Silverfish & Firebrats

August 15, 2009

SILVERFISH AND their heat-loving firebrat cousins attract surprisingly little research interest despite being major worldwide pests and chewing up rare book and paper collections along with food and textiles. But University of California, Riverside, entomologists are developing a renown for venturing into overlooked urban and domestic pest control realms. For her UCR Masters thesis, Mirtza Millard, an accomplished SciFi and Fantasy book illustrator, followed in the 17th-century footsteps of English microscope pioneer Robert Hooke. Hooke’s 1665 book Micrographia featured a lavishly illustrated chapter titled “To the small Silvery Bookworm.”

Millard, who is leaving behind Riverside firebrats and silverfish to study Texas ants, recommends baiting and trapping strategies rather than conventional pesticide sprays. Though pyrethroid and diatomaceous earth insecticides are often helpful, silverfish and firebrats may be repelled and go into hiding in cracks and crevices when surfaces are sprayed with conventional pesticides.

Fipronil, carbaryl or avermectin formulated into egg noodle and dog food baits work well against firebrats in lab tests; boric acid, indoxacarb and imidacloprid were not so effective. Conventional ant and cockroach baits (e.g. hydramethylnon) may be tasted (scraped on the outside), but are ineffective because they are not eaten. At UCR, Millard found that small particle (0.25-0.4 mm) baits made from grinding up high-protein egg noodles worked better than large particle and starchier baits.

Millard traps these wingless, crawling insects in small glass jars ringed with a sticky surface on the outside to make it easy for the pests to crawl inside. Once over the top of the jar, the insects lack wings to fly and cannot crawl out over the steep slick glass surface. It is similar to when silverfish seeking moisture and humidity get trapped in bathtubs and sinks and futilely try to crawl out.

Jar traps are best placed near cracks and crevices and in corners near foraging sites. It takes trial and error to master trap placement and figure out foraging sites. So try placing the small glass jar traps in different corners and near cracks and crevices until the best trap placement is learned. Numbers trapped may be small, as the insects cluster together mainly to mate, lay eggs and keep warm (via body heat) when it is cold.