Silverfish are always wingless and are silvery to brown in colour because their bodies are covered with fine scales. They are generally soft-bodied. Adults are up to three-quarters of an inch long, flattened from top to bottom, elongated and oval in shape, have three long tail projections and two long antennae.
The Firebrat, Thermobia domestica (Packard), is quite similar in habits but is generally darker in colour. The firebrat prefers temperatures over 90°F, but has a similar high humidity requirement. It is common near heating pipes, fire places, ovens and other heat sources.
Females lay eggs continuously after reaching the adult stage and may lay over 100 eggs during her life. Eggs are deposited singly or in small groups in cracks and crevices and hatch in three weeks. Silverfish develop from egg to young to adult within four to six weeks and continue to molt throughout their life. Immature stages appear similar to adults except they are about one-twentieth of an inch long when they first hatch and whitish in color, taking on the adults’ silver colouring as they grow. They are long-lived, surviving from two to eight years. Simple metamorphosis (egg, nymph, adult).
Habitat and Food Sources
Silverfish are chewing insects and general feeders but prefer carbohydrates and protein, including flour, dried meat, rolled oats, paper and even glue. They can survive long periods, sometimes over a year, without food but are sensitive to moisture and require a high humidity (75% to 90%) to survive. They also have a temperature preference between 70 and 80°F. They are fast running and mostly active at night and generally prefer lower levels in homes, but may be found in attics.
Pest Status and Damage
Silverfish are primarily a nuisance pest inside the home or buildings; they can contaminate food, damage paper goods and stain clothing, but are medically harmless. Many of their habits are similar to cockroaches and they appear to be more common as household pests in drier parts of the state. They can occasionally damage book bindings, curtains, and wallpaper.