| Bug Pests | Beetle Pests | Miscellaneous Pests | Figure Captions
Contents of Chapter
- SLUGS AND SNAILS
- INSECTS FEEDING IN BEE COMBS IN BUILDINGS
- SWIMMING POOL PESTS
- INSECTS IN MAUSOLEUMS AND CEMETERIES
This chapter is devoted to pests, or presumed pests, that do not appear to fit appropriately into the specific categories mentioned elsewhere, although a few are also mentioned briefly in other chapters. Some are included here only because they evoke fear or curiosity, particularly among city dwellers, even though they are harmless. They are therefore responsible for more calls to entomologists and pest control operators than are justified by their importance as pests or nuisances. Others can be serious pests, usually under certain climatic or environmental conditions that result in a rapid increase of a species to epidemic proportions. Residential or other buildings may be entered merely because they are in the path of a mass migration of some obnoxious species. In other cases, the pests are seeking a protected harborage. Although certain invaders, such as crickets, may consume or damage food or fabrics, none enter a building for these specific purposes.
SLUGS AND SNAILS
Slug and Snail species
- Gray garden slug, Deroceras reticulatum (Müller)
- Longnecked slug, Deroceras laeve (Müller)
- Gray field slug, Deroceras gracile (Rafinesque)
- Banded slug, Lehmannia poirieri (Mabille)
- Spotted garden slug, Limax maximus L.
- Tawny garden slug, Limax flavus L.
- Greenhouse slug, Milax gagates (Draparnaud)
- Giant West Coast Land Slugs (Arionidae)
- European brown snail, Helix aspersa Müller
In areas where climatic conditions are suitable, slugs and snails (Molluscs: Gastropods) can be pests not only in the garden, but also by crawling onto walks, porches, walls, and into doorways or basements. In such places they are not only unsightly, but also leave slime trails that remain visible for many days. When accidentally crushed underfoot, they are not only messy, but are sources of almost traumatic revulsion in some people.
Slugs and snails hide during the day in damp places, such as under boards, rock piles, low-lying shrubs, damp refuse and litter, and dense vegetation of all kinds. Beds of ivy are particularly conducive to heavy infestations of these gastropods. They may be seen during daylight mostly in the early morning and particularly after a rain, or if the lawn and adjacent vegetation have been sprinkled the preceding day. At that time, the pests are generally on their way back to their daytime hiding places, avoiding dry or dusty areas or sharp objects if they can. Snails may sometimes be seen at midday, usually firmly attached to walls, fences, tree trunks, or their food plants. When dry conditions prevail, they seal the opening of the shell with a mucous secretion that becomes a parchment-like sheet called the operculum; this finally becomes hard and leathery. They can then exist in a dormant condition for as long as 4 years. With the return of favorable conditions, the operculum is rasped away by the snail's mandible. Snails can survive lower humidities and lower temperatures than slugs (White and Davis, 1942).
Snails and slugs are garden pests, particularly of tender, young seedling plants and of berries and other fruits. They may cause only surface scars, or may make deep holes in the fruit, besides covering it with the mucus they deposit when crawling.
Morphological Differences Between Slugs and Snails
Slugs are less conspicuous than snails, and are not so well known to most people. Whereas snails are characterized by the coiling of the "visceral hump" into a spiral shell, in slugs the shell is vestigial, and is concealed by the "mantle" situated on the dorsum. Slugs and snails belong to the same order (Stylommatophora), and are similar in structure and biology. They glide along by means of a long, flat, muscular organ known as a "foot." Mucus, which is constantly secreted by glands in the foot, facilitates movement. Slugs and snails are hermaphrodites, and mutual fertilization takes place; both individuals may lay eggs.
There are at least 20 species and subspecies of slugs in California, but only the limacids are common, and in fact they are often serious pests of home garden plants as well as commercial field crops. Except for the indigenous Deroceras laeve, the injurious limacids are all species that have been introduced into North America from the Old World, some at least a century ago. A survey of slugs attacking orange fruit on dooryard and orchard trees in southern California revealed that 3 species (figure 351) appeared to predominate (Ebeling, 1959). (See also, figure 344, chapter 11.) The 3 species were often found together in great abundance beneath orange trees, where their damage to fruit and foliage was visible, usually on the "skirts" of the trees near the points at which they contacted the ground. The orange fruits and foliage were probably only parts of the slugs' diet, for they can also feed on decaying vegetable matter; on fungi or molds; on dead, injured or slow-moving insects; and on sowbugs or earthworms that can be found in the decaying litter in such places as beneath orange trees. Slugs feed on an extremely wide variety of vegetable and animal matter. A check list of California land slugs was prepared by Lange (1944).
Some Important Species
The species found in greatest abundance in the author's survey was the gray garden slug, Deroceras reticulatum (Müller) [= agreste (L.)] (figure 351, A and B), native to Europe, and now one of the worst pests of garden and field crops, especially in humid coastal areas. It is 35 to 50 mm long, ranges in color from buff to brown or gray, and exudes a milky slime when touched.
The longnecked slug, Deroceras laeve (Müller), is an almost cosmopolitan species that invades gardens with D. reticulatum, particularly in the San Francisco Bay region. It is about 32 mm long, and is usually various shades of amber, without spots or markings, but is sometimes blackish, with the head and tentacles smoky. In live individuals, the mantle appears to have a circular orangebrown area. A characteristic feature is its long neck which, when extended, is almost as long as the mantle.
The gray field slug, Deroceras gracile (Rafinesque) or Agriolimax campestris (Binney), considered to be a form of D. laeve by Pilsbry (1948), occurs in all parts of the United States. It is a small species, seldom more than 25 mm long, and is buff to almost black. The slime is clear, not milky as in D. reticulatum. According to A. G. Smith (correspondence), there have been many introductions of the European D. laeve into the United States, particularly into central California, and it is these that are called "longnecked slugs." Smith has found the indigenous form of D. laeve, as recognized by Pilsbry, in many places all through the Sierra Nevada and also in his garden in Berkeley. He has never found the "longnecked" race in his garden, although it is prevalent in Golden Gate Park in San Francisco and in nurseries and cultivated areas in Alameda and Contra Costa counties.
The banded slug, Lehmannia poirieri (Mabille) Limax marginatus (Müller)] (figure 351, C and D), another European species, may attain a length of from 50 to 75 mm, and has a general light brown color, with parallel, longitudinal, gray, dark-brown, or black bands on the mantle. There are 3 such bands in immature slugs, but the middle band tends to disappear with approaching maturity. These slugs are basically fungus-feeders, but they are also among the principal citrus pests, and will feed on garden plants and underground tubers.
The spotted garden slug, Limax maximus L., is the largest of the European "gray" slugs introduced into western America, exceeded in size only by the indigenous Agriolimax species (Hanna, 1966). It prefers human habitations and, although like other limacids it is a fungus-feeder by preference, it often causes injury to garden plants. It is yellowish gray or brown, with large, irregular black spots, and is usually about 100 mm long, but may reach a length of 200 mm. The mature specimens have a dark-spotted mantle, but in immature slugs these spots may be united into bands.
The tawny garden slug, Limax flavus L., is widely distributed in the eastern and southern parts of the United States, and was recorded in California as early as 1903. It is a large species, 75 to 115 mm long, and is exceeded in size only by L. maximus among the introduced European species (Hanna, 1966). It is yellowish green, with yellow spots, and exudes a yellowish slime when disturbed. Its mantle consists of a series of concentric grooves, giving it a reticulate appearance, and the ocular tentacles are bluish. This slug is gregarious, and may be found under garbage cans, in basements, wells, drains, and under doorsteps. It may be found in nurseries, and also does some damage to garden plants.
The greenhouse slug, Milax gagates (Draparnaud) (figure 351, E and F), was introduced into North America as early as 1872. It is very destructive to nursery, garden, and field crops in California, and its burrowing habits make it a pest of root crops. It may attain a length of 40 to 70 mm, is dark gray or black, has an oval or diamond-shaped groove on the center of the mantle, and has a prominent, sharp, dorsal keel extending back the entire distance behind the mantle. The keel is especially conspicuous when the body is contracted (Lange, 1944).
Giant West Coast Land Slugs (Arionidae)
The giant slugs are generally too rare to be even mild nuisances, and only occasionally do some species damage garden plants. However, because of their large size, they are often the subjects of inquiry when found. They do not thrive in cultivated areas, and are most likely to be seen by the urban population in damp, unmolested areas, such as in the state parks of the redwood belt of northern California (e.g., Muir Woods). The only natural enemies of the giant slugs are apparently ducks and garter snakes (Thamnophis). The thick, viscous coat of slime on their bodies is very bitter, and they are shunned by most potential predators (A. G. Smith, personal communication).
The largest and most widely distributed of the giant slugs is the giant yellow slug, giant redwood slug, or banana slug, Ariolimax columbianus (Gould). It occurs in parts of Alaska, west of the Cascade Mountains in British Columbia, Washington, and Oregon, in California south to the Salinas Valley on the coast, and at least as far south as Tuolumne County on the western slopes of the Sierra Nevada. The adult of this very large slug weighs from 35 to 72 grams, and its foot varies from 18.5 to 26 cm in length when fully extended. The ground color is described as "deep, olivaceous green, tan-green, ochraceous, ochraceous-yellow, slate-green, or intermediate shades," with the mantle of the same color. According to Lange (1944), this species occasionally invades gardens to feed on vegetables and other plants. There is also a form that is spotted or blotched with black. The ground color of A. columbianus, including the mantle, is very variable, but never attains the light-yellow color of the other species of the genus, which are less variable. The color of individual slugs will change with age and alterations in food, moisture, and light. There is also a smaller and more slender subspecies, A. c. stramineus Hemphill, distributed south and west of the Salinas Valley, from the Monterey peninsula to at least Ventura County and in Santa Cruz and Santa Rosa islands. It weighs 20 to 27 grams, and its foot is 13 to 16 cm long. Its ground color is vitreous lemon-yellow or light straw-color (Mead, 1943; Pilsbry, 1948).
Ariolimax californicus Cooper occurs in San Mateo County and northwestern Santa Clara County in coastal central California. It is a smaller species than A. columbianus, the adults weighing 25 to 42 grams and having a foot length of 17.5 to 20 cm. The ground color, including the mantle., is vitreous butter-yellow, rarely ochraceous yellow. This slug occasionally invades vegetable fields and gardens, but usually does not do extensive damage (Lange, 1944). Ariolimax c. brachyphallus Mead occurs on the San Francisco peninsula. It is the smallest slug of the genus, weighing 17 to 23 grams, and has a foot length of 12.5 to 15 cm. Its ground color is ochraceous or ochraceous brown, and its mantle is usually ochraceous yellow and rarely the same color as the remainder of the body.
Ariolimax dolichophallus Mead is limited to coastal central California, from northern Santa Cruz and western Santa Clara counties to the Salinas Valley. It is a slender species, with adults weighing 20 to 39 grams an a foot length of 15 to 18 cm. Its ground color, including the mantle, is opaque butter-yellow. It obtains its name because of its extremely attenuate apical phallus (copulatory organ) being very long occasionally it may be longer than the slug itself (Mead, 1943; Pilsbry, 1948).
