Dr. Dong Hwan Choe’s research at UC Riverside found that some ant pesticides dramatically alter ants’ behavior before killing them. Thiamethoxam, a nicotine-like insecticide, makes Argentine ants unusually active and causes them to wander away from their nests. Boric acid has the opposite effect, causing ants to stop foraging and gather inside their nests, often near water. In laboratory tests, thiamethoxam killed nearly all worker ants within about a week, while boric acid killed about 90% within two weeks, but neither necessarily eliminates the queen. The findings could help homeowners and pest-control professionals understand unusual ant behavior after treatment and improve the effectiveness of ant baits.