Thanks to Wizzie Brown for alerting me to the recent, very cool video on cockroaches by NPR’s Science Friday. Like cats that lick their feet and fur, cockroaches continually groom their feet and antennae. I’ve watched cockroaches groom themselves, but never in magnified HD with a lucid narration by North Carolina State University entomologist Coby Schal. Dr. Schal reports on recent research by his laboratory to answer the question about why cockroaches groom, and he’s well worth listening to.
One thing the video does not mention is that we take advantage of this grooming behavior in pest control when we use certain insecticides. Boric acid is a relatively low risk pesticide that can be used around the home. Boric acid, it turns out, is ONLY toxic to insects (and coincidentally, people) when it’s ingested. When we apply boric acid as a dust, and a cockroach walks through the dust layer, a small amount of the insecticide is picked up on the roach’s feet, body and antennae. It’s because of the grooming behavior documented so elegantly in this video, that the cockroach is poisoned by such dusts. This may also be the case with other insecticides and other insect species, according to the news release by North Carolina State.
One caveat about using boric acid in the kitchen–don’t use too much. Cockroaches avoid heavy deposits of any dust, including boric acid. They are not repelled, however, by light dust deposits of boric acid. So if you use boric acid, take it easy. You should not be able to see more than the slightest dusting of white residue after an effective application of boric acid.