Silverfish and firebrats are common house-invading pests. Considered mostly a nuisance, they also contaminate food with their droppings and scales from their bodies damage paper goods and even stain cloth.
Silverfish and firebrats are usually introduced in the home from some outside source. Considerable time is required for populations to become established, grow and reproduce. Once they are controlled, they generally do not reinfest from outdoors.

Silverfish and firebrats are flattened from top to bottom, elongated and oval in shape. They are easy to recognize by their lack of wings, three caudal or tail projections and two long antennae. Their bodies are covered with fine scales which are silvery to brown in color.

Silverfish develop from egg to young to adult and continue to molt throughout their adult life. They are long-lived, surviving from two to eight years. The silverfish, Lepisma sacchrina, is probably the most important species. The female lays eggs continuously after she reaches adulthood and may lay over 100 eggs during her lifespan. The eggs are deposited singly or in small groups in cracks and crevices and hatch in 3 to 6 weeks. The young are approximately 1/20 of an inch in length. They are white but take on the adult's silver coloring within 4 to 6 weeks. Adults reach a length of about 3/4 of an inch.

Silverfish are extremely sensitive to moisture and require a high relative humidity (75 to 95 percent). They also have a temperature preference between 70 degrees and 80 degrees F.

The firebrat, Thermobia domestica, is quite similar to the silverfish, but is considerably darker. Unlike the silverfish, the firebrat prefers temperatures over 90 degrees F. It also enjoys high relative humidity, somewhere around 70 to 80 percent. Because of their high temperature preference, firebrats are commonly found near heating pipes, fireplaces, ovens and other heat sources.

Silverfish and firebrats are fast running and are most active at night. They generally prefer the lower levels in homes, but are often found in attics as well. They can go for long periods of time, sometimes over a year, without food. They prefer carbohydrates and protein food such as flour, dried meat, rolled oats, paper and even glue. Because they are such general feeders and can survive so long without food, sanitation is of little help in eliminating an infestation. Silverfish are primarily an indoor problem since they are rarely encountered outdoors. They usually are brought into thc home in foodstuffs or other items such as furniture, old books and papers.

Information compiled from John A. Jackman and Phillip J. Hamman
Extension entomologist and Extension urban entomologist
The Texas A&M University System