times longer than the adults. This species occurs on many species of deciduous trees (including fruit trees) and shrubs, inhabiting dead or dying trees or dead wood on living trees. Adults may be seen from April to September. This is not a pest, but we receive many requests for its identification.
Golden Buprestid, Buprestis aurulenta L.
The entomologist may receive many more inquiries regarding the golden buprestid than one would expect merely on the basis of its relative importance as a pest. This is because of the striking beauty of the adult beetle, which attracts much attention and curiosity. The adult beetle (figure 127) is about 2 cm long, and golden green or blue-green in color, with the median suture and margins entirely bordered with copper. The larva is white, and about 3.5 cm long.
Life Cycle and Habits. The golden buprestid prefers Douglas fir, but will also attack several species of pine, spruce, and fir, and is occasionally found in western red cedar. The adults generally oviposit on trees, with the bark still on them, that are dying or have been lightning-struck, fire-scorched, or recently felled. They are particularly attracted to resinous wood. They usually, but not necessarily, oviposit on the bark. They can also oviposit on fire scars, in cracks of freshly sawed lumber, and less frequently on older, dry, or partially dried structural lumber. It is believed possible, but probably rare, for beetles emerging from a building to reinfest it. Upon hatching, the larvae bore into the tree, their winding tunnels continuously increasing in size as the larvae grow during the 2 to 4 years required for their development. They readily mine heartwood as well as sapwood. The tunnels are broadly oval, reach a width of about 10 mm, and vary in length from 1 to 5 m. The tunnels are packed with powdery borings, which aids in distinguishing them from the tunnels of cerambycid (roundheaded borer) larvae that are packed with a loose mixture of fibrous and powdery material (Every and Rudinsky, 1962).
The longevity of the larvae of B. aurulenta in furniture and in lumber used in construction is amazing, some having been recorded as living 15 to 20 years (Every and Rudinsky, 1962) and even up to 40 to 50 years or more (NPCA, 1964b). Linsley (1943c) believed that in the many records of such longevity, the chance that the beetles oviposited long after the structures were built was very remote. For one thing, this species, like oiher buprestids, mates and oviposits in the bright sunshine of midday, and is not likely to be ovipositing within a building. Also, in some of the instances of prolonged larval life, the beetles were found in linoleum-covered flooring or boring in kitchen cabinets. As further evidence for infestations originating during construction, an adult emerged from a dresser in Germany, where the species does not occur, 13 years after the dresscr was manufactured, partially from wood of American origin.
Pupation takes place in oval pupal chambers near the surface of the wood. The adults eat their way out of the wood, leaving the typical oval buprestid exit hole. In nature, adults emerge most frequently in spring and early summer, but inside buildings they emerge most frequently between late fall and late spring. The adults live 3 to 5 months (Every and Rudinsky, 1962).
Control of the Golden Buprestid
Infestations of the golden buprestid are not likely to occur in lumber cut from logs removed from the forest soon after they were felled, and which were healthy when cut. The beetles cannot survive in kiln-dried lumber. The insect can survive in air-seasoned 1-in. (2.5-cm) boards, but it is most often reported from 2-in. (5-cm) tongued and grooved Douglas-fir subflooring. Lumber to which bark is still attached is more likely to be infested than bark-free lumber. Wood preservatives will discourage oviposition to some extent (Every and Rudinsky, 1962). Exit holes can be plugged and damaged surfaces can be refinished. Infestations are only occasionally severe enough to cause serious structural weakness.
Green Buprestid, Buprestis langii Mannerheim
This is another attractive beetle (figure 127) that is less common than the golden buprestid, is about the same size, and has similar habits. It is usually bright green, but may be brilliant blue or coppery bronze, the female often with 2, 4, or 6 light spots on the elytra, the tips of which are bidentate. This species breeds in Douglas fir, and does damage similar to that of B. aurulenta in structural timbers, piling, poles, siding, and flooring (Chamberlin, 1949).
BARK BEETLES (SCOLYTIDAE)
Bark Beetle Species List
The Genus Dendroctonus
The Genus Ips
- Western Pine Peetle, Dendroctonus brevicomis LeConte
- Mountain Pine Beetle, Dendroctonus ponderosae Hopkins
- Southern Pine Beetle, Dendroctonus frontalis Zimmerman
- California Fivespined Ips, Ips confusus (LeConte)
Bark beetles are small, cylindrical, robust or slender beetles, usually brown, reddish brown, or black; the head partially or completely concealed from above; the antennae short with a variable number of segments, but usual;y 11 or 12, with the first one enlarged and the terminal 3 or 4 greatly enlarged and fused into a compact knob or club. They are often about 3 mm long, rarely as long as 8 to 10 mm, and are robust in appearance. These beetles are our most serious forest pests, being attracted to weak, injured, dying, or felled trees. Some species attack fruit, shade, and ornamental trees and shrubs. The small larval tunnels, about 1.5 to 3 mm in diameter, can be seen in lumber or in buildings after construction. Scolytids cannot live in seasoned wood.
Among scolytids, only 1 sex selects the individual host tree in which mating and oviposition take place. In Dendroctonus, a monogamous genus, the female excavates the entrance tunnel, and in Ips, a polygamous genus, this is done by the male (Wood, 1970).
Bark beetles tunnel through the bark and then between the bark and the sapwood, often scoring the surface of the latter. The adults excavate brood galleries and lay their eggs in tiny niches at intervals along the sides of these galleries. In some species, the brood galleries may be constructed by a single mated pair of beetles; in others, the male may have a harem of 2 or more females, each of which excavates a brood gallery. Fine, brownish-white, sawdustlike frass is pushed out of the entrances of the burrows by the beetles. The larvae bore out on either side of the egg tunnel, but remain between the wood and the bark, making patterns and engravings that are characteristic for each species (figure 128). The larval tunnels are filled with frass, and become larger as the larvae increase in size. Pupation takes place at the end of the tunnel, and the adults bore out through the bark. The exit holes may be so numerous that the tree appears as if it had been riddled with birdshot.
When the bark is pulled away, the engravings are revealed, but the galleries do not penetrate deeply into the wood. In log cabins, rustic wood furniture, or rustic bridges, the engravings are revealed when loose bark falls off. However, before the bark falls off, the frass (the same color as the underbark), which is made up of small, granular, gritty particles, may fall through cracks in the bark. Adult beetles may emerge from exit holes in the bark for as long as a year after the tree is killed. In structures built of infested logs, they may be found at windows where they are attracted by light. They cannot reinfest the dry bark from which they have emerged (St. George, 1970).
The Genus Dendroctonus
The principal bark beetles in pine forests are species of Dendroctonus and Ips, the first-named being the more important. Twenty-four of the 25 species of Dendroctonus are in North America. The adults are stout, cylindrical, reddish brown to black, and the species vary from 2.2 to 9.5 mm in length. The largest species is the red turpentine beetle, D. valens (LeConte), which is from 5.7 to 9.5 mm long.
Some species of Dendroctonus attack weak, dead, or dying trees, but others seem to prefer normal, healthy trees. Infested trees can be detected because of their fading foliage, the presence of pitch tubes with reddish boring dust on the trunk, or loose dust in the crevices of the bark. Egg tunnels and larval tunnels can be seen between the bark and wood (Hopkins, 1909; Chamberlin, 1918, 1925, 1939; Doane et al., 1936; Keen, 1938; St. George, 1970).
Western Pine Peetle, Dendroctonus brevicomis LeConte
The most important species of Dendroctonus in western North America is D. brevicomis (figure 129). The adults of this species are dark brown to black and 3 to 5 mm long. Adults, eggs, and larvae hibernate in or beneath the bark. Activity begins in the spring when the adults attack trees to start new galleries. The adult galleries of D. brevicomis are easily recognized because they wind about between the bark and wood and crisscross one another. The beetles mine principally in the phloem (figure 128, top), and only slightly engrave the outer sapwood. The larvae feed in the outer bark after completing the first instar. Upon maturing, the adults leave the trees, each through a separate exit hole. Ponderosa (yellow) pine and Coulter pine are the only trees attacked. From 1 to 3 generations are produced each year, depending on latitude and altitude.
Mountain Pine Beetle, Dendroctonus ponderosae Hopkins
This is a very destructive bark beetle. It is 4 to 7.5 mm long, robust, and dark brown to black. It occurs throughout the West, and as far east as western South Dakota, combining the ranges formerly ascribed to both D. ponderosae and D. monticolae Hopkins, which are now considered to be one species.
This beetle attacks principally pondcrosa pines, and occasionally, in very destructive epidemics, any trees with trunks over 6 in. (15 cm) in diameter.
Southern Pine Beetle, Dendroctonus frontalis Zimmerman
This is one of the smaller scolytids, being only 2.2 to 4 mm long. It periodically appears in great numbers in the southern states, and attacks all species of pines, including healthy, vigorous trees of all ages, killing the trees and causing enormous losses.
The Genus Ips
The genus Ips is next to Dendroctonus in importance. These beetles attack mostly pine and spruce, and occasionally fir. They attack primarily young trees and the tops of older ones, while Dendroctonus is more destructive to medium-aged or over-mature trees. The adults are medium-sized, shining reddish brown to black, and cylindrical, easily recognized because of the pronounced concavity on the posterior end, with 3 to 6 pairs of stout spines along its margin.
The principal species of Ips are the California fivespined ips, I. confusus (LeConte), in the West, and the pine engraver, I. pini (Say), in the eastern United States and Canada.
California Fivespined Ips, Ips confusus (LeConte)
This species is very destructive to the tops of mature trees and to young trees, and attacks ponderosa pine, sugar pine, and most other pine species from southern California north to Oregon, west of the Sierra Nevada and Cascades.
The adults are reddish brown to pitch-black, 4 to 4.5 mm long, and have 5 pairs of spines on the margin of the elytral cavity (figure 130). The male makes the "nuptial chamber," and then is joined by 1 to 5 (usually 3) females. Each constructs an egg gallery, and the galleries radiate longitudinally from the central nuptial chamber, with 1 to 5 from each chamber. A gallery typically has 3 branches in the form of a "Y" (figure 128, bottom), mostly in the inner bark and only slightly scoring the outer sapwood. Twenty-five to 50 eggs are laid in each egg gallery. The larvae mine directly away from the main galleries, leaving the mines behind them filled with frass and excrement. Pupation takes place at the ends of the larval mines in cells formed in the inner bark. There are 3 to 5 generations produced during a year.
