Silverfish are common in homes, schools and businesses throughout the world. With their penchant for warm, moist, dark habitats, and their love of paper, these insects can be found hiding in wallboard, nibbling at the edges of a favorite book, or eating the wallpaper right off the walls. By identifying the three common types of silverfish, you can take steps to protect your belongings and repel these common pests.
Common North American Silverfish
The common North American silverfish (Lepisma saccharina) is found throughout the continent. It is approximately half an inch long, and a uniform gray-silver color. Like all silverfish it is wingless, but has a jointed, segmented body with parallel sets of legs extending outwards. It's a nocturnal insect, and can be most easily seen near windowsills and shower doors and in other warm, moist, dark places in bathrooms, kitchens and basements.
The four-lined silverfish (Ctenolepisma quadriseriata) takes its name from the four black lines running down its back. The overall color is tan with a gray cast. Like the common silverfish it is half an inch long. It prefers slightly warmer temperatures than the common silverfish, but also requires high humidity and a food source such as the cellulose found in paper.
Gray or Giant Silverfish
The gray or giant silverfish (Ctenolepisma longicaudata) is by far the largest type. Sizes range from three-quarters of an inch to an inch. It has a uniform gray color, sometimes with less of a silvery sheen than the common silverfish. Like the four-line silverfish it prefers hotter temperatures, but also requires humidity and cellulose for food.
The firebrat (Thermobia domestica) is the darkest of the four types of silverfish. Color ranges from moderate to dark mottled gray, with distinctive dark patches on the back. Unlike the other types of silverfish, the firebrat likes to live near furnaces and boilers, enjoying the dark, warm, moist areas near hot water heaters. It is about half an inch long.