The firebrat, Thermobia domestica (Left), silverfish, Lepisma saccharina (Center), and house centipede, Scutigera coleopterata, (Right)
These arthropods are mostly a nuisance rather than economically or medically significant. They may be symptoms of a structural moisture problem that needs attention so should generally not be ignored, particularly if there are large numbers of them.
The firebrat and silverfish are both bristletails (Thysanura) with similar appearance and biologies. The most
common species inhabiting buildings are in the genera Lepisma (silverfish) and Thermobia (firebrat). The
silverfish (Lepisma saccharina) is about 1/2 inch long when fully grown and covered with silvery scales. It is
grayish to greenish in color and its body has a flattened-carrot shape. The firebrat (Thermobia domestica) has a
mottled appearance with patches of white and black, and is shaped like the silverfish. Silverfish and firebrats eat material high in protein, sugar, or starch, including cereals, moist wheat flour, starch in book bindings, sizing in paper, and paper under which there is glue or paste. These insects often attack wallpaper, eating irregular holes through the paper to get at the paste. Silverfish may bite very small holes in various fabrics, including cotton, linen (they can digest cellulose to some extent), and silk. Firebrats will feed extensively on rayon, whereas silverfish usually damage it only slightly.
The house centipede is up to 1 1/2 inches long and has 15 pairs of very long, almost thread-like, slender legs. Each leg is encircled by dark and white bands. The body is brown to grayish-yellow and has three dark stripes on top. Though house centipedes are found both indoors and outdoors it is the occasional one on the bathroom or bedroom wall, or the one accidentally trapped in the bathtub, sink, or lavatory that causes the most concern. However, these locations are not where they normally originate. Centipedes prefer to live in damp portions of basements, closets, bathrooms, unexcavated areas under the house and beneath the bark of firewood stored indoors. They do not come up through the drain pipes.
House centipedes feed on small insects, insect larvae, and on spiders. Thus they are beneficial, though most homeowners take a different point-of-view and consider them a nuisance. Technically, the house centipede could bite, but it is considered harmless to people.
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