Silverfish and firebrats are nocturnal and hide during the day. If the object they are hiding beneath is moved, they will dart toward another secluded place. They come out at night to seek food and water. Both insects prefer dry food such as cereals, flour, pasta, and pet food; paper with glue or paste; sizing in paper including wallpaper; book bindings; and starch in clothing. Household dust and debris, dead insects, and certain fungi also are important sources of food. However, they can live for several months without nourishment.
Large numbers of these insects can invade new homes from surrounding wild areas, especially as these areas dry out during the summer. They also can come in on lumber, wallboard, and similar products. Freshly laid concrete and green lumber supply humidity, while wallpaper paste provides food.
The common silverfish, is shiny, silver or pearl gray, and about 1/2 inch long, although it can grow as long as 3/4 inch. The common firebrat, is shiny, a mottled gray or brown, and about 1/2 inch long. Adults of both species are slender, wingless, soft-bodied insects with 2 long, slender antennae. Their bodies taper gradually from front to rear to 3 long, thin, tail like appendages.
Although small nymphs (those that are less than 1/8 inch long) lack scales, both large nymphs and adults have them. If you see scales around or beneath damaged items, it is a good indication that these pests are the culprits. The scales are delicate, dust like, and slightly incandescent in the light, and they stick to most surfaces.