European Brown Snail, Helix aspersa Müller (Helicidae)
The European brown snail has been widely disseminated throughout the world by being accidentally or intentionally introduced on plants. In California, it is found in most residential and cultivated areas, from San Diego to Sonoma counties. It was intentionally introduced from France between 1850 and 1860 and "planted" among the vineyards along Guadalupe Creek in Santa Clara County, and later in San Francisco and Los Angeles (Basinger, 1931). Although this species has some value as an article of food in certain European countries, other kinds are more popular. It is rarely eaten in California, except by an occasional European immigrant. It is one of the most destructive and prolific dooryard and garden pests in the state, which would be free of destructive snails if it had not been deliberately introduced.
Description. The shell of this snail (figure 352) is grayish yellow and brown. The brown is usually in 5 interrupted bands, the second and third ones being ordinarily confluent, giving the appearance of a single band. All the bands may be united in some individuals. When fully developed, the shells have 5 or 4.5 whorls, and are 2.5 cm or more in diameter. The shell's form is that of a dextral or right-hand spiral, the sinistral or left-hand aspect being very rare. The body is light to dark gray, and is about 6 cm long when fully extended. (Basinger, 1931).
Life Cycle. Oviposition usually occurs within 3 to 6 days after fertilization. The snail selects a spot where the soil is damp, and prepares a nest for the eggs in the ground at a depth of 2.5 to 4 cm (figure 353). The eggs are white, somewhat translucent, spherical, and about 3 mm in diameter. The egg mass contains an average of 86 eggs. After ovipositing, the snail closes the opening of the nest with a little mound of earth and excrement to conceal its location. The young snails have shells of somewhat more than 1 whorl when they hatch. They usually remain in the nest for 2 to 4 days, then work their way to the surface. Two years are required to reach maturity.
Control of Slugs and Snails
After removing as many as possible of the favored hiding places of slugs and snails, sprays or poison baits may be applied, the latter usually being preferred. Baits are applied in places frequented by these gastropods, such as along the edges of dense vegetation bordering lawns. This should be done when plenty of moisture is present, such as after a sprinkling or following a rain. Pelletized baits should not be used where dogs are present, for dogs will eat them.
For many years, a bait containing 5% metaldehyde (C2H4O)n or 3.25% metaldehyde and 5% of an arsenate has been used for the control of slugs and snails. The bait containing only metaldehyde is particularly effective against slugs and during the warmer periods of the year. The arsenate increases its effectiveness under adverse conditions or against snails, providing greater toxicity, while the metaldehyde continues to act as an attractant. The bait should be applied every 7 to 10 days until control is accomplished. Also available is a 20% spray concentrate which is diluted with water to produce a 0.25% spray.
The carbamate insecticide Zectran® (table 1, chapter 2) is also an effective molluscicide, and is available as 2% granular bait or a 2E (2 lb per gal or about 1 kg per 4 L) emulsifiable concentrate. The bait kills the pests in 3 to 5 days and lasts for about 2 weeks. It should be reapplied in about 3 weeks. The emulsifiable concentrate is diluted to make a spray of 0. 1% toxicant. It is said to be more effective than metaldehyde spray, even though it kills more slowly.
The most recently developed molluscicide is the carbamate insecticide Mesurol®, 3,5-dimethyl4-(methylthio)phenol methylcarbamate, also sometimes expressed as 4-(methylthio)3,5-xylyl methylcarbamate. (See table 1, chapter 2.) Mesurol, in both wettable powder and pellet formulations, was found to be superior to metaldehyde against the gray garden slug, particularly under damp or cold conditions (Wouters, 1970). It is available as a 20% granular bait, and is said to be the most rapid-acting of the molluscicides, giving good control in 1 or 2 days. Only a single treatment is usually required (NPCA, 1973).
These are small crustaceans, nearly all of which are laterally compressed, giving them a shrimplike appearance. Among the Amphipoda is a species that may invade the home following rain or prolonged watering of the vegetation in which it seeks harborage.
Talitroides sylvaticus (Haswell) (Talitridae)
These small amphipods (figure 354) are recorded from Australia, several Pacific islands, including Hawaii, and from California and Louisiana (Mallis, 1969). They are in the same family as the "beach fleas" that live beneath piles of seaweed and other drift material near high-tide mark on the beach.
Live specimens of T. sylvaticus are brownish black, and approximately 8 mm long when mature, but turn red when they die (plate VIII, 7), and this is the condition in which they are usually seen by the homeowner, for they do not live long after entering a house. They may be found in coastal southern California in and on the ground in damp places, particularly under ivy, where they sometimes occur in enormous numbers, jumping about like fleas.
Although terrestrial amphipods require damp locations, excess moisture forces them to seek drier locations, and they may then become accidental intruders into the home. The lack of a waterproof wax layer which forces them to seek damp locations is also a hazard to them if their environment becomes too wet, for they are not only susceptible to desiccation but also to a lethal rate of water uptake by osmosis. The author observed after an unseasonable early rainfall of 0.3 in. (8 mm) in September, 1963, that T. sylvaticus migrated away from an ivy patch, and large numbers found their way into a near-by house. These were dead the following day, apparently, as observed by Mallis (1942, 1969), finding their new environment too dry. Again, following early rain in October, 1966, a local resident brought in large numbers of the amphipods, found in his home, for identification. During the following winter they became so troublesome that he sprayed his ivy with a 0.5% diazinon emulsion and found it to be an effective control measure.
Pseudoscorpions or "false scorpions" (order Chelonethida) (figure 35, chapter 4) are arachnids that sometimes invade the home and should be recognized as harmless. Outdoors they may be found in leaf mold, or in the nests of birds, mammals, and insects, under stones, and beneath bark, where their disklike webs, spun with their chelicerae, are often abundant. The web forms a sort of cocoon in which the pseudoscorpion molts and hibernates. Pseudoscorpions prey on other arthropods, such as small insects and mites. Species of the genus Chelifer are sometimes found crawling about in the house.
In common with the pseudoscorpions, harvestmen (order Phalangida), also known as "daddy-longlegs," should be recognized as harmless arachnids (figure 38, chapter 4). They are often misidentified as spiders of some sort. Although principally nocturnal, they are often seen in large numbers in cloudy weather, and may invade the home.
They eat insects, both living and dead, particularly aphids, but also eat vegetable matter, and can be injurious to tender plants. Insects are seized by the leglike pedipalps, passed to the chelicerae, macerated, and the liquids are consumed, along with some coarse particles. Phalangium and Liobunum are familiar genera.
The solpugids (order Solpugida), sometimes known as "sun spiders" or aranas del sol, are very swift and agile arachnids, mostly nocturnal (figure 39, chapter 4). Their huge chelicerae may impart a fearsome appearance, but they do not have venom glands, and are harmless. They feed on other small arthropods. Solpugids are found in warm, dry, desert areas. They do not spin webs. The female lays her eggs in a burrow in the ground and stays there until they are hatched. During the day, solpugids commonly remain under stones, boards, logs, and other objects that may cover their burrows. They seek their prey at night, catching it on the run, and occasionally find their way into homes. The principal genera in the United States Southwest are Ammotrecha, Eremobates, and Hemepotrecha.
Mite Species List
- Clover mite, Bryobia praetiosa Koch
- Brown wheat mite, Petrobia latens (Müller)
- Winter grain mite, Penthaleus major (Dugès)
Mites are discussed at considerable length in chapters 7 and 9, entitled "Pests of Stored Food Products" and "Pests Attacking Man and His Pets." Some of the species discussed in those chapters may occasionally be seen crawling about on walls, cabinets, furniture, and other interior surfaces. There is only 1 important mite species (or complex of forms and species) that normally feeds on plants outdoors and then invades the house - the clover mite. It sometimes enters homes in such numbers as to become an important pest.
Clover Mite, Bryobia praetiosa Koch (Tetranychidae)
This is a cosmopolitan species that infests many trees, shrubs, flowers, grasses, and agricultural crops; it is found on at least 200 species of host plants. It is probably the mite of most frequent concern to homeowners. Aside from being pests on surrounding trees and other vegetation, clover mites can invade the home, usually around windows, under doors, or through cracks in walls or masonry, in such large numbers as to give infested surfaces such as walls, windows, and floors a reddish appearance. If crushed, they will leave reddish spots or smears. The problem is accentuated if lawn or other grass is allowed to grow close to the foundation and is heavily fertilized, resulting in lush growth (Spear, 1954).
Biology. The adult clover mite (figure 355) averages about 0.75 mm in length, and may be rusty brown, olive green, or dark red. The best distinguishing feature is the pair of front legs that are longer than the body and about twice the length of the other legs. The young stages are bright red. Ordinarily, the smooth, spherical, red eggs are laid on trees and other vegetation throughout the summer and fall. Those laid in late fall hatch the following spring, and may sometimes be seen in such numbers on the limbs of trees, particularly at crotches, as to give the appearance of brick dust. They are also sometimes seen on the foundations or outer walls of buildings.
Clover mites reproduce parthenogenetically, that is, without fertilization. Males have not been found in the United States, and only rarely in a few other parts of the world. A female will lay about 70 eggs. This species has a larval stage, 2 nymphal stages (protonymph and deutonymph), and an adult stage. About 1 month is ordinarily required to complete a generation outdoors, the optimum temperature for development being 69 °F (21 °C). Above 75 °F (24 °C), the eggs become dormant, and they are also inactive below 40 °F (4 °C). In Illinois and Pennsylvania, the form of clover mite that infests dwellings becomes dormant during May and remains so until September (Snetsinger, 1967). According to Spear (1954), in the eastern states the mites may be found in infested houses from November until May or June. They can invade a house in enormous numbers; 250,000 were estimated to be present at one time on the floor of a bedroom.
Other Species and Forms
Occasionally, what are presumed to be clover mites invading the home are actually the brown wheat mite, Petrobia latens (Müller) (Tetranychidae), and the winter grain mite, Penthaleus major (Dugs) (Enpodidae), or these species in mixed populations with the clover mite. Of greater interest, however, is the fact that there are 15 to 20 different morphological forms of the clover mite, with different behavioral and seasonal occurrence patterns. Snetsinger (1967) conceived a hypothetical clover mite control job in which there might be 7 different forms (table 8) on the premises, of which only one, the "dwelling and tree-trunk" form, would be a potential pest. [According to R. N. Hawthorne (correspondence), in California both Bryobia rubrioculus and B. praetiosa, the "tree-trunk form," invade the home.] This form lays its eggs under bark and in cracks and crevices in building walls. The seasons of major mite activity in the eastern states are spring and fall, with some activity during warm spells in winter. On a sunny winter afternoon, when the air temperature is 32 °F (zero °C), the temperature on the south side near the foundation of a house may be 60 °F (16 °C) or more because of radiated heat, and the mites may be actively feeding.
The period when the mites are most likely to enter dwellings varies with the climate - in April or May in Pennsylvania, but earlier farther south and later farther north. In California, pest control operators receive most of their calls for mite control in the spring months, with a secondary peak of activity in the fall. Infestations are usually most severe on recently occupied and landscaped property. After populations of natural enemies have had opportunities to become established, the mites become less of a problem. There are at least 62 species of predators that attack the clover mite. [Eight are spiders, 15 are mites, 5 each are thrips, anthocorid bugs, and mirid bugs, 15 are coccinellid beetles, and the rest are in other families and orders of arthropods (Snetsinger, 1960).] Also, the grass near the foundation is likely to be replaced by ornamental plantings, and the vigor of the remainder of the lawn decreases, both tending to reduce the mite population (Snetsinger, 1967).