Ambrosia Species List
- Scolytid Ambrosia Beetles
- Large California Oak Ambrosia Beetle, Monarthrum scutellare (LeConte) (= Pterocyclon)
- Striped Ambrosia Beetle, Trypodendron lineatum (Olivier)
- Western Hemlock Wood Stainer, Gnathotrichus sulcatus (LeConte)
- Lesser Shothole Borer, Xyleborus saxeseni (Ratzeburg)
- Platypodid Ambrosia Beetles
- Wilson's Wideheaded Ambrosia Beetle, Platypus wilsoni (Swaine)
In the family Scolytidae, besides the bark beetles, there are beetles that bore directly into the wood for several inches before constructing lateral brood chambers. They do not feed on wood, but on fungi ("ambrosia") that grow upon the walls of the tunnels. Several generations may continue to extend the galleries as long as the tree retains sufficient moisture for the growth of fungi. The wood along the galleries becomes stained. Although these beetles feed on fungi and may be called "ambrosia beetles," they should be distinguished from the ambrosia-feeding beetles of the family Platypodidae. In either family, the species can also be referred to as "wood stainers." They bore directly into the wood and stain it, the stained areas being black, blue, or brown. The tunnels are made by the adults, and are therefore uniform in size, whereas the tunnels of bark beetles increase in width as the larvae grow. Adult ambrosia beetles feed and care for their young, whereas adult bark beetles do not. Emerging ambrosia beetles leave through the entrance holes that have been made by the mother, whereas each emerging bark beetle excavates its own exit hole.
Scolytid Ambrosia Beetles
Although the scolytid bark beetles are more destructive to trees, one seldom sees their damage to finished lumber, except occasionally in rustic timbers with or without attached bark, as used for building cabins, rustic bridges, and the like. On the other hand, the small holes (about 1.5 mm in diameter) and the stains caused by the ambrosia-feeding scolytid beetles or wood stainers are sometimes seen in finished lumber.
Large California Oak Ambrosia Beetle, Monarthrum scutellare (LeConte) (= Pterocyclon)
An investigation made by Doane and Gilliland (1929) on M. scutellare may be used to illustrate the interesting biology of the ambrosia-feeding scolytids. The adults of this species are 3.5 to 4.1 mm long, elongate, cylindrical, and dark brown. The female, but not the male, has a tuft of long hairs on the margin of the antennal club. It is the male that bores through the outer bark in 6 to 10 hours, producing a tunnel about 1.5 mm in diameter. It takes the male 3 or 4 weeks more to excavate the main gallery and the nuptial chamber in the sapwood. The female then bores out the secondary galleries leading from the nuptial chamber, but the male may assist in the task. There are 2 to 4 of these galleries (figure 131), called "compound ambrosial tunnels," and these vary from 5 to 15 cm in length.
Copulation takes place after the galleries are completed. The female excavates niches along the sides of the secondary galleries into which she deposits her eggs. The eggs are creamy-white and nearly 1 mm long. She may lay as many as 80 eggs, but 51 has been found to be the average number. There are 2 periods of egg-laying, one beginning in March and the other in October. The eggs hatch in 10 to 12 days. The larvae excavate "larval cells," pushing small particles of sawdust and excrement out of the mouth of the cell. The female transfers this accumulation of debris from the secondary galleries to the entrance tunnel, and the male pushes it through the entrance tunnel to the outside. The larvae become full grown in 6 to 8 weeks. Pupation takes place in the larval cells, and requires 8 to 12 days. The pupae are creamy-white, and about 3.7 mm long. There are 2 generations per year.
There is a much smaller species of Monarthrum, M. dentiger (LeConte), only 2 mm long, often found with M. scutellare in live oak (Quercus agrifolia) and white oak (Q. lobata) (Doane et al., 1936).
Striped Ambrosia Beetle, Trypodendron lineatum (Olivier)
This ambrosia beetle is widely distributed in the United States and Canada, attacking nearly all the coniferous genera. The adults (figure 132) are about 3 mm long. The prothorax is subglobose, reddish, with numerous transverse rugosities, the latter being most prominent in the female. The antennae are yellowish brown, with a very large knob, much lighter in color than the other segments. The elytra have several rows of punctures, and are very variable in color, ranging from almost completely black to almost completely yellowish brown, but generally black, with broad, brownish-yellow stripes. They can also be predominantly brownish yellow, with broad, black stripes. In the female, the head is convex and in the male it is concave.
The galleries of T. lineatum penetrate the sapwood and heartwood and often branch considerably. The beetle has been found to be a rather serious pest in recently felled timber. To prevent damage, it is essential that the logs be either moved to the mill as soon as possible or rolled into water, if that is more convenient (Chamberlin, 1939).
Western Hemlock Wood Stainer, Gnathotrichus sulcatus (LeConte)
This species (figure 133) is 3 mm long and blackish brown, with yellow appendages. It is common in the forests of the Pacific Coast and Rocky Mountains, attacking spruce, fir, Douglas fir, hemlock, pine, redwood, and cedar. Characteristics of G. sulcatus and other species of the genus are the long prothorax and the similarity in appearance of the males and females, although the tubercles or teeth at the ends of the elytra of the male are more strongly developed than those of the female, and there are differences in the antennal clubs of the 2 sexes.
The adults make a gallery about 1 mm in diameter to a depth of 5 to 8 cm, and then the gallery branches in a horizontal plane, following annual rings in several directions (figure 134). The fine, white boring dust expelled from the gallery collects in crevices of the bark at the base of the tree. The female lays elongate eggs in niches she has cut both above and below the main gallery - 1 egg in each niche. The larvae extend the niches as they grow (figure 134, right), then pupate in these "cells" or "cradles." There are usually 2 or more broods each year, but they are not regular broods, for all stages of the insect may be found within the galleries at almost any season (Doane et al., 1936). A blue stain (Ceratostomella) develops rapidly in the mines of Gnathotrichus the beetles (Chamberlin, 1939).
Lesser Shothole Borer, Xyleborus saxeseni (Ratzeburg)
This small, cylindrical scolytid is probably the most common species in a genus containing many species of ambrosia beetles. It is common in the forests of Europe and North America, attacking nearly all types of conifers and hardwoods. The females are 2.3 to 3.5 mm long and the males are slightly smaller. The adults are yellow-brown to black, with the elytra obtuse at the apex (figure 135), and with an acute marginal granule on each side. The small, round entrance tunnels lead horizontally to the sapwood and end in a leafshaped cavity in which fungus is grown as food for the larvae (Doane et al., 1936).
Platypodid Ambrosia Beetles
Ambrosia beetles in the family Platypodidae, sometimes called pinhole borers or flatfooted ambrosia beetles, are more slender and elongate than scolytids. They always exceed 3 mm in length, whereas the scolytid ambrosia beetles seldom exceed 3 mm. The platypodids can also be distinguished morphologically from the scolytids because they lack a large spine or projection at the apex of the front tibia that is present in the scolytids. Also, the first tarsal segment is longer than the combined remaining segments, whereas in the scolytids it is shorter (Chamberlin, 1939, 1949). The platypodids are principally tropical beetles, and there is only 1 genus (Platypus) in the United States. The typical differences in the appearances of the 2 groups of ambrosia beetles can be seen in figure 133; scolytid (left) and platypodid.
Wilson's Wideheaded Ambrosia Beetle, Platypus wilsoni (Swaine)
This ambrosia beetle may be used as an example of the few species of Platypus occurring in the United States. It attacks dying, weakened, recently dead, and sometimes healthy trees of all Pacific Coast conifers except cypress. It is a slender, brown, shining beetle, 5.5 mm long, with long, yellow hairs. The female has a more or less blunt posterior end, while the male's elytra diverge and are spined (figure 133). Figure 134 shows the type of gallery mined by Platypus wilsoni, compared with a gallery system mined by the scolytid ambrosia beetle, Gnathotrichus sulcatus just discussed.
Detection of Ambrosia Beetle Damage in Lumber
Both the scolytid and platypodid ambrosia beetles penetrate deeply into the wood, and their tunnels are free of frass. The larvae develop in small cells adjoining the main galleries, and in most species they are fed fungi by the females, which also carry away the larval feces in order to keep the galleries clean. After pupation, the new adults emerge, not by burrowing through the bark like the bark beetles, but by crawling out of the galleries made by the mother.
Each species of ambrosia beetle usually cultivates only 1 species of fungus, and when the females emerge to fly to other trees to excavate new galleries, they carry the conidia (reproductive parts) of this fungus with them. As the fungus develops, it stains the wood blue, black, or dark brown. The depth to which the tunnels penetrate into the wood depends on the beetle species. Four genera have been ranked in order of increasing depth of tunnels, as follows: Xyleborus, Trypodendron, Gnathotrichus, and Platypus (Graham, 1963).
The galleries of ambrosia beetles must be moist to enable the fungus to grow, so neither the fungus nor the beetles can survive in dry or seasoned wood. This is unlike the powderpost beetles, which can not only develop in dry, seasoned wood, but may reinfest the wood members from which the adults emerge, and may infest other hardwood in the building. Ambrosia beetles can sometimes survive in wood that is constantly wet, such as in water tanks or wine casks.
