Bristletails are often referred to as a type of silverfish, but bristletails actually make up members of the Microcoryphia order of insects. There are 24 species of bristletails in the United States and 300 to 400 species in the world.
They are wingless with a cylindrical body. While many types of silverfish seek indoor environments, there are bristletails species found in grassy or wooded habitats, usually under bark, decaying leaves, in rocks or under stones.
The common silverfish, with the common name Leisma saccharina, is wingless and grows to about 1/2 inch in length. It seeks indoor environments that are damp---bathrooms, kitchens and basements. They are active at night and hide during the day, avoiding light. The common silverfish can live up to eight years.
The four-line silverfish, with the scientific name Ctenolepisma quadriseriata, has four dark lines down its stomach and is a bit longer than the common silverfish. The four-lined silverfish tends to live in flowerbed mulch and under roof shingles. If it moves indoors, it will often be found in attics.
The gray silverfish, with the scientific name Ctenolepisma longicaudata, is completely gray and often dark in color. It tends to live in crawl spaces, attics and pipes in bathrooms.
The firebrat, scientific name Thermobia domestica, is oblong with a yellowish body. It seeks out living conditions where the temperature is 90 degrees or hotter, such as around furnaces and fireplaces. It can also often be found in insulation that surrounds heating pipes. These insect feeds mostly at night and seeks out book bindings and paper products.
Jumping Bristletail, with the scientific name Pedetontus sp., grows to size of more than 1/2 inch in length and is silver or gray in color. These tend to live under rubble, stones, decaying leaves and bark.