Invertebrates

Silverfish

Lepisma saccharinum · also called silverfish, fishmoth

Not Evaluated omnivoreherbivore Temperate forest Temperate grassland

A silverfish is the little metallic insect that darts out from behind the books or wriggles helplessly in the bath. Its teardrop body and quick side-to-side movement look like a fish swimming across the floor. It belongs to one of the oldest insect lineages on Earth, it eats the starch in your paper and wallpaper paste, and it can live for the better part of a decade.

Overview

Silverfish are wingless insects of the order Zygentoma, whose body plan appeared over 400 million years ago, before insects had wings. The carrot-shaped body is covered in fine silvery scales and ends in three long tail bristles, with two long antennae up front. They eat carbohydrates — the starch in paper, cardboard, book glue, wallpaper paste, flour, and photographs — and can even digest cellulose.

An unusually long, odd life

A silverfish never stops moulting — dozens of times across a life of 6 to 8 years, long for so small an insect. It also mates without touching: the male spins a silk thread, leaves a sperm packet under it, and the female collects it after an antenna-touching courtship dance.

In the house

Silverfish need humidity and darkness, so they gather in bathrooms, kitchens, basements, and behind bookshelves, coming out at night. They do not bite, sting, or spread disease, but a large population damages books, documents, textiles, and stored food. Drying out the air is the most effective control.

Status

Not evaluated and in no danger — one of the most successful insects of the built environment, with many free-living relatives under bark, in leaf litter, in caves, and in ant nests.

Silverfish: common questions

Are silverfish harmful or dangerous?

Not to people. Silverfish do not bite or sting, they carry no disease, and they do not damage the fabric of a house, wood, wiring, or plaster. What they do damage is paper-based and starchy material, in that they eat books and their bindings, documents, photographs, wallpaper, cardboard boxes, and stored flour, cereal, and dried goods, along with cotton and linen textiles. A few silverfish are a minor nuisance, but a large, established population in a bookcase, archive, or pantry can cause real losses over time, and the shed scales may bother people with sensitive airways.

Why do I have silverfish in my bathroom?

Because it is humid, dark, and quiet, which is exactly what silverfish need. They cannot tolerate dry air for long and they avoid light, so they gather in the dampest rooms, bathrooms, kitchens, basements, and laundry areas, hiding in wall voids, under skirting, and behind fittings by day and coming out at night. Finding them stranded in a sink or bath is common, because they wander in looking for moisture and cannot climb back out of the smooth basin. Reducing humidity with ventilation or a dehumidifier is the most effective long-term control.

How long do silverfish live?

Surprisingly long for such a small insect. A silverfish can live around three years commonly and up to six to eight years in good conditions, and it stays active and keeps breeding for most of that time. It also breaks the usual insect rule of stopping development at adulthood, in that a silverfish keeps moulting its skin throughout its life, sometimes fifty or more times. Slow development, a long life, and steady egg-laying mean that once silverfish are established in a suitable building they are persistent and build up gradually rather than in sudden bursts.

What is the difference between a silverfish and a firebrat?

They are close relatives in the same order and look similar, both small, wingless, tapered, and three-tailed. The key difference is temperature preference. A silverfish likes cool to moderate, very humid places and is the one usually found in bathrooms and basements. A firebrat prefers hot, humid spots and turns up around ovens, boilers, hot water pipes, and heating ducts, and it is mottled brownish rather than silvery grey. Both feed on starches and both are harmless to people, and the same control measures work on each.

Sources & further reading

Written by HideShark Editorial Team · reviewed by HideShark Science Desk. Published September 11, 2026. Last updated September 11, 2026.

Quick facts

Scientific name: Lepisma saccharinum
Diet: A feeder on carbohydrates, especially starches and sugars, including the starch in paper, cardboard, book bindings, wallpaper paste, photographs, cotton and linen, dried food, flour, and rolled oats, and the glue in bookbindings and box seams, and it can also digest cellulose with the help of gut microbes
A living antique: Silverfish belong to the order Zygentoma, a lineage of wingless insects whose basic body plan appeared before insects evolved wings, more than 400 million years ago, so a silverfish scuttling across a bathroom floor is close in form to some of the first insects on land
Built like its name: The body is carrot or teardrop-shaped, tapering from a broad front to a narrow rear, covered in fine silvery scales that rub off easily, and it ends in three long bristle-like tails, while two long antennae sweep the front, and the animal moves in quick darting, side-to-side wriggles that look like a fish swimming
It never stops moulting: Unlike most insects, which stop moulting once they become adult, a silverfish keeps shedding its skin throughout its life, dozens of times, and it can keep growing, mating, and laying eggs across a lifespan that may reach 6 to 8 years, very long for so small an insect
A courtship dance: Silverfish mate through an elaborate ritual in which the male and female touch antennae, the male runs away and returns, and eventually the male spins a fine silk thread and leaves a sperm packet under it for the female to pick up, so the two never actually make direct contact to mate
Loves damp and dark: Silverfish need high humidity and avoid light, so in homes they concentrate in bathrooms, kitchens, basements, laundry rooms, wall voids, and the backs of cupboards and bookshelves, emerging at night, and they become scarce where the air is kept dry and well ventilated
Mostly harmless: Silverfish do not bite, sting, or spread disease, and they do not damage the structure of a building, but a large population can spoil books, documents, artwork, wallpaper, and stored textiles and food, and their scales and droppings can be a minor allergen
Range: Worldwide inside heated buildings, concentrated in humid, dark, undisturbed places such as bathrooms, kitchens, basements, cupboards, wall cavities, and among stored books and papers, and in warm climates also living outdoors under bark, stones, and leaf litter, with the wider order found in nearly every land habitat including deserts, caves, and social-insect nests.
Conservation status: Not Evaluated ≈ The common silverfish is not assessed for conservation and is in no danger. It is one of the most successful insects of the human-built environment, found in buildings across the world, and it descends from and still has many free-living relatives that live under bark and stones, in leaf litter and caves, in the nests of ants and termites, and in deserts, several of which are specialised and localised. Numbers of the household silverfish in a given building rise and fall with humidity and are reduced, not by any threat to the species, but deliberately by drying out the air, sealing entry points, and removing food sources such as loose paper and old cardboard in the wild