In buildings, ambrosia beetle damage can be observed in either softwoods or hardwoods. In the hardwoods, which can also be infested by powderpost (lyctid) beetles (see under that heading), careful examination of the damage will disclose which insect is involved. The galleries of ambrosia beetles are empty, darkly stained, and intercept milled surfaces at various angles, for the wood was cut after the galleries were excavated by the beetles. Figure 136 shows the typical appearance of framing lumber milled from coniferous trees infested by ambrosia beetles. In this figure, the wires passed through tunnels in the corner of a stud, extending from one surface to the other, give evidence that the stud was milled from an infested tree rather than being infested after it was milled. The wires show that the tunnels are empty and follow a straight course, whereas the tunnels of powderpost (lyctid) beetles are packed with powder and meander about. The wires also show that some of the tunnels were cut at an angle to the surface of the stud. The galleries of powderpost beetles proceed directly into the wood at a right angle to the milled surface, and in any case they would never be found in softwoods. All these are typical signs of earlier ambrosia-beetle infestation that can be seen in some of the framing lumber in almost any residential tract during construction. The author has seen them in framing lumber milled from white fir, Douglas fir, incense cedar, and hemlock, but never to the extent that the tunnels could be said to be sources of significant structural weakness. Live ambrosia beetles are never present. In fact, ambrosia beetles will never be seen in a house unless they emerge from recently cut firewood (Ebeling and Reierson, 1973b).
The discoloration shown in figure 137 was caused by the scolytid Trypodendron lineatum. The figure shows the typical staining caused by ambrosia beetles. In this case, the stain from the fungus was some distance from the tunnels.
Control of Bark Beetles and Ambrosia Beetles on Wood with Bark Attached
Much can be done to prevent infestation of logs, poles, or slabs with bark remaining, as used in the construction of rustic cabins, summer houses, arbors, bridges, and fences. Most bark beetles and ambrosia beetles are not likely to infest such wood when their active season begins if the trees are cut in early fall and dry out or season sufficiently during the winter months. However, some scolytids, such as the redshouldered shothole borer, Xylobiops basilaris (Say), will attack such wood, and further protection may be desired. A solution of 0.5% lindane in a carrier such as deodorized kerosene may be sprayed onto the wood, after which it should be placed in a sunny place to dry. The most effective treatment is pressure impregnation of the wood, which can be done in commercial wood-preserving plants. It is a good idea to check with your state or county agricultural agent or university extension specialist to be sure that the insecticide intended to be used is registered (St. George, 1970).
Note: Nothing can be done about ambrosia beetles after the damaged lumber is in place, for the damage occurs before the tree is cut.
- Woodwasp Species List
- California Species of Woodwasps
Woodwasps (also known as "horntails") cause damage to new structures by defacing finished surfaces as the adults emerge from infested structural lumber. Instances of woodwasp damage are not frequent, but they are very serious matters when they do occur, sometimes resulting in lawsuits involving up to a half million dollars in damage claims in a single building project.
Woodwasps usually come to the attention of the occupants of infested buildings when they see the large holes left by the emerging adults. The cylindrical emergence holes, about 7 mm in diameter, are found in hardwood floors and walls or in their coverings, such as linoleum, carpeting, nonceramic floor tiles, wallboard, or plaster. Woodwasp emergence can occur in any part of the country where the infested lumber is shipped and used. For example, western species of woodwasps emerged in homes in a new housing tract in Wisconsin in such large numbers as to cause "almost an en masse exodus from the housing project" (Frits, 1961).
Description. Woodwasps are large hymenopterous insects, usually 2.5 cm or more in length. The females are much larger than the males, and both sexes vary greatly in size within a single species. Size can be greatly affected by unknown factors in the host-wood species. While siricids are superficially wasplike in appearance, more careful scrutiny will reveal that the thorax and abdomen are uniform in width and closely joined together, while in the true wasps the abdomen is joined to the thorax by means of a narrow petiole. Woodwasps do not bite or sting, and are harmless in this sense. The adults are usually black or metallic dark blue, or with combinations of black, red, and yellow. Tibiae and tarsi are flattened, and the last abdominal sternite ends in a sharp point.
The common name "horntail" is derived from a dorsal hornlike projection called the cornus on the last segment of the abdomen of the female. Originating under the cornus and extending backward is the ovipositor, which in some species may exceed the length of the body (figure 141).
Biology. The biology of the American species of woodwasps has received very little study, but the life history of at least a single Holarctic species, the blue horntail, Sirex cyaneus, was carefully investigated by British workers (Chrystal, 1928; Chrystal and Myers, 1928) and was reported by Middlekauff (1960). There is good reason to believe it is typical of woodwasps in general, at least in essential detail.
Adults fly about in bright sunshine, and make a characteristic noisy buzz. Not many males are seen in collections, but this is probably owing to their habit of remaining in treetops, where mating takes place, whereas the females descend to the lower levels to oviposit (Middlekauff, 1960). Woodwasps are attracted to coniferous trees that are weakened or are dying as a result of fire, disease, insect attack, or other debilitating factors. The species Sirex juvencus californicus was reared in large numbers from ponderosa pine trees in southern California that showed advanced decline caused by photochemical atmospheric pollution (Cameron, 1968). [Bark-beetle infestations have also been associated with atmospheric pollution (smog) injury to pine trees (Stark et al., 1968).]
The female uses her ovipositor to deposit eggs as deeply as 2 cm into the wood of weakened or dying coniferous trees, or she may oviposit in felled trees. Her body may contain 300 to 400 eggs, but she lays only 1 to 7 fusiform, translucent eggs in each oviposition site, spaced at short intervals while withdrawing her ovipositor. The eggs hatch in 3 or 4 weeks, and the larvae then begin to burrow into the wood at right angles to the oviposition channel.
The larva is cylindrical, whitish cream or yellow, slightly S-shaped, and has a small, horny, supra-anal spine on its rear end (figure 138) that is retained through all instars. It has 3 pairs of vestigial thoracic legs, but does not have abdominal prolegs. The larva uses its terminal spine to pack the frass or boring dust in its cylindrical tunnel, and also uses it as a terminal support by driving it into the walls (Chrystal, 1928).
After first tunnellng in the outer sapwood, the developing larva continues toward the heartwood, then returns toward the surface, burrowing in general 25 or 30 cm during its larval life. At intervals, the cast skins from its 3 or 4 molts are incorporated with the frass. Pupation takes place at the end of the tunnel, and requires 5 to 6 weeks. The emerging adult must chew its way through about 2 cm of remaining wood to escape to the outside, leaving a perfectly round exit hole that cannot be distinguished from those of certain cerambycid beetles, e.g., Monochamus oregonensis (LeConte). The minimum period for the complete life cycle is 2 years, but it may be 3 or 4 years or even 5 years in some situations.
Stillwell (1966) stated that Sirex juvencus in New Brunswick usually oviposited (figure 139, A) in 8 to 10 minutes, making oviposition holes 2 to 10 mm long at right angles to the surface, and depositing. 1, 2, and occasionally 3 eggs at intervals in the holes (figure 139, B) while withdrawing her ovipositor. The eggs, which are about 1 mm long, usually overwinter, although some hatch in late summer and the larvae overwinter in the first or second instar (figure 139, C). The larvae molt 5 to 11 times, and pack their cast skins in the frass in the galleries. These galleries vary from 5 to 15 cm long, but are never more than 4 cm from the surface, and pupal chambers (figure 139, D) are normally about 2 cm from the surface.
An interesting aspect of the biology of woodwasps is the symbiotic relationship of the females of the genera Sirex, Urocerus, and Tremex with certain wood-destroying fungi (Francke-Grosmann, 1939; Stillwell, 1966; Morgan, 1968). The adult female becomes infected in the pupal chamber after shedding the pupal skin before emergence (Parkin, 1942). A pair of small, invaginated intersegmental fungal sacs (figure 140, left) project into the body cavity at the basal end of the ovipositor. According to Morgan (1968), woodwasp eggs are always deposited with oidia of a symbiotic fungus and glandular secretions. Stillwell (1966) found fungal oidia (figure 140, right) in the intersegmental sacs of 605 out of 607 Sirex and Urocerus specimens examined, but no oidia could be found in the vestigial intersegmental sacs of 18 specimens of Xeris spectrum. In his experiments, Sirex juvencus did not develop in balsam fir (Abies balsamea) logs that were, not infected with the fungus, Stereum chailletii. Many eggs hatched, but all the larvae died in the first instar. Stereum chailletii is associated with much of the sapwood decay in weakened and newly killed balsam fir in New Brunswick and Nova Scotia, but fruiting bodies have not been found in that area. This suggests that the fungus may be propagated solely by woodwasps in the New Brunswick-Nova Scotia area.
As the woodwasp egg is laid, it becomes infected, and the fungus subsequently penetrates the wood surrounding the larva as it feeds. The larva can live for at least 3 months in a pure culture of the fungus (Middlekauff, 1960). According to Morgan (1968), the larvae do not ingest wood. They secrete a saliva that destroys the fungal mycelium, from which they can then extract the necessary nutrients. The fragments of wood are afterward passed along the outside of their bodies to join the accumulation of frass behind them.
California Species of Woodwasps
There appear to be 12 species of the family Siricidae in California. The subfamily Siricinae contains the genera Sirex, Urocerus, and Xeris. All species have long, filiform antennae that are much longer than the head and thorax combined. The larvae bore in conifers. The subfamily Tremicinae is represented in California by only a single genus, Tremex, in which the antennae are short, slightly swollen in the middle, and at most are as long as the head and thorax combined. The forewings (figure 141, C, top) of Tremex lack vein 2 r-m and possess an appendicular vein (3A); the hindwings (figure 141, C, bottom) lack an anal cell; and the hind tibiae have only a single apical spur. The larvae bore in hardwood trees.
In the adjacent key to the California species of woodwasps of the subfamily Siricinae, keys developed for each of the 3 genera by Middlekauff (1960) and Cameron (1967) have been combined into a single key. The morphological characters iitilized in the key are illustrated in figure 141.
