Lepisma saccharina

Appearance

Silverfish are nocturnal insects typically 13–30 mm long.
Their abdomens taper 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, despite other members of Thysanura being completely eyeless, such as the family Nicoletiidae.

Like other species in Apterygota, silverfish are completely wingless. They have long antennae, and move in a wiggling motion that resembles the movement of a fish. This, coupled with their appearance, influences their common name. Silverfish typically live for two to eight years.

Naming

The scientific name for the species is ''Lepisma saccharina'', due to its tendency to eat starchy foods high in carbohydrates and protein, such as dextrin. However, the insect's more common name comes from the insect's distinctive metallic appearance and fish-like shape. While the scientific name can be traced back to 1758, the common name has been in use since at least 1855.Other similar insect species are known as silverfish. Two other silverfish are common in North America, ''Ctenolepisma longicaudata'' and ''Ctenolepisma quadriseriata''. ''Ctenolepisma urbana'' is known as the urban silverfish. The Australian species most commonly referred to as silverfish is a different lepismatid, ''Acrotelsella devriesiana''. The firebrat is like a silverfish but smaller and with darker markings of brown and black.

Distribution

Silverfish are a cosmopolitan species, found in Africa, the Americas, Asia, Australia, 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 attics, basements, bathtubs, and showers.

Behavior

The reproduction of silverfish is preceded by a ritual involving three phases, which may last over half an hour. In the first phase, the male and female stand face to face, their trembling antennae touching, then repeatedly back off and return to this position. In the second phase the male runs away and the female chases him. In the third phase the male and female stand side by side and head-to-tail, with the male vibrating his tail against the female. Finally the male lays a spermatophore, a sperm capsule covered in gossamer, which the female takes into her body via her ovipositor to fertilise the eggs.

The female lays groups of fewer than 60 eggs at once, deposited in small crevices. The eggs are oval-shaped, whitish, about 0.8 millimetres long, and take between two weeks and two months to hatch. A silverfish usually lays fewer than 100 eggs in her 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 17 to 66 moults in their lifetime, sometimes 30 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.

Habitat

Silverfish consume matter that contains polysaccharides, such as starches and dextrin in adhesives. These include book bindings, carpet, clothing, coffee, dandruff, glue, hair, some paints, paper, photos, plaster, and sugar. Silverfish can also cause damage to tapestries. Other substances they may eat include cotton, dead insects, linen, silk, or even its own exuvia . During famine, a silverfish may even attack leatherware and synthetic fabrics. Silverfish can live for a year or more without eating.

Silverfish are considered household pests, due to their consumption and destruction of property. However, 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.

Reproduction

The reproduction of silverfish is preceded by a ritual involving three phases, which may last over half an hour. In the first phase, the male and female stand face to face, their trembling antennae touching, then repeatedly back off and return to this position. In the second phase the male runs away and the female chases him. In the third phase the male and female stand side by side and head-to-tail, with the male vibrating his tail against the female. Finally the male lays a spermatophore, a sperm capsule covered in gossamer, which the female takes into her body via her ovipositor to fertilise the eggs.

The female lays groups of fewer than 60 eggs at once, deposited in small crevices. The eggs are oval-shaped, whitish, about 0.8 millimetres long, and take between two weeks and two months to hatch. A silverfish usually lays fewer than 100 eggs in her 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 17 to 66 moults in their lifetime, sometimes 30 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.

Evolution

Together with jumping bristletails, the predecessors of silverfish are considered the earliest, most primitive insects and one of the first animals to colonise dry land. They evolved at the latest in mid-Devonian and possibly as early as late Silurian more than 400 million years ago. Some fossilized arthropod trackways from the Paleozoic Era, known as ''Stiaria intermedia'' and often attributed to jumping bristletails, may have been produced by silverfish.