Iowa Insect Information Notes

Silverfish and Firebrats

Silverfish and Firebrats

Silverfish and firebrats are wingless, flat insects with two long, slender antennae on the front and three long, slender "bristles" at the rear of a tapered, carrot-shaped body. They are 1/2 inch long when fully grown.

Silverfish may be found almost anywhere in the house, but are most commonly found in moist, warm locations (such as around sinks and other plumbing fixtures). They are covered with shiny silver scales that give the body a metallic sheen. They are frequently found in sinks or bathtubs because they fall in seeking moisture and then cannot climb out. Silverfish are most active at night and run very swiftly with a wiggling motion that resembles the swimming action of a fish.

Firebrats are similar to silverfish in overall appearance but lack the silvery sheen. The body color is gray or brown, usually with numerous dark markings that give a mottled appearance. Unlike the silverfish that may be found in any part of a house, firebrats prefer areas of high temperature (90° F and above) and high humidity. Therefore, firebrats are more common in attics and around furnaces, ovens, and water heaters.

Silverfish and firebrats are pests primarily because they are a nuisance and an annoyance. They may consume or stain foods, fabric, paper, books, or wallpaper. Damage to these items is significant, however, only in cases of very large infestations present over long periods of time.

Control of silverfish and firebrats may not be necessary if only a few are present and no damage is noticed or if infestations are limited to small areas. For silverfish, eliminating moisture problems where the pests can develop may be of some benefit. Household residual insecticides applied as sprays, dusts, or baits can be used if conditions warrant. Treat cracks, crevices, wall voids and other likely hiding spots in the areas where the pests are noticed. Sprays need only be applied lightly and in localized areas of infestation. Boric acid dust can be used for firebrats and silverfish. Boric acid has the advantages of being very low in toxicity and very long lasting if applied in dry voids where it will remain undisturbed. However, dusts are more difficult to apply in a light, even coating, especially into cracks and crevices. For more information on insecticides please see "Insecticides for Indoor Use."

Updated 07/14/2005 - 2:31pm