- Females: ovipositor present..........2
Males: ovipositor absent (some species not separable with any degree of certainty)..........12
- Head without pale areas above and behind eyes; cornus of female usually not constricted in middle (except slightly in Sirex longicauda) (figure 141, H); forewing with at least basal half of vein Cu1 present (figure 141, A)..........3
Head with dorsal surface entirely pale or with at least a pale spot behind each eye; cornus of female usually constricted in middle; forewing with vein Cu, usually completely atrophied (figure 141, C)..........7
- Ovipositor as long as the forewing, usually longer (figure 141, H and M)..........4
Ovipositor shorter than forewing (figure 141, I- L)..........5
- Legs with tibiae and tarsi reddish brown; 25-26 antennal segments; wings slightly infuscated (smoky gray-brown, with blackish tinge [Roman sepia]) along veins and around apical margin..........Sirex longicauda
Legs entirely black or blue-black; 20-23 antennal segments; wings completely infuscated..........Sirex areolatus
- Abdomen, except for basal segments, reddish brown; forewing with a transverse fuscous band beneath the stigma and a fuscous apical margin; 2 basal abdominal segments blue- black.........Sirex behrensii
Abdomen entirely bluish black..........6
- Legs, except coxae and trochanters, reddish brown; wings usually nearly hyaline except for infuscated apical margin..........Sirex cyaneus
Legs metallic blue-black, usually with a reddish-brown area in the dorsal portion of each femur; forewing infuscated on apical margin and across middle to uniformly dark violaecous..........Sirex juvencus californicus
- Head lacks a lateral carina behind the eye; ovipositor usually shorter than forewing; hind-wing with a closed anal cell; eye is oval (figure 141, Q) instead of nearly round; hind tibia with 2 apical spurs..........8
Head with distinctive carina (figure 141, B); hindwing without closed anal cell; hind tibia with 1 apical spur; eye nearly round; all species with a white spot behind the eye..........10
- Abdomen black, with segments VII and VIII, and sometimes II, yellow...........Urocerus gigas flavicornis
Abdomen usually entirely black or blue-black..........9
- Wings golden yellow; flagellum of antennae and basal half of tibiae and metatarsi golden yellow; a large light-colored spot behind the eye..........Urocerus californicus
Wings infuscated, brown; most of flagellum, a spot behind eyes, sometimes lateral spots on the abdomen, and the bases of the tibiae and basitarsi white..........Urocerus albicornis
- Cornus not constricted in middle or only slightly so (figure 141, N); tibiae and tarsi usually considerably lighter than femora; antennae basically darker than apical part of flagellum..........Xeris tarsalia
Cornus distinctly constricted in middle (figure 141, 0); legs mostly uniformly reddish..........11
- Abdomen entirely black..........Xeris spectrum
Abdomen, except for first segment, reddish..........Xeris morrisoni
- Forewing with at least basal half of vein Cu1 present..........13
Forewing with Cu1 usually completely atrophied..........17
- Head, thorax, antennae, basal, and apical abdominal segments metallic blue-black; abdominal segments III-VII yellowish orange or reddish brown..........14
Head, thorax, antennae, and basal and apical abdominal segments black, blue-black, or metallic greenish black; antennae blue-black, or basally reddish brown or yellowish orange; abdomen reddish brown posteriad from segment III or IV..........15
- Femora, tibiae, and tarsi of fore- and midlegs and the last 2 tarsal segments of posterior legs reddish brown; apex of fore- and hindwings with distinct infuscated band..........Sirex longicauda
Legs metallic blue-black; abdominal segments III-VII yellowish orange; only slight infuscation in apices of wings..........Sirex areolatus
- Fore- and midlegs beyond the trochanters reddish brown; posterior legs bluish black except distal segment of the trochanter; basal segments of antennae reddish brown or black; thorax metallic blue or greenish; wings slightly yellow, with faint, smoky band around the margins..........Sirex cyaneus
Legs not as above; basal segments of antennae reddish brown or yellowish orange; wings hyaline..........16
- An indistinct, postocular area reddish brown;coxae dark reddish brown; basal segments of abdomen almost black, remainder of abdomen orangish brown; mid-dorsal suture on first abdominal tergite not distinct; hairs on first and second abdominal tergites quite as dense as on dorsum of the thorax; first submarginal cell of forewing not noticeably yellow..........Sirex behrensii
Head unicolorous; coxae and basal segments of the abdomen metallic greenish black; remainder of legs and abdomen reddish brown, rather shiny; mid-dorsal suture on first abdominal tergite usually quite distinct, often slightly opened for part or all its length; density of hairs on first and second abdominal tergites, especially medially, not as great as on dorsum of thorax; costal and first submarginal cell of forewing noticeably golden yellow..........Sirex juvencus californicus
- Head lacks a lateral carina; hindwing with a closed anal cell; eye is oval instead of nearly round; hind tibia with 2 apical spurs..........18
Head with distinctive carina behind the eye; hindwing without closed anal cell; hind tibia with 1 apical spur; eye nearly round; all species with a white spot behind the eye. (Male siricids are normally smaller than females, and the last abdominal sternite ends in a sharp point.)..........20
- Abdomen reddish brown; wings golden yellow; legs and antennae reddish brown..........Urocerus californicus
Abdomen with segments III to VI yellow, the remainder black; wings nearly hyaline..........19
- Hind basitarsus 4.1 to 5.6 times longer than broad..........Urocerus albicornis
Hind basitarsus 6.4 to 8.1 times longer than broad..........Urocerus gigas flavicornis
- Abdomen black..........Xeris spectrum
Abdomen almost reddish..........21
- Postocellar area very rugose; median furrow shallow, broadly rugose (figure 141, E)..........Xeris tarsalis
Postocellar area sparsely pitted, not rugose, polished, a distinct, narrowly rugose median furrow (figure 141, G)..........Xeris morrisoni
The Genus Sirex
Six of the 9 species of Sirex that occur in North America can be found in California. The females oviposit in the trunks of many species of native conifers in the genera Abies, Cupressus, Larix, Libocedrus, Picea, Pinus, Pseudotsuga, and Sequoia. Members of this genus (except for S. behrensii) do not have the pale area behind the eyes such as that possessed by Urocerus and Xeris. The cornus is not normally constricted (figure 141, H-M), and the forewing (figure 141, A) has at least the basal half of Cu1 present.
Sirex longicauda Middlekauff (figure 138) appears to be confined to California. It is one of the species commonly found infesting houses (Ebeling and Wagner, 1963). These insects are metallic dark blue, except that the males, first recognized and described by Middlekauff 1962), are reddish brown on abdominal segments III-VII and the tibiae and tarsi of the first 2 pairs of legs. The females are usually about 4 cm long, and the males are slightly over 2.5 cm.
Sirex areolatus (Cresson) ranges throughout the Pacific Coast states, as well as Arizona, New Mexico, and Colorado. It is predominantly coastal in distribution in California. Like S. longicauda, the female of this species has a steel-blue body, but her legs are bluish black throughout, whereas the legs of S. longicauda have red tibiae and tarsi. The 2 species are about equal in size. The male of S. areolatus can be separated from S. longlicauda by the entirely blue-black tibiae and tarsi. Females of S. longicauda and S. areolatus have a much longer ovipositor than other species of Sirex (figure 141, H and M).
Sirex behrensii (Cresson) occurs in the Pacific Coast states and Nevada. The females can be distinguished by the reddish-brown abdomen beyond the second segment (figure 142) and by the shape of the cornus (figure 141, L). The males have a reddish abdomen except for the basal segments; the first 2 pairs of legs are reddish brown except for their coxae and trochanters; and the basal segments of the antennae are red. The legs of S. behrensii are colored similarly to those of S. longicauda, but the bases of the antennae, an indefinite area behind the eyes, and the apex of the abdomen are reddish brown.
Sirex juvencus callifornicus (Ashmead) ranges throughout the Pacific Coast states, and has also been recorded from New Mexico. The body and appendages of the female are dark blue and the ovipositor is short, extending only 2 to 3 mm beyond the tip of the cornus (figure 141, K). The wings have a smoky band around the apical margin, and also one across the wings beneath the stigma. The male of this species was not described until 1967 (Cameron, 1967). The distal segments of the antennae, head, thorax, abdominal segments I and II, a triangular area on the anterior dorsum of segment III, and the coxae are metallic greenish black. 'The basasl 5 or 6 segments of the antennae, the remainder of the abdomen, and the legs are reddish brown
The blue horntail, Sirex cyaneus F. (plate II, 2), is generally believed to have originated in North America, where it may be found in most of the continent north of Mexico. This species is among those with an ovipositor shorter than the forewing. Its abdomen is entirely bluish black, and its legs, except for coxae and trochanters, are reddish brown. The wings are nearly transparent except for a smoky gray-brown apical margin. The cornus is not shouldered (figure 141, J). The wings of the males differ from those of the females in being slightly yellow, with a faint smoky band around the margins. The last pair of legs of the male are bluish black, in contrast to the reddish-brown legs of the females. The bases of the antennae are reddish brown or black.
The Genus Urocerus
Three of the 5 species of Urocerus that occur in North America may be found in California. Urocerus contains our largest species, attaining in U. californicus a length of nearly 4 cm from head to tip of cornus. The females oviposit in the trunks of conifers in the genera Abies, Larix, Libocedrus, Picea, Pinus, Pseudotsuga, Thuja, and Tsuga.
In common with Xeris, species of Urocerus possess a distinctive pale spot behind the eye, a constricted cornus, and usually vein Cu1 in the forewing is completely absent. Unlike Xeris, the head lacks a lateral carina, the ovipositor is usually shorter than the forewing, the hindwing has a closed anal cell, the eye is oval (figure 141, Q) instead of round; hind tibae have 2 apical spurs.
Urocerus californicus Norton is the largest and possibly the most common western woodwasp (Middlekauff, 1960). The female may reach 4 cm in length. It is the only California siricid with the combination of a black abdomen and golden yellow wings and antennae. It attacks principally the firs (white and red firs and balsam), species not commonly used in construction, and is therefore not likely to be found as a pest in buildings. The abdomen of the male is reddish brown.
Urocerus albicornis (F.) is relatively uncommon in California. In this species and in the female of U. californicus, the abdomen is almost entirely black. However, the wings are smoky brown, in contrast to the golden yellow of the wings of U. californicus females. In the male, abdominal segments III to VI are yellow and the remainder are black. The wings are nearly transparent. Belyea (1952) (cf. Middlekauff, 1960) stated that the life cycle from egg to adult required 2 years, but other authors state that it may be completed in 1 year. The larval burrows are said to run in all directions, and to be closely packed with a very fine, dustlike frass.
