Silverfishes
Order:
Thysanura
Family: Lepismatidae
Species: Lepisma saccharina
(L.)
Sometimes referred to as bristletails, silverfish are widely distributed in the United States. The insect depicted above is the common silverfish. Other insects in this family are the firebrat, four-lined silverfish and the gray silverfish.
Silverfish are primitive, wingless insects, without metamorphosis. The young are very much like the adults except for size. As they get older, distinguishing coloration develops. The bodies are slender with a tapering abdomen. The common silverfish is the most slender and delicate of this insect family. This species also has silvery scales covering its body, giving it a silvery appearance.
Biology
Silverfish can live for long periods of time. They also molt continuously throughout their life which may be up to eight years. Silverfish need to mate after each molt so that the female can lay fertile eggs. Females lay eggs in small batches of up to 50 depending on the species, but they generally lay less than 100 eggs during their life span. For this reason, infestations develop slowly. Populations do not build up rapidly. A large infestation in a structure indicates it has been infested for a long time.
Habits
Depending on the species, the habits and habitat for the silverfish or firebrat may vary considerably. In general they are free living and can be found indoors or outdoors. They prefer warm temperatures and moisture (new construction, waterpipes, etc.). The insects are active at night and move quickly.
They feed on a wide variety of foods, usually preferring carbohydrate and protein foods. They have been known to feed on grains, dried beef, flour, starch, paper, and some natural fibers such as cotton. Silverfish have also been reported to go for long periods of time (up to a year) without food, so sanitation alone will not eliminate an infestation.
The species depicted above can live three-and-one-half years and molt 40 times. L. saccharina is sensitive to moisture, preferring 75 to 90 percent humidity. Because of this requirement, it is generally found in the lower levels of buildings and around foundations. It is also common in new buildings where moist conditions may be found.
Control
Each species has different habitats and requirements. In general, temperature and humidity control or lighting in certain areas will reduce populations.
(Courtesy of the National Pest Control Association.)