The Clover Mite as an Ectoparasite
A new role for Bryobia praetiosa as a pest was revealed in a report from Argentina that, since 1964, this species has occasionally been ectoparasitic on man, always in October (a spring month in that area). Attacks have been recorded in schools, laboratories, and houses, particularly against children. Usually, skin irritation as well as sores resulting from the rubbing of affected parts was observed. In some persons, the attacks were followed by listlessness and loss of interest (Maury and de Alzuet, 1970).
Control of Clover Mites
The dwelling and tree-trunk form of the mite feeds on grass near the foundations of dwellings and near the bases of trees. An acaricidal barrier on a strip of bare soil 18 in. (45 cm) wide around the outside of a building can reduce the number of mites reaching it by about 90%. Acaricides may also be applied under high pressure to the foundation of a dwelling, so as to penetrate into cracks and crevices in the wall where the mites seek protection against cold and desiccation and where they lay their eggs. It may also be advantageous to spray for a distance of about 15 ft (5 m) from the foundation. A grass-free strip around buildings has been found to be about as effective as acaricide applications, but a combination of the 2 control measures will definitely give the most satisfactory results.
Acaricides such as chlorobenzilate and ovex can be safely used around windows and doorsills Or similar points of entry. Treatments within the house give only temporary relief if no control measures are practiced outside (English and Snetsinger, 1957; Snetsinger, 1967). Inside residences, mites can be removed with a vacuum cleaner so as not to crush them and to avoid making the red smears that result if a cloth or brush is used.
Earwig Species List
- European Earwig, Forficula auricularia L. (Forficulidae)
- Striped Earwig, Labidura riparia (Pallas) (Labiduridae)
- Ringlegged Earwig, Euborellia annulipes (Lucas) (Carcinophoridae)
- African Earwig, Euborellia cincticollis (Gerstaecker)
The common name, "earwig," is derived from a European superstition of ancient origin that these insects enter the ears of sleeping persons and bore into the brain. However, despite the formidable appearance of their caudal forceps (figure 356), they are practically harmless to man. There have been reports of some species occasionally nipping people with their forceps and drawing blood. In the United States, apparently the only record of injury by earwigs was reported by Bishops (1961), one of whose toes was bitten by a nymph of Labidura riparia inside the shoe, causing profuse bleeding. The insect appeared to be distended with ingested blood.
Earwigs (order Dermaptera) feed on live or decaying vegetation as well as live or dead insects. When a female was offered living insect prey, she immediately grasped it in her forceps, and while still holding it, she turned her body in a half circle and ate the insect (Klostermeyer, 1942). Earwigs at times cause damage to cultivated plants, but can also become household pests by invading a home in large numbers and being severe nuisances.
Earwigs are medium-sized insects, ranging in the United States from 5 to 25 mm in over-all length. They are elongate and flattened, have a tough, shiny exoskeleton of various shades of brown, or are sometimes black. The mouthparts are of the biting type. The metamorphosis is gradual, usually with 4 or 5 nymphal instars. When wings are present, the first pair form very short, usually truncate, veinless, hard wing covers, making them resemble superficially the staphylinid or rove beetles. The second pair of wings are fanshaped, with a peculiar radial venation. When not in use, they are folded in a complicated fashion into a compact mass that is almost completely covered by the abbreviated wing covers. The body terminates in a pair of strong, movable forceps or pincers, those of the males being larger and more caliperlike. They are used for defense, capturing prey, probing the area inside a narrow crevice, and to a lesser extent for folding and unfolding the wings (Morgan, 1923; Essig, 1942). Morgan (1924), in an investigation of Labidura bidens Olivier, could find no evidence that the forceps were used in mating, as had sometimes been reported.
Earwigs are nocturnal in their habits, hiding during the day in moist, shady places under stones or logs, in cracks in the soil, or in almost any secluded place. Their ways are similar to those of cockroaches, including their gregarious nature, their habit of cleaning their appendages with their mouthparts (Bharadwaj, 1966), and the fact that they are repelled by dust (Crumb et al., 1941). Neither eggs nor nymphs are able to withstand prolonged desiccation.
Maternal Care of Eggs and Young
The female lays smooth, oval, pearly-white, yellowish or cream-colored eggs in a chamber in the ground. She exhibits an instinct that is rare among insects - maternal care of the eggs and young (figure 357). Referring to the European earwig, Forficula auricularia, Crumb et al. (1941) stated:
The eggs were never known to hatch in the absence of the female, probably because it is necessary for them to be kept in a moist situation, and yet protected from mold. The care of the eggs includes "licking," turning as done by a hen, and frequent shifting of their position, now in a layer on the side of the cell and now, perhaps, in a heap at the bottom. In spite of her solicitude for them, the female will eat her eggs readily if conditions become too unfavorable or even if she is disturbed too much.
For the first few days after the eggs hatch, the female keeps the nest closed. It is opened later, but she guards against intruders, using her forceps as weapons. She brings in food for the young, which remain inside or close to the nest until after their first molt (Fulton, 1924a, b; Crumb et al., 1941).
The female of the striped earwig, Labidura riparia, also remains with her eggs in a specially constructed chamber, grooming the eggs at intervals until they hatch 8 to 10 days later. She does not eat during the incubation period. The newly hatched nymphs remain in the chamber with the female for another 2 to 4 days. She will eat the nymphs if the nest is disturbed (Caussanel, 1970).
European Earwig, Forficula auricularia L. (Forficulidae)
The European earwig (figures 356 and 357) is a cosmopolitan species that was first reported in the United States in Newport, Rhode Island, in 1901 and in Seattle, Washington, in 1907. It is now found in many areas throughout the country and in southern Canada. These earwigs require high humidity for continuous development. In one experiment at an average relative humidity of 48% they were all dead in 12 days (Crumb et al., 1941). Probably in semiarid areas such as southern California, the insects can survive only because they can find secluded, moist places in which to spend most of their time. They thrive best in cool, moist climates. On the other hand, prolonged wet periods in the spring when the young earwigs are hatching cause high mortality among them.
Description. Adult females, including forceps, are about 16 mm long. Some adult males are about the same size, but others are considerably larger. As with the Dermaptera in general, the males have larger and more caliperlike forceps (figure 356). With regard to the size of the forceps, the males are dimorphic, the forceps being about 3.5 mm long on some and 7 mm long on others (figure 358, F and H). Those with longer forceps usually have much larger bodies. The general color is dark reddish brown, with the head decidedly reddish and the wing covers, legs, and antennae paler. On each side of the dorsal aspect of the third and fourth abdominal segments (second and third visible segments) are the openings of glands that discharge small drops of liquid if the insect is picked up. This liquid is probably responsible for the peculiar odor of earwigs (Fulton, 1924a).
Habits and Life Cycle. Pairs of European earwigs dig into the soil in the fall, and usually hibernate in cells 3 or 4 cm beneath the surface. In observations made in mid-January, Fulton (1924a) found eggs in some cells and, when no eggs were present, the body of the female was full of them. The eggs are about 1 mm long, pale yellow or cream-colored, opaque, and broadly elliptical. As they develop they become larger, whiter, and more translucent. The males leave the cells in January, and can be seen in numbers until the last of April or May, when some reenter the soil with the females a second time. The females begin to leave the soil in April, most of them appearing on the surface by the middle of May, having spent about 7 months in the soil without food. Some of the females again enter the soil to deposit a second clutch of eggs. Thus, there may be 1 or 2 generations a year.
Under the climatic conditions at Puyallup, Washington, adults entered the soil for hibernation from the latter part of September to the last of October, the period of maximum entrance apparently depending on the advent of cool weather. Many males, an occasional female, and rarely a nymph remained above the surface throughout the winter. The average incubation period for winter egg masses was 72.8 days, and for the second or spring clutch it was about 20 days. There appeared to be about equal numbers of new males and females. In the field, the period required for the development of the 4 nymphal instars was about 68 days, while in the laboratory between 60 and 70 °F (16 and 21 °C), it was about 31 days (Crumb et al., 1941).
Few people have seen earwigs in flight, but Crumb's group observed as many as 20 flights in one day, mostly in bright, warm sunshine. An elevated object seemed to be necessary for takeoff, and the insects were able to rise and fly at least 30 ft (9 m).
Economic Importance. European earwigs are omnivorous, but prefer plants such as mosses, lichens, and algae as food. Some animal food seems to be required, and this includes insects, spiders, mites, and protozoa, alive or dead (Crumb et al., 1941). They occasionally do some damage to flowers, fruits, vegetables, ornamental shrubs, and trees, and have been known to feed on honey in beehives. Damage is small when compared with the numbers of earwigs that are sometimes present. In one investigation, digestive-tract analyses showed the diet to consist largely of lichens and pollen (Dimick and Mote, 1934).
The insects are most abundant in the gardens or homes of urban areas, and around buildings in rural communities. They tend to avoid cultivated or dry land, and sometimes invade houses in enormous numbers. Fulton (1924a) quoted thus from a correspondent:
Literally thousands and thousands of those bugs inhabited my premises last summer. They made it almost impossible to live in my home; they inhabited the sleeping porch till we had to leave it. They work mostly at night, but in the daytime might be found in kitchen drawers, and often burrow an inch into a loaf of bread. They crawl over ceilings at night and drop on the bed, or inhabit themselves in a person's clothing during the night, and while their bite has never proved serious, it is entirely uncomfortable.
With regard to infestations in Oregon, Fulton stated that it was almost impossible to keep European earwigs out by the use of screens, and that they had become so annoying in some districts that property values had depreciated considerably. There were successive importations from Europe of a tachinid parasite, Digonichaeta setipennis Fall, from 1924 to 1929 in Oregon and California, and as high as 38.4% parasitism was recorded (Ritcher, 1966). The European earwig is believed to be less abundant than before the parasites were introduced, but nevertheless it is often a severe nuisance as a house and garden pest. This is indicated by a survey of the opinions of California structural pest control operators as to the relative importance of the 6 most important pests (termites excluded) that they have been called upon to control. These pests, in descending order of importance, were reported to be: in northern California, German cockroaches, ants, earwigs, mice, fleas, and silverfish; in central California, German cockroaches, earwigs, mice, silverfish, brownbanded cockroaches, and black widow spiders; and in southern California, German cockroaches, ants, fleas, oriental cockroaches, earwigs, and silverfish (PCOC, 1973). Earwigs were not listed as to species, but the European earwig was the principal pest species in most areas.
Striped Earwig, Labidura riparia (Pallas) (Labiduridae)
The striped earwig, also known as the shore or riparian earwig, appears to be distributed in tropical and subtropical areas throughout the world. It was first reported in the United States, in Texas, in 1876 (Hebard, 1942). It is now widely distributed in the southern states and in parts of Arizona and California. It apparently became established in the Yuma (Arizona) area in 1952, and spread into the major irrigated farming areas of southern Arizona and southeastern California (Schlinger et al., 1959; Nutting, 1960). It has become widely distributed throughout southern California, and has extended its range northward to scattered areas in the central valley.