Urocerus gigas flavicornis (F.) ranges throughout the coniferous belt of North America, in the Pacific Coast states, and south along the Rocky Mountains to Arizona and New Mexico. It is somewhat smaller than U. californicus, and abdominal segments VII, VIII, and sometimes II are yellow
The Genus Xeris
There are only 4 known species of Xeris, 3 in North America and 1 confined to the Himalayas. Like Uroceus, the species of Xeris have a pale spot behind the eye, but the ovipositor is longer than the forewing. The hind tibia has 1 apical spur. The eyes are more nearly round (figure 141, P) instead of oval, as in Urocerus.
The female of Xeris tarsalis (Cresson) (= macgillivrayi Bradley) can be distinguished from the other 2 species of American Xeris by the unconstricted cornus, the tibiae and tarsi being considerably lighter in color than the femora, and the basal part of the antennae being darker than the apical part of the flagellum.
Xeris morrisoni (Cresson) is widely distributed in the mountains of California, but attacks mostly fir and lodgepole pine, and is not likely to be found in commercial lumber. It can be distinguished from X. spectrum by the reddish abdomen.
Xeris spectrum (L.) is Holarctic in coniferous forests, extending farther south in mountainous regions. Lodgepole pine is believed to be its favorite host in California. This species may be distinguished from X. morrisoni by its entirely black abdomen, in contrast to the reddish abdomen of the latter.
The Genus Tremex The species of Tremex can be separated from other siricids by the short antennae. Only a single species with several color phases has been described from North America. Unlike other siricids, species of Tremex feed on weakened or dying deciduous trees, not on conifers.
Tremex columba (L.) (the pigeon tremex) is widely distributed over the United States, occurs in southern California, and has been reared from many species and varieties of deciduous trees. In the typical T. columba, most commonly found in the northeastern United States and southeastern Canada, the abdomen is black, with ocher-yellow bands and spots along the sides. The common form in Colorado, New Mexico, Arizona, and California is the race aureus, in which the ground color of the abdomen is yellow and the markings are black. The wings are golden yellow. The race sericeus may be found in the southeastern United States, as far north as Pennsylvania and west into Colorado, New Mexico, Arizona, and California. The entire body is fulvous (tawny), the legs distal to the femora are yellow, and the wings are dark reddish brown. More study will be required to determine whether these 2 color forms should be given subspecies status (Middlekauff, 1960).
In New Brunswick, the female of T. columba deposits her eggs most commonly in weakened or injured beech trees from about the middle of August to the middle of October, laying 2 to 5 eggs in each oviposition hole. The blackish eggs may either hatch in 2 to 4 weeks or the next May or early June. The larvae may be 4 cm long, and are believed to be able to complete their growth and transform to pupae within a year. Usually, only the upper trunks and injured branches in the crown of the tree are attacked, and this species is therefore of little economic importance (Stillwell, 1967).
One of the most important factors contributing to woodwasp damage is forest fire. In the western states, where there is characteristically a long dry season in summer, severe infestations of woodwasps frequently occur in the wakes of fires that annually kill or damage thousands of acres of timber. Fire-killed timber is salvaged and utilized for certain construction purposes, as for example the studs and subflooring. Although kiln-drying will kill woodwasp larvae that have survived milling operations, the relatively low value of the lumber makes this treatment economically impractical.
There is danger of increasing the range of distribution of the various species through commerce. Pacific Coast species have been reported emerging from a new door in Massachusetts and from framing of a new house in Georgia. Australia requires that raw lumber imported for use in crates or prefabricated housing be heated by a steaming treatment at 165 °F (74 °C) for 10 hours to kill such insect pests (NPCA, 1964a).
Woodwasps, as well as certain wood-infesting beetles, are "built in" to the house at the time of construction, and whatever damage they do will be completed within the first 2 or 3 years after the house is built. The exit holes, although conspicuous because of their large size, are not likely to be numerous, although there have been occasional instances of dozens of holes in one building. However, the damage from woodwasps is not the structural weakening of timbers, but the defacement of walls, floors, and other interior surfaces from which the adults emerge.
The exit holes of adult woodwasps are not necessarily found in the lumber originally infested, but in whatever material the adult insects must penetrate in their attempts to leave infested wood and fly away. The adults have powerful jaws and are said to be able to cut through lead sheathing (H. Scott, 1932; Middlekauff, 1960). In one industrial building, a woodwasp had bored through 2.5 cm of plaster.
Some homeowners have reported a small amount of "sawdust" around or under the exit holes of the emerging adults, but most have not observed this. R. W. Stark (correspondence) found no frass around or under holes of woodwasps emerging from fir logs. This was in contrast to the exit holes of the newhouse borer, Arhopalus productus, a cerambycid beetle that pushes out long drillings that look like cigarette tobacco from its burrow when emerging.
Neither woodwasps nor newhouse borers can reinfest buildings. This is in contrast to the oldhouse borer, Hylotrupes bajulus, another cerambycid that may attack very old buildings and can reinfest the same structural timber until the wood is reduced to a mass of powder. The oldhouse borer also makes holes about 7 mm in diameter, but it appears to be confined to the east coast and Gulf states
Control of Woodwasps
Woodwasp adults can emerge from wood that has been sprayed or brushed with the commonly available insecticides. However, the emergence holes can be filled with any appropriate filler material, and the filled area can be spot-painted. A painted wall can be redone, of course, but it is impossible to be certain that the last adults have emerged until about 3 years after the house is constructed.
Kiln-drying or vacuum fumigation of the lumber before use would be effective, but merely fumigating it in boxcars or under a tarpaulin has not proved to be of much value (Middlekauff, 1962). Fumigation has likewise proved to be ineffective in buildings (Ebeling, 1968). After some failures with methyl bromide, in one building Vikane (sulfuryl fluoride) gas was used in order to obtain a maximum degree of penetration. It was used at a dosage of 2 lb per 1,000 cu ft (0.91 kg per 28 cu m) with a 48-hour exposure. For the first 30 days after fumigation, emergence of woodwasp adults had ceased, whereas it continued during this period in nearby nonfumigated buildings in the residential tract. However, after the approximately 30-day period, emergence of adult woodwasps was again observed. The author concluded that the gas penetrated to and killed woodwasps that were near the surface, either because they were in the act of emerging or because the lumber had been cut to within a short distance from their burrows. Evidently, many of the insects were not reached by the gas and later emerged (Ebeling, 1968).
As already stated, woodwasp larvae burrow deeply. Even the pupal chambers are 2 cm or more from the surface. Some of the larvae or pupae are likely to be left at considerable distances from the surface in such wooden members of residential construction as studs and floor and ceiling plates. Although the tunnels may be exposed when such lumber is cut in the sawmill, they are tightly blocked with frass and borings by the larvae, and this may prevent the passage of lethal amounts of even the most penetrating fumigants. In Britain, however, timbers up to 10 cm thick are reported to have been successfully fumigated to control woodwasps by using 3 lb per 1,000 cu ft (1.36 kg per 28 cu m) of methyl bromide, applied for 24 hours at not less than 90 °F (32 °C) (NPCA, 1964a).
One pest control operator observed that of the 54 holes made in the plaster walls of 4 houses by emerging woodwasps, none were made in the areas at which the plaster was contiguous to studs. He was able to push a wire probe through each hole and move it about freely within the interstud wall voids. The woodwasps had emerged from the sides of the studs, entered the interstud wall voids, and then bored their way through the plaster. The silica aerogel Dri-die 67® was blown into the walls at the rate of 6 grams per interstud space (3 g below and 3 g above each fire block) through holes drilled into the plaster walls and subsequently filled with matching plaster.
The number of emergence holes in the treated houses had steadily increased up to the date of treatment, but no new holes were found thereafter. Since the treated houses were only 6 months or less old, and emergence could continue for 2 or 3 years after construction, it was unlikely that the cessation of emergence immediately after treatment was a coincidence. Dusting of this kind can be done most efficiently with a slightly modified water-type fire-extinguisher, large numbers of which are currently being sold to pest control operators for applying insecticide dusts into wall voids, attics, and other enclosed spaces. (See under "Residual Protection" earlier in this chapter.) The 6 grams of Dri-die used per interstud space amounted to 2 lb per 100 linear ft (0.91 kg per 30 m) of wall, or 2.5 lb per 1,000 sq ft (1.14 kg per 93 sq m) of floor space.
The reason that a dust desiccant was recommended was that, being inorganic, it would remain effective against woodwasps as long as needed, and also serve as a preventive against drywood termites, cockroaches, silverfish, carpenter ants, odorous house ants, fungus beetles (Lathridiidae), tropical rat mites, and other cryptobiotic pests.
The pest control operator responsible for the successful treatment just described had subsequent successes with the same method. However, the author was informed by R. E. Wagner that he had observed woodwasp emergence holes in a house at the point of contact of plaster and stud. In that event, the emerging insects would probably not have had contact with dust if the wall voids had been treated. Even in such a situation, the dust desiccant in interstud spaces might be expected to kill most of the woodwasps.
- Carpenter Ant Species List
- Some California Carpenter Ants
- Camponotus nearcticus Emery
- Camponotus hyatti Henry
- Camponotus clarithorax Emery
- Camponotus vicinus Mayr
- Camponotus semitestaceus Emery
- Camponotus laevigatus (F. Smith)
- Camponotus modoc Wheeler
- Some Eastern Species
- Some California Carpenter Ants
- Control of Carpenter Ants
General information on the biology of ants may be found in chapter 6. In the present chapter, only those species that damage wooden structures will be discussed. They are called "carpenter ants," and are all included in the genus Camponotus. Besides causing considerable destruction to structural timbers, carpenter ants are also nuisances in the same way as any other ants, that is, by crawling about in the house in search of food. They are distributed throughout the United States, and occur at elevations up to 9,000 ft (2,700 m). They are abundant in forests, and can be easily found under the loose bark of dead trees, stumps, or fallen logs.
In the Pacific Northwest and some other areas, carpenter ants are considered to be equal to termites in importance as pests. They often infest cabins in forests. In cities, they usually infest houses in foothill areas containing native chaparral or trees or in estates containing large shade trees, but are sometimes found in homes in crowded residential districts as well.
