Silverfish are nocturnal, elongated and flattened insects typically 0.51–0.98 inches long. Their abdomen tapers at the end, giving them a fish-like appearance. The newly hatched are whitish, but develop a greyish hue and metallic shine as they get older. They have three long cerci at the tips of their abdomens, one off the end of their body, one facing left, and one facing right. They also have two small compound eyes.
Silverfish completely lack wings. They have long antennae, and move in a wiggling motion that resembles the movement of a fish. This, coupled with their silver-scales and fish-like appearance, influences their common name. Silverfish typically live for two to eight years.
Silverfish are a species, found in Africa, North America, Europe, Australia, Asia and other parts of the Pacific. They inhabit moist areas, requiring a relative humidity between 75% and 95%. In urban areas, they can be found in basements, bathrooms, garages, closets, and attics.
The female lays groups of less than sixty eggs at once, deposited in small crevices. The eggs are oval-shaped, whitish, about 0.8 millimetres (0.031 in) long, and take between two weeks and two months to hatch. Silverfish usually lay fewer than one hundred eggs in their lifetime.
When the nymphs hatch, they are whitish in colour, and look like smaller adults. As they moult, young silverfish develop a greyish appearance and a metallic shine, eventually becoming adults after three months to three years. They may go through seventeen to sixty-six moults in their lifetime, sometimes thirty in a single year, which is much more than usual for an insect. Silverfish are among the few types of insect that continue to moult after reaching adulthood.
The lifespan of a silverfish varies from two to eight years.
Silverfish consume matter that contains starches and adhesives. These include glue, book bindings, plaster, some paints, paper, photos, sugar, coffee, hair, carpet, clothing and dandruff. Other substances that may be eaten include cotton, linen, silk, synthetic fibres and dead insects or even its own moulted exoskeleton. During famine, a silverfish may even attack leatherware and synthetic fabrics. Silverfish can live for a year or more without eating.
Silverfish are considered a household pest, due to their consumption and destruction of property. Although they are responsible for the contamination of food and other types of damage, they do not transmit disease.
Earwigs, house centipedes and spiders are known to be predators of silverfish.