Description. This fully winged species is usually larger than the European earwig, ranging from 20 to 25 mm in length - usually slightly less than 25 mm. The color varies from pale brown, with distinct black markings, to chestnut or reddish brown, with the dark markings somewhat merged into the general color. The abdomen is usually banded, and the forceps vary from yellowish to reddish brown and are darker near the tips. The antennae and legs are yellowish. The last segment of the male's abdomen usually bears 2 short spines that are larger and more strongly developed on large specimens. The male's forceps are usually elongate and conspicuously toothed (figure 358, A), but some are shorter and weakly toothed (figure 358, B). The female's forceps (figure 358, C) are close together where they are, attached to the abdomen, and bear short, basal teeth along their inner margins, but these are sometimes hardly noticeable (A. B. Gurney, correspondence).
Life Cycle. Striped earwigs live in subterranean burrows beneath rubbish, mulches, and turf thatches. One female was observed to seal the entrance to a burrow she had made, after depositing 51 eggs within the burrow, tending them, washing them, and moving them about. (The eggs become covered with fungi or desiccated if a female is removed after ovipositing.) The eggs hatched in 7 days, and the first-instar nymphs fed on the egg cases. The nymphs remained in the burrow, and were groomed and manipulated.until their first molt, which occurred in another 7 days. The female then released them from the burrow and lost her maternal interests, devouring any nymphs she could capture. Depending on the amount of food (maggots) and water provided, the nymphs matured in from 49 to 60 days (average 56) at temperatures varying only a few degrees from 78 °F (26 °C) (Clements and Kerr, 1969). Labidura riparia was observed to lay 3 or 4 clutches of eggs per year in Europe (Caussanel, 1970).
Habits. Apparently, all North American species of earwigs are predatory, but. they are also scavengers. Striped earwigs seem to eat any food they encounter, such as garbage, cat and dog foods, or insect carcasses. They are not known to damage plants as the European earwigs do. Most of the earwigs (96.5%) found around structures in Florida in 1967 were Labidura riparia, the remainder being principally the ringlegged earwig, Euborellia annulipes, and a few spinetailed earwigs, Doru aculeatum (Scudder). However, during part of the summer of 1968, D. aculeatum was one of the most common earwigs, when large numbers developed and flew to lights (Clements and Kerr, 1969). Labidura riparia was trapped in flight (toward lights) only on nights after rainfall had occurred the previous day or night. The initial flight coincided with the maturation of the first generation of earwigs (Gross and Spink, 1971).
Economic Importance. In the Gulf states and California, striped earwigs became important household pests during the 1960's. They appeared to be attracted to lights and/or to other insects that were also attracted to lights. Their disagreeable odor, intensified if they are crushed, resulted in this species being particularly detested. Infestations in a residence could usually be detected, because of the characteristic odor, before the insects were seen. Another noteworthy peculiarity of these insects was their inherent resistance to chlorinated hydrocarbons. As a result, the application of 10% granular heptachlor to urban yard and field test plots, which eliminated important predators (imported fire ant and thief ant), greatly increased the striped earwig population (Gross and Spink, 1969).
Ringlegged Earwig, Euborellia annulipes (Lucas) (Carcinophoridae)
This cosmopolitan species was first recorded in the United States in 1884, and is now widely distributed throughout the nation (Bharadwaj, 1966). It has been recorded from every county in southern California as well as in most of the northern counties. It appears to be a native American species (R. N. Hawthorne, correspondence).
Description. The ringlegged earwig is 12 to 15 mm long, wingless, and dark brown to black, with a yellowish-brown undersurface. The legs are yellowish, with femora, and tibiae bearing fuscous rings. The black, 16-segmented antennae have the third, and usually the fourth, segment from the apex white. The female has 8 abdominal tergites, and the male has 10. Typical forceps of male and female are shown in figure 358, D and E, respectively. The nymphs resemble the adults. In the successive nymphal instars, the number of antennal segments is 8 in the first, 11 in the second, 13 in the third, 14 in the fourth, and 16 in the fifth (Bharadwaj, 1966).
Life Cycle. Females can produce as many as 6 clutches of eggs from a single mating (Klostermeyer, 1942), but usually produce 1 to 4 (Bharadwaj, 1966). The eggs average 0.845 mm long, and are at first creamy white and ovate, but later become gray or brownish and kidneyshaped. The average number of eggs laid per female has been recorded as 47 (Klostermeyer, 1942), and as 52.7 (Bharadwaj, 1966). Klostermeyer found the preoviposition period to be an average of 10.8 days; egg stage, 14.3 days; and nymphal stage (5 instars), 80.7 days. Some females lived as long as 7 months after reaching maturity. Females outnumbered males by a ratio of about 4 to 1.
Economic Importance. The ringlegged earwig has been recorded as a pest of Irish and sweet potatoes in storage, in flour mills, breweries, meatpacking plants, and slaughterhouses, damaging the roots of vegetables grown in greenhouses, and as a pest in gardens and nurseries. It was reported as one of the principal pests in corn-processing plants (Gould, 1948). It acts as a carrier of certain endoparasites of fowls in Hawaii. It has become a nuisance by invading houses, particularly in the Gulf states. On the other hand, it is of some value as a predator on certain insect pests, including leafhoppers, beetles, moths, and various stored grain pests (Klostermeyer, 1942; Bharadwaj, 1966).
African Earwig, Euborellia cincticollis (Gerstaecker)
This African species occurs in a few localities in Texas, Arizona, and Nevada. In California, where it was first reported in 1946, it was found in many localities in the southeastern desert. It has since spread as far as the northern part of the central valley. In California, these earwigs have been reported to cause damage to Persian melons where they contact the ground. In Arizona, they have been swept from alfalfa, collected in houses and motels, and seen at lights (Schlinger et al., 1959; Nutting, 1960). Open fields with some type of low-growing plants are favored areas, provided moisture and drainage conditions are favorable. The furrows of seed alfalfa fields are ideal habitats (Knabke and Grigarick, 1971).
Description. These earwigs are black, with a reddish tinge. Their legs are yellow or amber, usually with faint, smoky markings on the femora and tibiae. Mature specimens average 14 mm in length. Some adults are wingless, or have short wings and are easily confused with Euburellia annulipes, which is always wingless (in California) and is similar in general appearance. However, normally in both sexes of E. cincticollis, antennal segments 15 and 16 are white, the remainder being dark brown, whereas in E. annulipes, usually segments 12 and 13 are white. An occasional specimen of either species will have antennae with all segments dark. Specimens of E. cincticollis have only faint, smoky areas on the femora and tibiae, whereas the legs of E. annulipes are prominently black-spotted (Ting, 1951). A distribution map shows E. cincticollis to be limited to interior localities of California, whereas E. annulipes occurs both inland and along the coast (Knabke and Grigarick, 1971).
Euborellia cincticollis, as well as E. annulipes, can be distinguished from the European earwig, Forficula auricularia, in that the latter lacks the white antennal segments, and the forceps also differ greatly in size and shape, being larger and more "forcepslike" in the male (Ting, 1951). Also, in F. auricularia the second tarsal segment is lobed, whereas in the genus Euborellia it is cylindrical (Knabke and Grigarick, 1971).
Life Cycle. The African earwig normally remains almost entirely hidden in the soil at depths of about 2 to 30 cm, or under vegetative growth. Eggs are laid from late April to July and August. Field-collected females produced and brooded several clutches of eggs in the laboratory at 2 to 4 week intervals, averaging a total of 83.7 eggs per female. The average periods from egg to adult were 128 days at 22 to 27 °C, 78 days at 27 to 29 °, and 82 days at 32 to 331. Five nymphal instars were most common at 22 to 27 ° and 6 to 7 instars were most common at 32 to 33 °. One or 2 generations per year were estimated to be produced in the field. Both nymphs and adults were noted to overwinter. Field-collected adults survived as long as 240 days in the laboratory, and were believed to be able to live a year or more in the field. In one investigation, flights of E. cincticollis occurred between July 14 and September 26, but major flights did not occur until August 12. Flights took place mainly from sunset to about 10 p.m. (Knabke and Grigarick, 1971).
Control of Earwigs
European earwigs are strongly attracted by fish oil. This characteristic has been utilized in the preparation of an effective poison bait. One lb (0.45 kg) of sodium fluosilicate is mixed with 12 lb (5.5 kg) of dry bran. A quart (about 1 L) of fish oil is then mixed with the poisoned bran. No water is added. The bait should be applied in the evening beside fences, hedges, woodpiles, around the foundations of buildings, in flower beds, under and in the crotches of trees, and on the lawn. The lawn should not be sprinkled for 2 days after application of the bait. In Oregon, where the bait was developed, most feed and seed stores sell a ready-mixed bait for European earwig control. The bait is poisonous, and should be kept from children, but poultry will not eat enough to be harmed (Anonymous, 1968b). Malathion has been suggested as an effective contact insecticide, but it does not have a long residual action. It should be applied in the evening in the same areas as suggested for application of the poison bait, but of course it should be more uniformly distributed. The earwigs will contact the residue when they come out for their nightly foraging. Malathion may be used as 5% dust or as a spray prepared by mixing 1 cup (240 cc) of 25% wettable powder or 2 tablespoonfuls (30 ml) of 57% emulsifiable concentrate per gal (4 L) of water (Anonymous, 1968b). The earwigs are particularly numerous around heavy growths of ivy. R. N. Hawthorne (personal communication) suggests that not only the ground, but also fences and trees (up to the lower crotches) be sprayed in March and April, after turning over all rocks and boards to expose hidden insects. (He has observed in recent years that the earwigs were ascending pear trees in spring to feed on the opening buds.) Organochlorine insecticides are effective, and if the homeowner uses chlordane to spray his lawn for lawn moths, the spray can be extended to other areas of the yard for good control of earwigs and ants.
Although the European and ringlegged earwigs are susceptible to organochlorine insecticides, the striped earwig is not. It can be controlled with organophosphorus or carbamate insecticides, such as malathion, diazinon, and carbaryl. Propoxur was found to be a particularly toxic insecticide for Labidura riparia. The LC50 for propoxur was 0.04% compared with 0.13% for diazinon. However, treatments applied inside the house, as for cockroaches, did not control striped earwigs. They could be controlled by applying insecticide to the soil in areas 1 to 2 yd (1 to 2 m) wide around the perimeters of structures. Propoxur bait performed well in tests, but would probably have to be applied once a month (Clements and Kerr, 1969).
Cricket Species List
- Field Cricket, Gryllus assimilis
- House Cricket, Acheta domesticus (L.)