These ants are predominantly black, and are among the largest species in the United States. The petiole has a single node. They are polymorphic; there are workers of different sizes, called "major," "minor," and "intermediate." These workers can emit a strong formic acid odor. They do not sting, but their bite can be painful, particularly if they inject formic acid into the wound.
Among American carpenter ants, the species for which the biology has been most thoroughly investigated is the black carpenter ant, Camponotus pennsylvanicus (De Geer). It is especially common in the eastern and central United States up to 5,500 ft (1,700 m) elevation. In a study of colonies made on the campus of the University of Illinois, Pricer (1908) concluded that sexually perfect individuals are not produced in a colony until it contains approximately 2,000 workers, and that a period of 3 to 6 years or longer is required for a colony to reach this size. The distributions of castes in the 2 largest nests found by Pricer were as follows: In an oak log, he found 3,018 workers, 1 wingless queen which started the colony, 196 winged queens, 177 males, and 842 larvae. In an ash tree, he found 3,212 workers, 1 wingless queen, 233 winged queens, 176 males, and 724 larvae. In his studies, he found 14 colonies with 1,000 or more workers. The smallest colony among the 24 Pricer found consisted of 1 wingless queen, 106 workers, and 93 larvae. Colonies did not produce winged forms until they were more than 2 years old. The winged forms that were produced in summer overwintered in the parental nest, and left for the nuptial flight in May to late July.
Among ants reared in 2 artificial nests in the laboratory at temperatures ranging from 70 to 90 °F (21 to 32 °C), Pricer found that C. pennsylvanicus spent the following numbers of days in the various stages: egg, 24; larva, 21; and pupa, 21 - a total of 66 days from egg to adult.
Carpenter ants barrow into wood not to feed on it, but to make nests, In nature, their nests are found in dead trunks of standing trees, stumps, or logs, or under fallen logs and stones, sometimes in galleries extending far underground. They also burrow into structural timbers, and if their galleries are extensive, the ants can cause some damage to buildings. Even species able to burrow into sound timbers prefer to burrow into unsound wood, such as that which has been invaded by dry rot. More commonly, at least in California, they use existing hollow spaces, including wall voids, hollow doors, cracks, crevices, furniture, and termite galleries, in which to make their nests. In forested areas, they often establish colonies in masses of fir needles and other refuse that they accumulate within walls, under floors, in attics, and in other undisturbed areas.
The nest may also be behind the rear end of a drawer in a dresser or cabinet, or behind books in a library. In an area that is seldom disturbed, such as an attic, the nest may be exposed to view, as on the plaster laths between 2 ceiling joists.
Carpenter ants sometimes enter a house at a point at which tree branches contact the roof or other parts of the house. They may also enter through such access points as windows, holes in the foundation, foundation vents, heating ducts and air-conditioners, or along power or telephone lines. They can also be brought into the house in firewood.
Signs of carpenter ant infestation are the large, black ants running about the house or swarms of the winged reproductives in or on the house, usually in the spring; piles of fibrous, sawdustlike borings which the ants have expelled through slitlike openings in the infested wood; the slit-like openings themselves in woodwork, especially in window or door casings; or a faint rustling in walls, floors, and woodwork (Furniss and Every, 1958).
The borings of carpenter ants are similar to those of carpenter bees. The borings of these 2 hymenopterous wood invaders and the fecal pellets of the drywood termite, Incisitermes minor, are shown in figure 143. The sizes of the particles can be visualized by the fact that the fecal pellets of drywood termites average about 0.85 mm in length.
A carpenter ant colony in a home may consist of the progeny of a single queen that has invaded the house. It is more likely to consist of individuals that immigrated from an existing colony, especially when the colony is seriously disturbed, as in the clearing of building sites. Or, the ants may have merely wandered in from the outside in search of dead insects, other animal matter, or sweets.
In a survey, 30 American and Canadian pest control operators were asked where they found carpenter ants nesting in houses. Their answers indicated the relative importance of the different locations: inside walls (15), in ceilings (10), under outdoor siding (7), in wood contacting soil near foundations (7), by downspouts near tile roof (6), around roof gutter braces (5), under roofing panels (4), in hollow doors (4), in floors (2), in windowsills (2), under a bathroom floor (1), and in padded ceiling insulation (1) (Anonymous, 1967a).
All kinds of houses are invaded by carpenter ants, regardless of age or type of construction. When they infest wood, some preference is shown for moist, rotting timbers about the foundations, but sound wood can be mined by some species, anywhere in a house. Carpenter ants excavate galleries that somewhat resemble the work of drywood termites, but they contain no debris and have an almost polished appearance. The galleries extend in all directions, like those of the drywood termites and unlike those of the subterranean termite, which follow the spring growth.
The workers may sometimes be seen in the house, foraging about for food, or swarms of the large winged reproductives may emerge from the colony and try to escape through the windows. With either the wingless or winged forms, it is important to know how to distinguish them from termites (figure 66), for control methods differ. The winged forms comprise only a part of the colony - the rest stay behind and continue to develop and extend the infestation.
Some California Carpenter Ants
There are so many species of carpenter ants throughout the United States that either occasionally invade homes foraging for food or, in the case of some species, build their nests within houses, that space would not permit a discussion of all species, even if adequate information were available, which in many areas is not the case. Therefore, the following discussion is confined to the house-infesting carpenter ants of California, although some of the species may be found in other western states and even in the East.
Camponotus nearcticus Emery
This species (figure 144, A) has a discontinuous distribution, occurring in the West from British Columbia to California, thence eastward to Idaho. Farther east, it is found from North Dakota to Ontario, and ranges from Colorado to Florida. These ants occur mostly at lower elevations, but have been observed at altitudes as high as 6,000 ft (1,800 m). The workers are 4.5 to 7.5 mm long, smaller than those of most carpenter ants. The color is generally black throughout, but on some specimens, some segments or areas of the body may be largely reddish or brownish. The body is shiny, particularly the abdomen. This species forms small colonies of less than a hundred to several hundred, "in dead twigs and branches of trees, in or beneath the bark of dead or live trees, in insect galls, pine cones, beneath the bark of logs and stamps, in hollow stems of plants, and in wooden posts." Day and night, the workers crawl over shrubs and trees in search of honeydew and dead insects. They often form their nests in houses, but seldom infest household foods (M. R. Smith, 1965).
Camponotus hyatti Henry
This species (figure 144, B) is similar to C. nearcticus in size and appearance, but is restricted to southern California, where it normally nests in dead limbs of oak. In the chaparral belt, where so many suburban homes are being built, it is often found in them, searching for sweet foods. These ants may sometimes infest termite galleries in buildings (R. R. Snelling, correspondence).
Camponotus clarithorax Emery
This is the species (figure 144, C) most commonly found in houses in southern California, and it ranges northward to Oregon. The ants nest in crevices, in interstud wall voids, or under floors between joists, in hollow door panels and window casements, and in termite galleries. If "sawdust" (figure 143) is found that has been pushed out of the structural timbers by this species, it is most likely to be from wood that has been softened by dryrot fungus infection. These ants feed largely on' carbohydrates. Camponotus clarithorax is a small species; major workers are 7 to 8 mm and minor workers are 5 to 6 mm long. The head and gaster are dark brownigh to nearly black, and the thorax is yellowish to reddish. The anterior margin of the clypeus has a notch in the middle (as in C. hyatti), and the cheeks have coarse punctures, from each of which arises a short, stiff hair (R. R. Snelling, correspondence).
Camponotus vicinus Mayr
These carpenter ants (plate II, 3; figure 144, D) are widely distributed throughout California in both lowlands and mountains, and may be found under stones in rather dry, sunny places. The ants are large, the workers being 6 to 10 mm, winged males 10 mm, and the queens 13 to 15 mm long. They have a red thorax and black abdomen. The life cycle requires about 2 months, And approximately 2 years will pass before a new colony will begin to produce alates. This species may have large colonies, with over 3,000 individuals. They do not nest in houses, but may sometimes be seen in them, foraging for food. Their nests are usually in the soil at some distance from any house. They occasionally damage lawns by building their mounds in them.
Camponotus semitestaceus Emery
This species (plate II, 4; figure 144, E) differs from C. vicinus in being paler, with the thorax and first and second segments of the abdomen near the petiole yellowish. Its habits are similar to those of C. vicinus.
Camponotus laevigatus (F. Smith)
This species (figure 144, F) ranges from Colorado westward, most often in the Transition Zone. This diurnal forager is common throughout California at high altitudes, and its large colonies may be found in dry stamps or logs. It seldom invades houses. The entire insect is jet black and very shiny, with abundant white hairs, and often with strong, bluish reflections. It can burrow into sound wood, and has some potential as a structural pest, but generally utilizes galleries of dampwood termites (R. R. Snelling, correspondence).
Camponotus modoc Wheeler
The workers of C. modoc are 5 to 11 mm or more in length, dull black with reddish legs, with a lighter color on the margins of the segments of the gaster. The abdomen is covered with closely appressed, long, golden hairs (R. R. Snelling, correspondence). This species is most common in the northern part of California at altitudes beginning at 3,000 ft (900 m). It is occasionally found at lower elevations, even in the valleys. It can mine sound wood. Large colonies occur in stumps and rotten centers of fir-tree butts, doing little damage to living tissue. These ants sometimes work from near-by stumps into the timbers of cabins or larger houses. This species is pugnacious, and bites viciously when disturbed (Mallis, 1941 a).
The black carpenter ant, Camponotus pennsylvanicus (De Geer), is the most common species in the eastern states. The red and Florida carpenter ants, C. ferrugincus (F.) and C. abdominalis floridanus (Buckley), are also common.
Control of Carpenter Ants
The control of these ants may involve the destruction of colonies within 90 m or so of the house, around the foundation where ants are observed, or even under the house, using 20% chlordane spray or 50% dust, or lindane at lower concentrations. Use enough spray or dust to cover all surfaces on which the ants may crawl. Provided the location of the nest can be determined, 6% chlordane dust in wall voids or other hard-to- reach places inaccessible to liquids has been recommended (Rachesky, 1970a).
Inside the house, carpenter ants may be found in secluded but not completely covered places. These can be easily treated. It may be necessary to remove siding, window casings, doorsills, or similar members to reach the ant runways. If the ants are within timbers, try to determine where their galleries are by locating the small, slitlike openings or the piles of "sawdust," then bore small holes into the timbers to reach the galleries, and blow 5% chlordane dust into them (Furniss and Every, 1958). Drione®, a formulation of Dri-die 67® and pyrethrins, is also effective for treating carpenter ant nests, and results in rapid knockdown and kill. The most difficult part of carpenter ant control is often the location of the nest. A doctor's stethoscope is helpful in locating nests in particularly difficult cases.
A pest control operator in southern California has successfully controlled carpenter ants in wall voids by blowing the fluorinated silica aerogel, Dri-die 67. The dust retains its insecticidal properties indefinitely if it does not become wet, and therefore acts as a preventive against possible future infestations of carpenter ants as well as other species of cryptobiotic insects.
CARPENTER BEES (ANTHOPHORIDAE)
- Carpenter Bee Species List
- California Species of Xylocopa
- Mountain Carpenter Bee, Xylocopa tabaniformis orpifex Smith
- Valley Carpenter Bee, Xylocopa brasilianorum varipuncta Patton
- California Carpenter Bee, Xylocopa californica californica Cresson
- California Species of Xylocopa
- Economic Importance
- Control of Carpenter Bees
There are 2 groups of Hymenoptera whose activities in dead wood and wooden structures have suggested the term "carpenter" in their common names: carpenter ants and carpenter bees. Carpenter ants burrow into wood, expelling typical borings (figure 143), or use ready-made enclosed spaces, not only to make nests in which to lay eggs and care for their young, but also as harborages for themselves. They leave the gallery system, which is sometimes very extensive, to forage for food, but always return to their "home." Carpenter bees likewise burrow into wood, forming a series of chambers,but only to rear their offspring. The chambers, beginning with that farthest from the entrance, are each provisioned with a pollen mass on which a single egg is laid, and are then capped with disks of wood particles. Each pollen mass in the series of burrows is enough to bring a larva to maturity. After scaling the cell nearest the burrow entrance, the adult carpenter bee departs, not to return. After the burrows are abandoned, other carpenter bees may find them and store pollen in them to feed on before hibernation. (They use old carpenter bee tunnels for this purpose.)
Identification. In North America, the wood-boring or carpenter bees are found in 2 genera, Ceratina and Xylocopa. The former includes the "little carpenter bees," which average about 6 mm in length, are rather slender, and metallic green, blue, purple, or rarely black. They occasionally nest in hollow stems and reeds, but most often in the hollowed-out stems and canes of pithy plants (H. S. Smith, 1907). Their habits are similar to those of Xylocopa, but they do not bore into structural timbers, and are usually of little importance to the homeowner.
The genus Xylocopa includes the large, robust carpenter bees that somewhat resemble bumble bees, except that the dorsal surface of the abdomen is largely naked, whereas that of the bumble bee is hairy. Also, the females have a dense brush of hairs on the hind legs, as contrasted with the pollen baskets of the bumble bees. Carpenter bees are usually metallic blue-black, with green or purplish reflections, but in some species the males are entirely or partially buff or pale yellow. Other morphological differences between the sexes are: males have 13-jointed antennae, females have 12 joints; males have 1 spine at the tip of the hind tibia, females have 2; males have 7 exposed abdominal segments, females have 6; males have only 2 teeth at the apex of the mandible, females have 2 at the apex and also on the upper margin. The triangular row of spines on the dorsum of the last abdominal segment of the females is not present on the males (Essig, 1926). Keys and detailed descriptions of the genera, subgenera, and species of the New World and Old World large carpenter bees (tribe Xylocopini) were prepared by Hurd and Moure (1963). Keys to California Xylocopa were prepared by Hurd (1955).
Biology. The biology of Xylocopa virginica virginica (L.) has been described in considerable detail (Rail, 1933; Osmun, 1954; Chandler, 1958). This species ranges from Maine to Florida and westward to Nebraska and Texas. It is black in both sexes, marked with areas of yellow hair. The adults of both sexes hibernate in abandoned nest tunnels, as just mentioned. In areas of low winter temperatures, many may die. In the spring, the survivors emerge from the tunnels to search for nectar for their own food. Mating then takes place, and extends into the nest-construction period. For the purpose of preparing her nest, the female may use an old gallery without further burrowing, or she may lengthen it, or may bore an entirely new gallery or extend one from an entrance used by several bees.
Newly excavated galleries average 10 to 15 cm in length, but a gallery system developed by several bees may be 2 to 3 m in length. A mass of pollen and regurgitated nectar is packed into the bottom or end of the brood gallery, and the female lays an egg on it. She then seals off this portion of the gallery with a disk of chewed wood pulp. This procedure is repeated until a linear series of an average of six cells is formed. The developmental period for X. v. virginica is 36 days. Following emergence, the adult bee spends a day or two within the cell in drying and cleansing itself, and perhaps feeding on pollen remains.
Rau (1933) found that with X. v. virginica, the first bee to become an adult developed in the first cell to be provisioned. It then cut through all the partitions, by-passing the other developing brood. The newly emerged carpenter bees have different habits from their parents, that have died by the time the young emerge. They store caches of pollen in abandoned carpenter bee tunnels. The pollen is consumed during inclement weather by bees that are about to hibernate. During this period, there is no mating and no boring in wood, except that an occasional bee may enlarge its hibernating quarters.
Nininger (1916) studied the biology of X. tabaniformis orpifex nesting in a small, deserted cabin in the San Gabriel Mountains in southern California. The insects preferred sound redwood, but a few bored into sound Douglas fir. The bee and its typical cells are shown in plate II, 7, and figure 145. Slanting or horizontal surfaces were generally chosen by the bees studied by Nininger, and entrances were made from the undersides of the timbers. The burrow continued a short distance at (or nearly at) right angles to the surface, and then turned sharply to follow the grain of the wood. The burrows varied in length from 2.5 to 30 cm (average 10 to 15). Burrows of greater length were believed to be more than one season's work. A female could lengthen her burrow by 2.5 cm in six days. In their tunneling, the females nearly always remained equidistance from the 2 outer surfaces of a timer, possibly guided by the vibration caused by the burrowing activity.
When a new site was chosen by a single female, others soon found it, and every available timber became honeycombed with tunnels. The bees did not store food for themselves in the tunnel, ]but came forth in search of food when temperatures were 20 to 21 °C, (68 to 70 °F) or over. The provisioning of the cell and oviposition were approximately as described for X. v. virginica. There were usually 5 or 6 cells completed - about 1 per day.
Developmental periods for X. t. orpifex were as follows: The eggs hatched in 7 days. The larvae developed in 22 to 28 days, but remained the next 15 to 19 days with little change. About 40 to 45 days were spent in the pupal stage. Thus, the period from egg to adult ranged from 84 to 99 days. If remnants of larval food were present, the bee might remain for some time within its cell, but otherwise it destroyed the entire series of cell partitions separating it from the tunnel entrance in order to get to the outside. Sometimes the emerging bee waited for the bees in the cells ahead of it to emerge, but this did not appear to be the rule (Nininger, 1916). Davidson (1893) stated that the first adult to emerge came from the last cell to be completed. He stated that males developed in the last cells to be completed, and that they developed more rapidly than the females. Thus, Davidson's observation did not agree with Rau's, mentioned earlier, regarding the order in which the cells were evacuated.
California Species of Xylocopa
In America north of Mexico, there are 7 species of Xylocopa. In the eastern United States is found X. virginica virginica, considered to be the most destructive carpenter bee in the country (Chandler, 1958). Of the 3 species in California, X. tabaniformis orpifex Smith (figure 145) causes most of the structural damage, but damage is occasionally reported from X. tabaniformis androleuca Michener and X. californica arizonensis Cresson (Hurd, 1955, 1958). Nininger (1916) stated that X. brasilianorum varipuncta Patton preferred to burrow in decaying wood, but Mallis (1969) had records of its damage to structural timbers. Likewise, in 1970, Roy J. Pence (personal communication) observed the Hawaiian subspecies around structurally sound picnic tables that had been severely mined by the insect.
Mountain Carpenter Bee, Xylocopa tabaniformis orpifex Smith
This species is 12 to 17 mm long, and both sexes are black (plate II, 7). The head of the male has white and yellow hairs mixed with the black. Mature larvae are yellowish white, robust, and 7 mm long. The details of the life cycle of this species have already been discussed under "Biology" to exemplify the usual life cycles of carpenter bees.
These bees are found mainly in the foothills and mountains of California, Oregon, Nevada, Arizona, and Baja California. Hurd (1955) observed that the creation of suitable nesting sites by man, in the form of structural timbers, had resulted in the extension of the range of this species to lower altitudes.
Valley Carpenter Bee, Xylocopa brasilianorum varipuncta Patton
This bee is 18 to 20 mm long, somewhat larger thanX. t. orpflex. The metallic black of the female, with brilliant violaceous, brassy, or bronzy reflections, is in sharp contrast to the golden-brown or buff color of the male (plate II, 8; figure 146). This is the species that is most likely to be found in the valleys and lower foothills of California, Arizona, and Baja California. It is said to prefer partially decayed live oak, deciduous oak, pepper (Schinus molle), eucalyptus, and other hardwood trees. Several of its burrows may have a common entrance (Nininger, 1916). Figure 147 shows a male bee emerging from a tunnel that had been cut into the exposed transverse section of the sawed-off flowering stalk of a dead Spanish bayonet, Yucca whipplei.
California Carpenter Bee, Xylocopa californica californica Cresson
This species is 20 to 24 mm long, and both sexes can be predominantly either metallic blue or metallic green, with dusky wings. The pronotum of the male has white, yellow, or orange pile, and the entire first abdominal segment has whitish hairs. These bees nest in redwood and incense cedar in the north Coast Ranges and the Sierra Nevada of California, and in the Cascade Mountains of Oregon.