- Western Mole Cricket, Neocurtilia cultriger (Uhler)
- Southern Mole Cricket, Scapteriscus acletus Rehn and Hebard
- Camel Crickets:
- Ceuthophilus californianus Scudder
- Ceuthophilus pallidus Thomas
- Ceuthophilus maculatus (Harris)
- Pristoceuthophilus pacificus (Thomas)
- Greenhouse Stone Cricket, Tachycines asynamorus Adelung
- Jerusalem Cricket, Stenopelmatus fuscus Haldeman
The closely related crickets (Gryllidae) and katydids (Tettigoniidae) (order Orthoptera) share with the cicadas the honor of being the musicians of the insect world. The music of crickets and katydids is produced by the males with their stridulatory organs. These consist of a file and a scraper on each of the tegmina (forewings). The tegmina are moved back:and forth so that the files are rubbed against the scrapers. This causes a vibration of areas called "tympana," producing the chirping or ticking sound. Species of crickets and katydids, as well as cicadas, which belong to a different order (Homoptera), can be recognized by the differences in the sounds of their songs, and these differences have been responsible for the initial recognition by entomologists of many theretofore undescribed species. The females, which do not sing, are attracted to the "calling" sounds of the males, which are sensed or received by organs of hearing located at the bases of the tibiae of the forelegs. Although a cricket's song may seem pleasant outdoors, it is generally disliked within the house. The female cricket moves to locate the stridulating male, for which reason many more females than males are likely to be found. The males, after finding suitable locations, usually remain in them all their lives (Alexander, 1957).
Crickets and katydids both have long, filiform antennae. The tegmina of crickets lie flat on the back, but are bent down abruptly on the sides, and the tarsi are 3-segmented. The tegmina of katydids are held rooflike over the back, and the tarsi are 4-segmented.
Of the 2 groups, the occasional household pests are the crickets. Two species may be involved the field cricket, "Gryllus assimilis" (quotation marks are explained in the following text), and the house cricket, Acheta domesticus. In the western states, the field cricket is the principal pest. When their natural food supply of grasses dries up, crickets may migrate, and homes and other buildings may be invaded by thousands of these insects.
Multitudes can be attracted to lights and will sometimes cover streets and walks several inches deep (see under "Economic Importance"). They usually enter a building during the first cold days in the fall, through cracks and apertures such as around poorly fitted doors or loose basement windows. Some are carried in with firewood. Excessive rainfall may cause household or other building invasion.
Field Crickets, "Gryllus assimilis (F.)" (= Acheta)
Field crickets are indigenous to most of North, Central, and South America, and can be found almost everywhere except at high altitudes, in the far north, and in extremely moist situations. R. D. Alexander (correspondence) believes that there are about 25 species of Gryllus in the United States. Five of them are chiefly east of the Mississippi River, and 6 are chiefly in the Great Plains, Rocky Mountains, and southward. California has at least 10 species, including assimilis (F.) (only in the southern areas of the state), armatus Scudder, lineaticeps Stil, pennsylvanicus (Burmeister), veletis (Alexander and Bigelow), and 6 undescribed species. In the literature, however, field crickets have usually been included in a single, admittedly variable, species, "Gryllus assimilis (F.)," so for the sake of convenience, the name is retained here to represent the entire complex.
Description. In the United States, field crickets range in length from 13 to 28 mm, and from solid black to pale straw color. They have long, slender antennae, much longer than the body. The females have 3 conspicuous appendages extending from the tip of the abdomen, the middle one being the ovipositor (figure 359). The males may be distinguished by their having only 2 caudal appendages. Alexander (1957) recognized that, among field crickets, forms that were morphologically similar in different localities could be found in 3 types of habitats: "(1) large, light-colored forms in sandy areas (beaches, sand dunes, and deserts); (2) small, black forms in deciduous forests; and (3) forms intermediate between these two extremes in grassy and weedy areas, such as prairies, fields, pastures, roadsides, and lawns."
Life Cycle. Severin (1926) gave an account of the life cycle of "Gryllus assimilis" based on 12 years of investigation of the insect in South Dakota. He believed that there were 2 biological races in that state, one of which, probably less than 5% of the cricket population, overwinters as nymphs of usually the fifth and sixth instars, under leaves, trash, and other debris. They become adults during the latter part of May, reproduce during June, and die in July. The other race overwinters in the ground in the egg stage. They reach maturity during late July and early August. Many live out their life span, reproduce, and die by mid-September, but some live until they are destroyed by a heavy freeze. There is very little overlapping of living adults of the 2 races.
In the race that hibernates in the egg stage females begin to oviposit within 2 weeks after becoming adults, and continue until they die. They prefer to oviposit in soil that is firm, but soft enough to permit the ovipositor to enter readily. They prefer damp soil, such as that along ditches or at the bases of cracks in baked soil, or they will uncover damp soil by digging pits with the first 2 pairs of legs (Metcalf et al., 1962). The eggs are deposited 7 to 25 mm beneath the surface. They are laid singly, but 50 or more may be laid in an area about 5 cm square. A female normally lays 150 to 400 eggs. When first laid, they are light honey-yellow, and 2.8 to 3.2 mm long. After passing through the winter, they are cream-colored and slightly larger (Severin, 1926). According to Severin, field crickets passed through 8 or 9 instars. There was little difference in the period required by males and females for nymphal development, and it ranged from 82 to 93 days. In the Gulf states and the California deserts, "Gryllus assimilis" overwinters in nymphal instars, and is active throughout the year. There may be as many as 3 generations per year.
Economic Importance. The field cricket can destroy field crops such as alfalfa, alfalfa seed, cereals, and vegetable crops such as tomatoes, cucumbers, peas, beans, and strawberries. Great outbreaks of field crickets occasionally occur in several states simultaneously in the Midwest and South (Howell and Hensley, 1953; Hutchins and Langston, 1953). They sometimes invade towns and cities in great swarms. At such times, the sides of buildings may be covered with the insects, and it is necessary to sweep them from store fronts and sidewalks. They can become so abundant on streets and sidewalks under street lights that the slipperiness resulting from crushed crickets causes driving and walking to be hazardous. During such invasions of populated areas, the crickets, will also invade houses and other buildings. They have been reported to damage articles made of nylon, wool, plastic fabrics, and leather (Howell and Hensley, 1953), and "to eat holes in paper and rubber and in cotton, linen, woolen, or fur garments, either outdoors or indoors, especially when soiled with perspiration or foods" (Metcalf et al., 1962). The odor of dead crickets may be unbearable if they are not removed. During these invasions, cats may reject food and eat only crickets. The cats become emaciated and are subject to fits (R. N. Hawthorne, correspondence). Fortunately, field crickets cannot adapt themselves like house crickets to conditions within houses, and will die off by early winter (NPCA, 1968).
Folsom and Woke (1939) believed that during summers of extended drought, field crickets developed in large numbers when soils cracked extensively and provided shelter for the insects against weather and predators. Howell and Hensley (1953) observed that great swarms of crickets that invaded cities and towns were usually correlated with severe drought, followed by rainfall sufficient to produce food adequate for cricket development. However, in the desert valleys of southeastern California, where summer thunderstorms occasionally occur on days of especially high temperature, great swarms of crickets will invade towns on the same day as a thunderstorm takes place. This happens nearly every summer. Five mm of rain can trigger such an outbreak.
House Cricket, Acheta domesticus (L.)
Unlike field crickets, house crickets can maintain themselves indefinitely indoors. They deposit their eggs singly in dark places and crevices, such as behind baseboards, and can go through their entire life cycles within the building. They are normally found in warm, dark locations, hiding during the day but coming out at night, when their presence is indicated by their chirping.
Description. The adult averages about 20 mm long, and is light yellowish brown or strawcolored, with 3 dark bands on the head (figure 360). As with the field cricket, it has slender antennae that are longer than the body.
Life Cycle. Under laboratory conditions, the female lays an average of 728 eggs at 28° C (82° F), and there are 7 to 8 nymphal instars. The nymphal stage (over-all) requires, on the average, 55.8 days for males and 52.9 days for females. The preoviposition period averages 10 days, oviposition period 35 days, and postoviposition period 19 days (Ghouri and McFarlane, 1958). In the field, overwintering eggs generally hatch in late spring, and the adults appear in late summer, there being only 1 generation per year.
Economic Importance. During a 15-year period of investigation before 1935, the house cricket was more often encountered outdoors than indoors (Back, 1936). Wherever it had become a serious household pest in 35 cities and towns, the infested houses were located near an active city trash dump. In these dumps, the crickets were not seen during the day unless they were exposed by removing objects under which they were hiding. With the approach of darkness, they began to migrate, crawling or flying, particularly after city lights were turned on. They then appeared in large numbers on tree trunks, telephone or electric light poles, and on the sides of houses, sometimes entering second and third-story windows or skylights on the roof. During such infestations, one could scarcely move an article of furniture or other object in a house without uncovering crickets. Infestations tended to continue until the trash dumps or fills were covered over with earth.
In infestations such as those just described, all types of clothing are damaged. Large areas are eaten out of the fabric, rather than the small holes typical of clothes moth infestation. Heavy damage to wool, cotton, silk, synthetic fabrics, and even carpeting has often been reported (Back, 1936). Clothes stained with perspiration are particularly attractive to crickets.
In a controlled experiment with cotton and synthetic fabrics, house crickets caused severe damage to some synthetic fabrics and some damage to all of them. There was, greater damage to clean fabrics than to the same fabrics when stained with an animal fat collected from kitchen food preparation drippings and strained through an 80-mesh screen. Damage to the unstained acetate, viscose, and triacetate fabrics was extensive. There was slight damage to the polyester, nylon, and acrylic fabrics. Crickets preferred the same 3 fabrics as American cockroaches with which they were compared. There apparently was no damage to cotton fabrics (Finley et al., 1968).
Control of Field and House Crickets
A poison bran bait, with cane molasses as the attractant and sodium fluosilicate as the toxicant, gave good results against field crickets. Sodium fluoride was slightly less effective, and arsenicals were ineffective. A sodium fluosilicate bait was also recommended for control of the house cricket in city dumps (Back, 1936). Some authorities believe that to prevent crickets from entering houses, the bait should be placed under boxes, boards, and other objects under which crickets tend to hide during daylight hours. However, D. A. Reierson (personal communication) was able to stop the movement of field crickets toward a house by broadcasting a pound (0.45 kg) of a proprietary 2% propoxur bait in an adjacent field from which the crickets were coming. The bait was scattered mostly next to a block wall fence that the insects had to cross to reach the house. Many dead crickets were found in the treated areas for several days after the bait was applied. This house had been infested for several weeks, and cricket feeding scars were evident on carpets, draperies, and upholstered furniture. Poison bran bait with bloodmeal was found to be the most effective bait for field crickets in tests made in the Imperial Valley of California (R. N. Hawthorne, correspondence).
Mallis (1969) quoted D. E. Howell as stating that in 1954, a field cricket infestation in Stillwater, Oklahoma, was controlled with a 0.5% lindane spray. Four hours later, more than 75 cu m of crickets were swept up in the downtown areas of the city. In later tests, malathion, diazinon, and other organophosphorus insecticides were found to be even more effective than lindane.