The subspecies X. c. arizonensis Cresson is 15 to 20 mm long. It is always dark blue, and its wings are blackish, with a strong violaceous tinge; they are more nearly opaque than those of the type. Also, the male has white hairs only on the sides of the first abdominal segment, unlike the type, which has them on the entire segment (Essig, 1926; Hurd, 1955). This subspecies occurs in the deserts of Arizona, California, Nevada, New Mexico, Utah, Texas, and Mexico, nesting in various agaves and yuccas.
Still another subspecies, X. c. diamesa Hurd, resembles X. c. arizonensis, but the wings are paler and less strongly violaceous, and the blue abdomen has traces of green. It occurs in the mountains of southern California and northward to Monterey County, and nests principally in Yucca whipplei (Hard, 1955).
Chandler (1958) listed the types of damage done by carpenter bees as follows: "(1) the weakening of structural timbers through the excavation of galleries; (2) excavation of galleries in wooden water tanks (especially in arid western areas), resulting in costly leaks; (3) unsightly defecation streaks on houses or other painted structures; and (4) annoyance."
Although severe structural damage by carpenter bees is rare, some old, uninhabited, or little-used buildings in mountain or foothill areas may eventually become so honeycombed with the burrows of these insects that they will collapse. People are sometimes alarmed by the large size of the bees, their resemblance to bumble bees, and their noisiness. The males are inclined to make rapid flights around the head of a person intruding near nesting sites, sometimes hovering a short distance in front of his face, and they are not discouraged by attempts to swat them. However, the males have no stinger, and are harmless. The females do have stingers, but do not use them unless they are handled or accidentally come into contact with a person (Chandler, 1958). During the period when females are searching for nesting sites, they will circle around persons standing in open areas as if inspecting them to determine whether they are posts suitable for colonization.
Control of Carpenter Bees
An insecticide such as 5% chlordane emulsion in an oil can may be squirted into each hole. A few days later, the holes may be plugged with dowel pins or plastic wood. Merely spraying the infested wood with 27% chlordane spray will keep carpenter bees away for a season, but they will probably come back the following year to reuse old holes and make new ones (Anonymous, 1970f).
Fig. 102. Dry-rot fungus, Poria incrassata. Top, cross section of an infected timber, with dark stain showing limits of fungal infection; bottom, fungal rhizomorphs and typical checkered appearance of infected wood after it has become dry.
Fig. 103. External morphology of a generalized adult lyctia beetle. AN, antenna; ANA, anterior angle of pronotum; CO, coxal cavity; ES, epicranial suture; F, femur; FL, frontal lobe; IN, interspace; ITS, inner tibial spur; LA, labrum; MAX, maxilla; MC, median canaliculation; ME, mentum; MES, mesosternum; MET, metastemum; MF, median fovea; OTS, outer tibial spur; Pc, postclypeus; PCL, postclypeal lobe; POA, posterior angle of pronotum; PRO, presternum; VER, vertex. (From Gerbera, 1957a.)
Fig. 104 Powderpost beetles. A, Lyctus planicollis; B, Trogoxylon parallelopipedum; C, Minthea rugicollis; D, Lyctoxylon japonum. (From Gerberg, 1957a.)
Fig. 105. Southern lyctus beetle, Lyctus planicollis. Adult, and pupa in chamber.
Fig. 106. Lateral, dorsal, and ventral views of the southern lyctus beetle, Lyctus planicollis.
Fig. 107. Two eggs of Lyctus planicollis in place (Photo by J. G. Pratt, from Christian, 1940b.)
Fig. 108. Differences between lyctid and anobiid larvae. Top, larva and leg of Lyctus sp.; bottom, larva and leg of Anobium punctatum (Credit to Hickin, 1963a.)
Fig. 109. Southern lyctus beetle, Lyctus planicollis. Top, adult emerging from wood; bottom, an emergence hole and damage to ash molding.
Fig. 110. Black polycaon, Polycaon stoutii.
Fig. 111. Leadcable borer, Scobicia declivis. Bottom, adult pupa, and larva; top, damage to seasoned oak.
Fig. 112. Leadcable borer, Scobicia dectivis. Adult; eggs (arrow) in pores, about 2.5 mm from the egg gallery; and full-grown larva. (From Burke et al., 1922.)
Fig. 113. Bamboo borer, Dinoderus minutus.
Fig. 114. A bostrichid (Heterobostrychus aequalis) occasionally found in wood products from the Orient.
Fig. 115. Representative species of each of 6 genera of Anobiidae. A, Anobium punctatum; B, Xestobium rufovillosum; C, Hemicoelus carinatus; D, Pyiobium sericeum; E, Ptilinus ruficornis; F, Xyletinus peltatus. The line at the side of each specimen represents 1 mm. (After White, 1962.)
Fig. 116. Eggs of Anobium punctatum wedged in a crevice of birch plywood. (From Hickin, 1963a.)
Fig. 117. California deathwatch beetle, Hemicoelus gibbicollis. (From Doane et al., 1936. Used with permission of McGraw-Hill Book Company.)
Fig. 118. Damage by California deathwatch beetle, Hemicoelus gibbicollis. Top, galleries, exit holes, and metric scale; bottom, exit holes at surface of Douglas-fir lumber.
Fig. 119. A pest control operator's fumatorium with door open. (Courtesy Columbia Pest Control Company.)
Fig. 120. Portable gastight fumigation tent. Left, tent opened for entry; right, tent after closure. (Courtesy RFD-GA, Ltd., Godalming, Surrey, England.)
Fig. 121. Adults and an immature larva of the newhouse borer, Arhopalus productus.
Fig. 122. Oldhouse borer, Hylotrupes bajulus. Top, female (left) and male; bottom, larva in situ. (Courtesy United States Forest Service.)
Fig. 123. Some common cerambycids. A, Ergates spiculatus; B, Monochamus scutellatus; C, Rosalie funebris, D, Eburia quadrigeminata.
Fig. 124. Nautical borer, Xylotrechus nauticus; adult and larva.
Fig. 125. Neoclytus conjunctus (female), a longhorn beetle that commonly emerges from firewood. (From Linsley, 1964.)
Fig. 126. Adult and larva of a common Pacific Coast buprestid, Dicerca horni.
Fig. 127. Golden buprestid, Buprestis aurulenta (left); green buprestid, B. langii (right)
Fig. 128. Galleries of 2 bark beetles, Dendroctonus brevicomis (top) and Ips confusus (bottom), when bark has been removed from infested pine trees. (Courtesy D. L.Wood.)
Fig. 129. Western pine beetle, Dendroctonus brevicomis, adult and larva. (From Hopkins, 1909.)
Fig. 130. California fivespined ips, Ips confusus. (From Doane et al., 1936. Used with permission of McGraw-Hill Book Company.)
Fig. 131. Typical "compound ambrosial tunnels" of a scolytid ambrosia beetle, Monarthrum scutellare in wood of live oak, Quercus agrifolia. (Courtesy D. L. Wood.)
Fig. 132. Striped ambrosia beetle, Trypodendron lineatum (Drawing by C. S. Papp.)
Fig. 133. Two ambrosia beetles. Western hemlock wood stainer, Gnathatrichus sulcatus (left); Wilson's wide-headed ambrosia beetle, Platypus wilsoni (right). (From Doane et al., 1936. Used with permission of McGraw-Hill Book Company.)
Fig. 134. Gallery systems of 2 ambrosia beetles. Left, galleries of Gnathotrichus sulcatus (A) and Platypus wilsoni (B); right, larval cells dug out along the main gallery by larvae of Gnathotrichus sulcatus. (Courtesy D. L. Wood.)
Fig. 135. Lesser shothole borer, Xyleborus saxeseni.
Fig. 136. Ambrosia beetle tunnels in studs that were to be used in house construction.
Fig. 137. Stains in wood caused by the ambrosia beetle Trypodendron lineatum. (Courtesy D. L. Wood.)
Fig. 138. A woodwasp, Sirex longicauda; adult female and larva.
Fig. 139. A woodwasp, Sirex juvencus. A. female commencing to oviposit in a balsam fir tree; B, oviposition hole containing 2 eggs (arrow); C, second- and third-instar larvae boring at right angles to oviposition hole; D, pupa (From Stillwell, 1966.)
Fig. 140. Left, paired intersegmental sacs (arrows) of a female Sirex juvencus that are located anteriorly to the base of the ovipositor; right, fungal oidia taken from the intersegmental sacs. (From Stillwell, 1966.)
Fig. 141. Taxonomic characters of woodwasps. A, forewing of Sirex; B, dorsal view of head and antenna of Xeris; C, fore- and hindwing of Tremex; D, antenna of Tremex; E, anal region of hindwing of Urocerus; F, dorsal view of head of male Xeris tarsalia; G, dorsal view of head of male Xeris morrisoni; H, cornus and ovipositor of Sirex longicauda; I, cornus and ovipositor of Sirex obesus; J, cornus and ovipositor of Sirex cyaneus; K, cornus and ovipositor of Sirex juvencus californicus; L, cornus and ovipositor of Sirex behrensii; M, cornus and ovipositor of Sirex areolatus; N, cornus and ovipositor of Xeris tarsalia, 0, cornus and ovipositor of Xeris morrisoni; P, lateral view of head of female Xeris morrisoni; Q, lateral view of head of female Urocerus californicus. (From Middlekauff, 1960.)
Fig. 142. A woodwasp, Sirex behrensii.
Fig. 143. Top left, pellets of western drywood termite, Incisitermes minor; top right, borings of valley carpenter bee, Xylocopa brasitianorum varipuncta; bottom, borings of a carpenter ant, Camponotus clarithorax.
Fig. 144. Some California carpenter ants. A, Camponotus nearcticus; B, Camponotus hyatti, C, Camponotus clarithorax; D, Camponotus vicinus; E, Camponotus semitestaeus; F, Camponotus laevigatus. (Courtesy R. R. Snelling.)
Fig. 145. The mountain carpenter bee, Xylocopa tabaniformis orpifex, and its galleries and cells in a cedar shake. In some cells are immature bees in various stages of development.
Fig. 146. The valley carpenter bee, Xylocopa brasilianorum varipuncta. Left, male; right, female.
Fig. 147. A male valley carpenter bee emerging from a tunnel in the trunk of a yucca.