Removal of ivy and shrubs from buildings is said to aid in cricket control. Openings in buildings, particularly at the thresholds of doorways, should be sealed. Residual sprays applied to baseboards, in closets, under stairways, and around fireplaces are said to be useful, keeping in mind that field crickets are usually restricted to basements and ground-floor levels, whereas house crickets may be found in any part of the house. Any insecticides and concentrations used for cockroaches are effective in cricket control. Insecticide dusts, such as Dri-die 67®, Drione®, 5% chlordane, or sodium fluoride are useful in enclosed spaces, such as attics, crawl spaces, wall voids, or behind baseboards. Kepone® pellets may be applied under drawers, sinks, and in other hiding places, as in cockroach control. Following a residual spray, a space spray or aerosol may be useful to drive many of the crickets out of hiding places and cause them to contact fresh residual deposits. In the southern states and the desert valleys of the Southwest, it is necessary to treat outdoors as well as in buildings. Some infestations of house crickets have been controlled by covering the city dump with earth.
There are other crickets, besides the field and house crickets, that may occasionally invade homes and other buildings and become minor pests. Among them are the mole crickets. They belong in the family Gryllotalpidae, which was once considered to be a subfamily of the Gryllidae in which the crickets already discussed belong. As the common name implies, they resemble miniature moles because of their large, shovel-like fore tibiae, adapted for digging, and in their burrowing habits. Mole crickets are usually brown or black, and 25 to 50 mm long. The tegmina are short, and the second pair of wings protrude like tails. They are weak fliers, and seldom attempt to fly. They usually have no stridulatory organs, and do not jump. When crawling, the forelegs are held forward and off the ground.
Habits. Although mole crickets spend most of their time in permanent burrows several inches deep in the soil, they may come to the surface when the soil has become wet, and particularly at night when temperatures are above 70 °F (21 °C). They will then make temporary burrows in the upper stratum (2.5 or 5 cm) of the soil, and can cause serious damage to lawns and golf courses by their burrowing. They are among the major pests of turf in Florida and some other southeastern states. They also crawl about on the surface and feed on ripening strawberries and the fruits of other crops if they touch the ground. They occasionally enter basements of buildings (Wisecup and Hayslip, 1943; Short, 1973).
Neocurtilia cultriger (Uhler) (= Gryllotalpa)
This is the only western mole cricket. It occurs in California, Arizona, New Mexico, and Texas. It is about 25 mm long, cinnamon brown, with dark marks at the bases of the legs, and has wide tegmina that cover the 4 basal abdominal segments.
Southern Mole Cricket, Scapteriscus acletus Rehn and Hebard; and Changa, S. vicinus Scudder
In the southern states, these 2 species of mole crickets are often found in sandy soils. They are brown, and about 40 mm long. They pass the winter in the soil as nymphs or adults, burrowing deeper during cold weather. In spring and early summer, the females oviposit in cells they construct in the soil from 3 to 10 in. (7.5 to 25 cm) below the surface, laying about 35 eggs per cell. These hatch in 10 to 40 days, depending on the temperature. There is only 1 generation per year.
Control of Mole Crickets
For many years, a sodium fluosilicate-wheat bran bait was used for the control of mole crickets in Florida (Wisecup and Hayslip, 1943). More recently, chlorpyrifos and propoxur baits have been recommended, and were found to be equally effective when applied at 1 lb/acre (1.135 kg/ hectare). With a given quantity of toxicant per unit area, a 0.5% bait gives better results than a more concentrated one because of more thorough distribution with larger quantities of bait. Chlordane spray and granules, carbofuran granules, and propoxur spray were also effective. Better controls with sprays and granules in the spring and better controls with baits in the summer and fall were observed. Good control could be obtained only when night temperatures were above 60 °F (16 °C) and when the soil was moist (Short, 1973).
Camel crickets (Gryllacrididae), also called stone or cave crickets, are wingless, have very long antennae, and long hind legs with large femora adapted for jumping. The large head is bent downward between the forelegs and the back is arched, giving these insects a humpbacked appearance. Camel crickets are nocturnal, and live in caves, wells, cracks or holes in the ground, in rotten logs or stumps, or under damp leaves or stones in cool, dark situations. Most species are found irn woodland areas, but others occur in grassland or even in desert regions. These dig holes in the ground or inhabit the burrows of larger animals or other cavities, from which they emerge at night. Camel crickets have no "song" to attract attention, are somberly colored, spend the day in close concealment, and are immobile in the presence of strong light. It is not surprising that they are not well known to the layman or even to the professional entomologist. Despite the common name, "cave cricket," only 1 species of Ceuthophilus found in Carlsbad Caverns is an obligatory cavernicole or troglobiont; other species are merely troglophiles, and may be found in any humid and concealed situation, sometimes invading damp cellars (Hubbell, 1936). They overwinter as adults or nymphs, oviposit in the spring, and the eggs hatch during April.
Crampton (1923) observed a species of Ceuthophilus crawling about in the open privies in a mountain camp in Massachusetts and the same species crawling over food on pantry shelves. He was surprised to find no reference to these insects as vectors of pathogenic organisms.
Ceuthophilus californianus Scudder
Most camel crickets are in this genus. Hubbell (1936) wrote a massive monographic revision of the genus, which contains many species, and is well represented in the western United States. Ceuthophilus californianus (figure 361, top) is uniformly pale brown, except for the darker chestnut-brown dorsal bands, and is 15 to 25 mm long. It is most commonly seen at the entrances of gopher holes on overcast spring days, and may also be found in soil or under stones or logs. This species occurs only in California, inhabiting the arid grasslands of the central valley and coastal strip. It is replaced by C. hesperus Hubbell from Los Angeles southward (Hubbell, 1936).
Ceuthophilus pallidus Thomas
This species occurs over a very large area in the Great Plains, from southern Canada to Texas, and in the dry grasslands of the southwestern United States and northern Mexico (Hubbell, 1936). It is often found indoors in summer, and was observed eating holes in lace curtains in southern New Mexico.
Ceuthophilus maculatus (Harris)
This is another related species that has shown a preference for textiles. Townsend (1893) reported that it was found feeding on clothes hung out on a line after washing. It occurs in Colorado at high altitudes, from 7,000 to 10,000 ft (2,100 to 3,000 M).
Pristoceuthophilus pacificus (Thomas)
This genus occurs along the Pacific Coast, from British Columbia to Mexico. Most species have dorsal specializations on the males' abdomens, such as spines, tubercles, and peculiar glandular structures. Some species also have strangely formed hind tibiae, usually found only in the males (Caudell, 1916). The species illustrated here is P. pacificus (figure 361, bottom), and was taken in the author's laboratory in Los Angeles.
Greenhouse Stone Cricket, Tachycines asynamorus Adelung
This is probably the best-known camel cricket in the United States. It is reported mainly as a pest in greenhouses in Europe and in the United States as far west as Colorado. A. B. Gurney (correspondence) believes that in Washington, D.C., this insect migrates from sewer outlets into homes. People who find it in their basements generally describe it as a "large, spiderlike creature, without wings, that jumps very high when disturbed."
Jerusalem Cricket, Stenopelmatus fuscus Haldeman
The Jerusalem cricket (family Stenopelmatidae) is worthy of consideraion because of the great fascination and sometimes fear that it evokes on the part of the layman who may occasionally see one in his yard or garden, or even in his home. It occurs west of the Rocky Mountains and in British Columbia and Mexico. In the latter country, it is called nina de la tierra (child of the earth) because its large, round, naked head with 2 beadlike black eyes gives it a fancied resemblance to a miniature child. The southwestern Indians once feared it, and called it "child of the desert." In California, it is commonly called "potato bug" because it occasionally feeds on potatoes and other root crops while still in the soil (Davis, 1927). When a large planting of potatoes near El Monte, California, failed to sprout, every hill that was uncovered and examined was found to contain several Jerusalem crickets (Baker, 1971). However, such extensive damage by these insects is rare.
At Los Angeles, we receive many telephone calls concerning this strange-looking creature, despite its relative scarcity. It is one of the few insects that the layman adequately describes. Common questions are, "Is it dangerous?" and "What shall I feed it?" The Jerusalem cricket is harmless, although when cornered it may rise on its hind legs, facing the annoyer, and jump at the attacker if teased sufficiently. Its powerful mandibles can inflict a minor, nonvenomous wound when it is handled carelessly. It may also make a sound like 2 pieces of sandpaper rubbed together by scraping the hind legs against the tough plates on the sides of the abdomen. These insects are becoming more prevalent in California, and are entering houses in increasing numbers, if one may judge by the inquiries received from homeowners. They have even been found in third-floor apartments.
Description. Stenopelmatus fuscus (figure 362) is the largest member of the genus, being 30 to 50 mm long; an occasional specimen may be larger. The head, thorax, and legs are shining, pale amber-yellow to brownish. There is not the slightest vestige of wings. Dorsally, the abdomen is shining amber-brown, with wide, almost black, bands across the anterior margins of the segments, and ventrally it is pale amber. The long hind tibiae have 2 or 3 outer and 4 or 5 inner spines. The male has a more massive head and thorax and a smaller abdomen than the female.
Biology and Habits. Jerusalem crickets are nocturnal and are not often seen, but in winter, spring, and early summer they may be found under rocks in open, grassy pasture land, or may occasionally be seen crawling about in the evening. Baker (1971) described the interesting trail left by one of these insects in soft dirt: "A snakelike, continuous track made by the dragged abdomen, with a series of cleatlike tracks on either side, made by the legs. By following these tracks on a warm evening, one may sometimes find the insect searching for food." In California, they estivate in the fall, and can then be obtained only by digging in manure heaps and damp places. In captivity, they will eat bread, grass roots, vegetables, and fruit, but prefer any kind of meat or small insects. After copulation, the females may kill and eat the males.
The Jerusalem cricket burrows in the soil, but unlike the mole cricket, which burrows with specialized fore tibiae, the Stenopelmatus does its digging mainly with its large and heavily sclerotized head. The closed mandibles are used as a hoe, scraping the earth back and underneath. In southern California, they have been found in moist, light, loamy soil or in deep cracks in adobe soil. The females make nest burrows beneath rocks or boards that extend downward for 6 to 1 0 in. (15 to 25 cm), then turn sharply to one side and end in an enlarged chamber, often lined with a paperlike substance, in which the eggs are laid. The eggs. are whitish, oval, and about 3 mm in diameter (Davis, 1927; Baker, 1971).
- Boxelder Bug, Leptocoris trivittatus (Say)
- Weed Bug, Arhyssus crassus Harris (Rhopalidae)
- Grass Bug, Nysius raphanus Howard (Lygacidae)
The true bugs (Hemiptera-Heteroptera) have the forewings thickened in the basal half, while the apical half is thin and membranous. They are sucking insects, and are common pests of vegetation. The species described here are those that sometimes leave vegetation and migrate into near-by houses in large numbers, if one may judge by the inquiries received from homeowners.
Boxelder Bug, Leptocoris trivittatus (Say); and Western Boxelder Bug, L. rubrolineatus Barber (Rhopalidae)
Boxelder bugs are widely distributed throughout the United States, particularly where pistillate or seedbearing boxelder trees (Acer negundo) are found. Leptocoris trivittatus ranges throughout most of the United States and as far west as eastern Nevada. The western boxelder bug, L. rubrolineatus, which is similar in appearance and habits' is the species occurring in California and Oregon. Boxelder bugs feed on seeds, foliage, and tender twigs. They do not attack the male tree. They also occur to a lesser extent on maple and ash, and will occasionally feed on the young fruits of crops such as apples, pears, cherries, peaches, plums, and grapes, their punctures causing the fruit to be deformed. The adults spend the winter in dry, sheltered places - hollow tree trunks, barns or other outbuildings, and even in homes. They may swarm in large numbers on warm, sunny days, and residences not already chosen by the bugs for hibernation can be invaded during these flight periods. The mere presence of large numbers of boxelder bugs in the home is, of course, a nuisance, and in addition they can discolor curtains, furnishings, and clothing by spotting them with their excrement. When crushed or handled roughly, the bugs produce a strong, disagreeable odor. They sometimes bite people, and some difficulty has been experienced in healing the bites (Knowlton, 1947; Brannon, 1961).
Description. The adults of Leptocoris trivittatus average about 12 mm long, are rather flat and narrow, gray-brown to black, and have red margins on the basal halves of the wings. The adults of L. rubrolineatus are a little shorter and narrower than those of L. trivittatus. They average about 10 mm long, and the basal halves of the wings have not only red margins, but also 3 longitudinal red stripes (plate VIII, 8). The nymphs are bright red at first, but become marked with black when about half grown.
Biology. In the spring, the overwintering females lay their minute, red eggs in cracks and crevices of the bark of the host plant. The eggs hatch in about 2 weeks, close to the time when the new leaves are about to appear. There are 5 nymphal instars.
In the warmer regions of the United States, there are 2 generations per year. In California, all stages mass-migrate periodically, covering the ground, shrubs, and fences. What motivates the bugs to migrate is not known.
Control of Boxelder Bugs
An obvious way to avoid infestations by this pest in residential properties is to get rid of near-by female boxelder trees. Some city ordinances proclaim the female trees to be nuisances, and they can be removed at city expense. If this species is to be planted as an ornamental or shade tree, male trees should be purchased from the nursery. They are propagated by cuttings from staminate trees.
Chemical control can best be obtained by spraying the nymphs on the host trees before the adults have had a chance to migrate. Power spray equipment is usually required. Many residual insecticides have been successfully used. Malathion is suggested for those interested in an insecticide of minimal mammalian toxicity and with a brief residual life. One spray on the ground, tree trunks, and fences will usually control the pests, despite the brief residual life of malathion (R. N. Hawthorne, correspondence). In the home, the insects can be collected with a tank-type vacuum cleaner and then destroyed. Good control has also been obtained by applying aerosols containing TDE plus synergized pyrethrins. Before the advent of organochlorine insecticides, ordinary pyrethrin fly sprays were recommended for indoor treatment of boxelder bugs (Craighead, 1950). When referring to conditions in the eastern United States, Vasvary (1965) suggested, for indoor infestations 2% chlordane in deodorized kerosene, sprayed or painted into cracks and on surfaces where boxelder bugs were hiding, paying particular attention to attics, especially close to the eaves, and to the cellars near foundation walls.
Weed Bug, Arhyssus crassus Harris (Rhopalidae)
The weed bug is a house pest of considerable importance throughout California, particularly in new subdivisions and in areas adjacent to uncultivated fields, ditch banks, or levees. As much as a liter of these bugs has been collected in some houses. The adults (figure 363) are uniformly brown, and about 9 mm long. A favored host is the yellow star thistle, Centaurea solstitialis, but the insects occur on many other plants. They migrate into houses in large numbers when their native habitats are disturbed or when the weeds they normally infest begin to dry in summer. They are attracted to light-colored buildings more than to those of darker colors, and tend to crawl through any openings that they find under windows or doors. They stain draperies and rugs with their excrement, which is practically impossible to remove by the usual cleaning operations. The bugs themselves have an objectionable odor.
Control of Weed Bugs
There is no control measure that is effective after the bugs have moved into populated areas and become household pests. Even when they are sprayed before entering a house, they are still able to go inside, and then die. Their control in the form of disking or spraying, needs to be applied in the originally infested grasslands. Carbaryl (Sevin®) is an effective insecticide (R. N. Hawthorne, correspondence).
Grass Bug, Nysius raphanus Howard (Lygacidae)
This bug feeds principally on grass, in contrast to Arhyssus crassus, which feeds mainly on weeds. As a house pest, this species is most troublesome in new subdivisions. It is a very small bug, about 3 mm long, with a dark body but with whitish, translucent wings that give the insect a generally grayish appearance (figure 364). It is rather inconspicuous until it becomes very numerous. In rural areas, Nysius raphanus usually occurs in pasture lands, but in cities and towns, it is found in vacant lots and along fences. When the wild grass becomes dry, or when it is mowed or burned, the adults and nymphs migrate, covering fences and sides of houses, finally invading the buildings in great numbers. Once an infestation gets under way, it takes about 5 years for the bugs to disappear (R. N. Hawthorne, correspondence).
- Tule Beetle, Agonum maculicolle Dejean
- Stenolophus lineola F.
- Stink Beetle, Nomius pygaemus (Dejean)
- Elm Leaf Beetle, Pyrrhalta luteola (Müller)
- Black Vine Weevil, Brachyrhinus sulcatus (F.)
- Cribrate Weevil, B. cribricollis (Gyllenhal)
- Egyptian Alfalfa Weevil, Hypera brunneipennis (Boheman)
- Strawberry Root Weevils, Brachyrhinus ovatus (L.) and Sciaphilus muricatus (F.)
Certain beetles (order Coleoptera) may invade residences and other buildings and become troublesome seasonal pests in some areas.
Ground Beetles (Carabidae)
The ground beetles: are predaceous on many injurious insects and consequently are normally beneficial to man, but they are nevertheless considered to be pests when they enter buildings.
Tule Beetle, Agonum maculicolle Dejean
In the central valleys of California, the tule beetle is the most troublesome carabid. It breeds in the tules or marshlands along rivers, and appears in great numbers at dusk following fall rains. It may enter houses, and is particularly annoying because of its offensive odor, which is also a characteristic of various other carabids. Tule beetles usually invade a house from the direction of their breeding grounds. According to C. S. Papp, this or a closely similar species invades houses in southern California. The adults are almost 10 mm long. The pronotum and elytra are dark brown, with light-brown or tan margins (plate VIII, 8). Insecticides do not seem to be able to kill tule beetles quickly enough to keep them from crawling into a building before they die. A successful control measure has been to install an electric light above a container filled with water, with detergent added, about 50 ft (15 m) from the house. The beetles attracted to the light, fall into the water and drown.
Other Ground Beetles
Stenolophus (Agonoderus) lineola F. is a common beetle throughout the United States. It sometimes becomes a nuisance by invading houses after being attracted to porch lights (Papp, 1960).
Nomius pygmaeus (Dejean), the stink beetle, occasionally invades houses in the western states. It has a particularly offensive odor that is retained for weeks on household articles upon which the beetle has crawled (Hinton, 1945). Its presence in towns has been associated with near-by forest fires, the insects apparently having been driven out of the forests by smoke (Spencer, 1942). The control measure just suggested for the tule beetle should also be effective against other carabids that have similar habits.
Darkling Ground Beetles (Tenebrionidae)
In this family are some small black or brown species that may invade the home, particularly when they migrate into green areas from the surrounding hills after the native vegetation dries up following the last spring rains in California. In the southern part of the state, Metoponium abnorme (LeConte), Coniontis subpubescens LeConte (figure 365), C. parviceps Casey, and species of Blapstinus are examples of tenebrionids that feed on the buds and foliage of plants such as young avocado trees, grapevines, and seedling tomatoes, and may also find their way into houses in large numbers. (Figure 365.)
Elm Leaf Beetle, Pyrrhalta luteola (Müller) [= Galerucella xanthomelaena (Schrank)] (Chrysomelidae)
This important elm-tree pest was introduced from Europe about 1834, and is widely distributed in the United States. In California, it was first found in Fresno in 1924. The adults are 5 to 6 mm long and yellowish to dullish green, with an indistinct black stripe along each side. The orange-yellow, spindleshaped eggs are laid on end in groups of 5 to 25 on the undersides of leaves. The yellow to black larvae, about 12 mm long, skeletonize the leaves. The pupae, about 6 mm long, are bright orange-yellow, and have black bristles. The adults may enter dwellings in late summer or fall to hibernate behind curtains, between books, beneath carpets, and in other protected places. They again become active in the spring, and crawl throughout the house. There are 2 to 5 generations per year, depending on climatic conditions. These insects may be killed within the home with the usual household insecticides, but control is difficult because the infestation is being continually renewed. For outdoor control, infested trees can be sprayed with carbaryl 50%, wettable powder, using a 2 lb per 100 gal (0.91 kg per 378 L) of water (Koehler et al., 1970; Cress, 1971).
The weevils comprise a very large family of beetles, characterized by the prolongation of the head into a distinct snout with biting mouthparts at its tip. All weevils are phytophagous, both as larvae and as adults.
Black Vine Weevil, Brachyrhinus sulcatus (F.); and Cribrate Weevil, B. cribricollis (Gyllenhal)
These weevils belong in a subfamily (Otiorhynchinae) in which the snout is short and wide. They do not fly. The black vine weevil (figure 366-67, A) is about 8.5 mm long and brownish black. There are small patches of golden scales scattered about on the elytra. The pronotum is densely covered with tubercles, and the elytra are coarsely punctured and striate. The adults are nocturnal, and feed on many plants. The white, legless larvae live in the soil and feed on plant roots, and are 10 mm long when mature. The cribrate weevil is 6 mm long, and varies from black to brown (figure 366-67, B). This beetle was first noticed in Los Angeles County, California, in 1928, and has since spread over much of the state. Weevils of this genus were accidentally introduced into North America, and have subsequently been widely distributed on nursery stock. They are often found on hedges and other dooryard plants, sometimes nearly defoliating them before the pests are noticed. When weevil populations become excessive, or when conditions become unfavorable for them, they tend to seek shelter by migrating into residences (R. N. Hawthorne, correspondence).
Egyptian Alfalfa Weevil, Hypera brunneipennis (Boheman)
This important alfalfa and clover pest is another imported species. It was discovered near Yuma, Arizona, in 1939, and was confined to the desert areas of Imperial County, California, for many years, but extended its range to San Diego County in 1951 and now occurs over much of the state.
The Egyptian alfalfa weevil (figure 366-67, C) resembles the more widely distributed alfalfa weevil, H. postica (Gyllenhal), in appearance, life history, and habits. The adult is about 5 mm long, grayish brown to nearly black, with short, grayish hairs. It belongs in a subfamily (Curculi-oninae) in which the beak is long and slender. In H. brunneipennis, the beak projects downward from the front of the head and is about half the length of the thorax. The adults hibernate about the crowns of alfalfa (or clover) plants or under leaves and rubbish, then feed a few days and mate. The females lay as many as 40 oval, yellowish eggs in cavities they make with their beaks in alfalfa stems, and may lay from 400 to 600 eggs each during the spring. The green larvae, with a prominent dorsal stripe, feed on alfalfa and become mature about the time the first crop is cut. They then spin a netlike, nearly spherical, cocoon in the ground and pupate, emerging as adults in about 10 days. The adults also feed on alfalfa plants, and may occur in enormous numbers.
The weevils tend to migrate from alfalfa fields to marginal areas, tree rows, fence rows, buildings, and sheltered locations, and sometimes invade residences. Entomologists of the California Department of Agriculture became aware of over 30 invasions of houses by alfalfa weevils in a single month (November, 1971) from specimens sent to their taxonomists by agricultural commissioners from all areas of the state. Probably many other such invasions were not reported. The beetles cause no spotting problem such as caused by weed bugs, and leave no disagreeable odor as do the weed bugs and tule beetles, but nevertheless they are pests merely because of their unwanted presence in the home.
Strawberry Root Weevils, Brachyrhinus ovatus (L.) and Sciaphilus muricatus (F.)
In some parts of the country, the strawberry root weevil, Brachyrhinus ovatus, can become a pest in the spring and fall. It is 6 or 7 mm long and blackish brown. The larvae feed on the small roots of wild and cultivated strawberries, brambles and evergreens such as pine and yew. Root weevils sometimes invade a home in enormous numbers. The adults will then be found singly or in groups in such places as bathtubs and cupboards, or even crawling on the ceiling. Another curculionid, Sciaphilus muricatus, has the same habits. It is about a fourth longer than B. ovatus, and is more slender. The body is tannish gray, the head tending to be slightly lighter.
Destruction of wild strawberries in the vicinity of houses helps to control both these species. Also, thorough spraying of foundations with wettable powders of chlordane or lindane, or applying them as dusts, has proved to be useful in control. The surrounding area within 10 ft (3 m) of the foundation should also be treated. The treatments may need to be repeated in about 3 weeks and possibly again later. If the beetles invade the home, gathering them up with a vacuum cleaner seems to be the best procedure (Cress, 1971).
INSECTS FEEDING IN BEE COMBS IN BUILDINGS
Certain insects are attracted to weakened, abandoned, or fumigated honey bee co!onies in inaccessible parts of buildings, feeding on wax, honey, or the waste products in the comb. They can find their way into occupied areas of the buildings and become serious pests. Some of these insects (ants, carpet beetles, and cockroaches) are discussed elsewhere in this book. The greater wax moth and a soldier fly are discussed in this section.
Greater Wax Moth, Galleria mellonella (L.) (Pyralidae)
As just outlined, combs of honey bee colonies in wall voids, attics, and chimneys are often infested by the greater wax moth. The moths and their larvae may then find their way to the living space of the house and become pests. The adults are gray or pale brown, marked with black. "Bumps" on the forewings, which can be seen along the upper margins in figure 368, are composed of tufts of wing scales that are much longer and broader than those covering the rest of the wing areas. The females are about 20 mm long. The males are somewhat smaller, and do not have palpi. The larvae are white when first hatched, but in later instars they may vary from white to yellow, with brown or black heads and prothoracic shields, or their backs may be largely black. The larvae destroy combs by burrowing through the cells. They feed on pollen and waste materials, and construct silken tunnels as they make their way through a comb. If they become pests in the living space of the infested house, the comb should be removed, if possible, or it should at least be sprayed or dusted with any available household insecticide.
A Soldier Fly, Hermetia illucens (L.) (Stratiomyidae)
This widespread soldier fly occasionally becomes a house pest after honey bee colonies have been exterminated in wall voids or other hard-to-reach places. The adult (figure 369) is about 15 mm long and black, except for a large, translucent area on the second tergum and white areas on the tibiae. The larvae feed on waste materials in bee combs, and can become very numerous if the wax moth does not reach the combs first. The larvae sometimes find their way into the living space of the home, and the conspicuous pupal cases (shown in the figure) have been found in carpeting. According to James (1960), the adults may be attracted to light, but do not seem to molest food. They are sluggish until induced to fly. Outdoors, they visit excrement, but usually not flowers. James recorded this species as breeding in decaying or putrefying vegetable or other organic matter, including human excrement, but stated that it might at times be a predator in such media. He also had records of its occurrences in decomposing wet rice, soybeans, fruits, vegetables, ketchup, animal cadavers, and in waste materials found in beehives. This species has also been recorded as causing intestinal myiasis in man.
SWIMMING POOL PESTS
Arthropods can be problems in swimming pools, even those that are well cared for, because of their tendency to fall into the water and be trapped there. If the lawn and surrounding areas of shrubbery have an abundance of leaf litter, humus, or other organic material, and are kept damp by watering or rains, infestations of sowbugs, pillbugs, millipedes, or springtails often develop. (Controls for such arthropods are discussed in chapter 10.) Earthworms can also be problems. These and other pests may fall into the pool while crawling about. Many moths, beetles, and leafhoppers may accidentally fall in after being attracted to lights in and around the pool. Bees and wasps are often trapped in pools when they seek water. If swimming pools are not properly cared for, mosquitoes and midges can breed in the water. In areas near lakes, ponds, or streams, aquatic bugs and beetles often fly about in search of other water habitats, and are attracted to swimming pool lights. Among the bugs are the backswimmers (Notonectidae), which can use their sharp beaks to bite with an effect similar to that of a bee sting. Among the water scavenger beetles (Hydrophilidae) is a small, black, shining species, Tropisternus californicus (LeConte), the adults of which sometimes bite bathers in swimming pools in southern California (Essig, 1926). Mallis (1973) received some larvae of an unidentified species of Tropisternus in Pennsylvania, along with some blue plastic pool-liner material showing tiny holes. The owner of the pool said the holes were made by the larvae, which have long, sharp jaws.
Control of Swimming Pool Pests
Dip nets can be used to skim insects off the surface of the water. Pool skimmers usually do an adequate job of pest removal if they are used frequently. Pools left unused or that are not maintained for extended periods should be drained. Lights near pools should be used as sparingly as possible, particularly on warm nights. Lighting installed 20 to 30 ft (6 to 9 m) from a pool helps to keep attracted insects away from it. Also, yellow lights are less attractive to insects than white ones. Shrubbery and grass should be kept well trimmed, to reduce harborage and breeding areas for insects and other arthropods. Although insecticides should not be applied in the pool, a light malathion spray can be used advantageously on surrounding grass and other vegetation. During pool parties on hot summer nights, a 0.1% pyrethrin aerosol or mist applied around lights may provide temporary relief (Rachesky, 1973).
INSECTS IN MAUSOLEUMS AND CEMETERIES
Pest problems in mausoleums are apparently universal. The author and his co-workers have been asked to suggest means of controlling them on many occasions, and have often collected mausoleum-infesting insects and tested control measures. In any part of a mausoleum, small flies and midges, including mosquitoes, breed in the water or the slime remaining after the water evaporates from the numerous flower vases. A phorid fly, Megaselia scalaris, has been the species collected in largest numbers. Phorids are known to feed principally on decayed vegetab!e matter, such as might be expected where leaves or petals have remained in water for long periods. Insect infestations from this source have noticeably decreased when artificial flowers have been substituted.
In the areas containing the crypts, some kinds of mycetophilids feed on the fungi at imperfect seals on the outsides of the concrete shutters while the crypts are damp inside. (See the detailed discussion of fungus gnats in chapter 10.) Certain common species of beetles may sometimes be seen in the hallways.
The insect species that were collected during the foregoing investigations were as follows:
Megaselia scalaris (Loew)
Dohrniphora cornuta (Bigot)
- Chloropidae Oscinella frit (L.)
Pelomyia coronata (Loew)
Mycetophila fungorum (De Geer) (= punctata Meigen)
Necrobia rufipes (De Geer) (plate IV, 3; figure 189)
Necrobia ruficollis (F.) (figure 189)
Alphitobius diaperinus (Panzer) (figure 182)
Alphitobius piceus (Olivier)
In cemeteries, mosquitoes, particularly such species as Culex pipiens, C. pipiens quinquefasciatus, and Culiseta incidens, can breed outdoors in large numbers in the flower receptacles when water is left standing in them too long. Cemeteries have occasionally been sources of the yellowfever mosquito, Aedes aegypti, in southern states. Such species as Aedes sierrensis and Ae. triseriatus can breed in treeholes of shade trees if they are not sealed or filled with sand. The sources of these mosquitoes are often difficult to find (Aarons, 1948; Shanafelt, 1969). In the Orange County (California) Mosquito-Abatement District, in cemeteries where all containers are turned upside down when flowers are removed, mosquito production is negligible. In others, an average of 21 % of the flower containers have contained mosquito larvae. Containers located in areas shaded from afternoon sunshine were the ones that most often harbored the larvae (Shanafelt, 1969).
Control of Mausoleum Pests
The number of Diptera in mausoleum halls can be reduced by not allowing water to remain in flower vases too long (some midges develop from egg to adult in 10 days), and by making sure that no damp organic matter remains in the bottoms of the vases when they are refilled. Flies and beetles can be controlled by the use of insecticides applied with foggers or mist blowers, as described in chapter 3. Figure 370 shows a vapor generator by means of which lindane vapor was blown from the roof of a mausoleum down through the vent pipes in order to treat the crypts.
Miscellaneous Species List
- Amphipods, Talitroides sylvaticus (Haswell) (Talitridae)
- Greater Wax Moth, Galleria mellonella (L.) (Pyralidae)
- Soldier Fly, Hermetia illucens (L.) (Stratiomydae)
Fig. 351. Common slugs. A and B, gray garden dug, Deroceras reticulatum, C and D, banded slug, Lehmannia poirieri; E and F, greenhouse slug, Mitax gagates. Note the "extended" and "contracted' positions shown for each species.
Fig. 352. European brown snail, Helix aspersa.
Fig. 353. Snail eggs in a nest in damp soil. (From Basinger, 1931.)
Fig. 354. An amphipod, Tatitroides sylvaticus, that sometimes invades houses.
Fig. 355. Clover mite, Bryobia praetiosa.
Fig. 356. European earwig, Forficula auricularia. Female (left); short-forceps-type male; long-forceps-type male.
Fig. 357. European earwig, Forficula auricularia, and newly hatched nymphs in subterranean nest. An example of maternal care for the young among insects. (From Fulton, 1924a)
Fig. 358. Forceps of 3 species of earwigs. A, Labidura riparia (male, large type); B, Labidura riparia (male, small type); C, Labidura riparia (female); D, Euborellia annulipes (male); E, Euborellia annulipes (female); F, Forficula auricularia (male, short type); G, Forficula auricularia (female); H, F. auricularia (male, long type).
Fig. 359. Field cricket, "Gryllus assimilis."
Fig. 360. House cricket, Acheta domesticus.
Fig. 361. Two California camel crickets. Top, Ceuthophilus californianus; bottom, Pristoceuthophilus pacificus (adult male).
Fig. 362. Jerusalem cricket, Stenopelmatus fuscus
Fig. 363. Weed bug, Arhyssus crassus.
Fig. 364. Grass bug, Nysius raphanus.
Fig. 365. Darkling ground beetle, Coniontis subpubescens.
Fig. 366-67. Some crop pests that can invade the home. A, black vine weevil, Brachyrhinus sulcatus; B, cribrate .weevil, Brachyrhinus cribricollis, C, Egyptian alfalfa weevil, Hypera brunneipennis.
Fig. 368. Greater wax moth, Galleria mellonella, adult and larva.
Fig. 369. A stratiomyid fly, Hermetia illucens, adult and larva.
Fig. 370. Applying lindane vapor through a vent pipe of a mausoleum with a vapor generator.