What Are Silverfish? (Identification, Bites & Damage)

A silverfish is a small (about a quarter to three-quarters of an inch), wingless, teardrop-shaped insect with silvery-grey scales, three long tail bristles, and a darting, fish-like wiggle. It's harmless to people — it doesn't bite or carry disease — but it damages paper, books, wallpaper, and starchy food, and signals excess moisture indoors.

What does a silverfish look like?

Silverfish are easy to recognize once you know the silhouette: a flat, tapered, carrot-shaped body that's wider at the head and narrows toward the tail, covered in fine silver-grey (sometimes pearl or brownish) scales that rub off like powder. They have two long antennae in front and three bristle-like tails at the back, and they move in a quick, side-to-side wriggle that really does look like a fish swimming. Adults reach about half an inch, not counting the tails.

They have no wings and can't fly or jump, but they're fast runners and can climb rough surfaces. You'll usually meet one at night, or when you flip on a bathroom light and catch it darting for a crack.

Silverfish vs. firebrat — quick comparison

Where do silverfish live in your home?

Silverfish chase humidity and darkness. In Fresno homes — even with our dry climate — that means bathrooms, under-sink cabinets, the water-heater closet, laundry rooms, garages, crawl spaces, and the cooler corners of an attic. They also nest inside stored cardboard boxes, stacks of paper, and behind baseboards and loose wallpaper.

If you're finding them stuck in the bathtub or sink, it's usually because they fell in chasing moisture and couldn't climb the smooth sides back out — not because they came up the drain.

What do silverfish eat?

Silverfish are after carbohydrates — the starches and sugars in everyday materials. That includes paper and the glue in book bindings and box seams, wallpaper paste, cereal and flour, pet food, dead insects, and even the sizing in cotton, linen, and silk. They can survive a long time without food, which is part of why infestations build slowly and quietly.

Silverfish eggs and life cycle (and what baby silverfish look like)

Females lay small batches of soft, oval, whitish eggs tucked into cracks and crevices. Nymphs — baby silverfish — look like tiny, pale versions of the adults, whitish at first and darkening to silver as they grow and molt. Silverfish are unusual in that they keep molting throughout their lives and can live for several years, so a population that's been ignored can become well established.

Do silverfish bite? Are they dangerous?

No. Silverfish don't bite people or pets, they aren't venomous, and they don't spread disease. Their mouthparts are built for scraping starch, not skin. The only real harm is to your belongings, and the fact that large numbers point to a moisture problem. Some people can react to silverfish scales as a dust allergen, but the bug itself is not a health threat.

What damage do silverfish cause?

Because they feed on starch and cellulose, silverfish quietly ruin paper goods and fabrics: yellow stains and notched holes in books, documents, and wallpaper; grazed surfaces on cardboard; and small holes in stored clothing and linens. They'll also get into pantry staples like flour and cereal. None of it happens overnight, but an unchecked population can do real damage to keepsakes, photos, and stored clothes over time.

How to tell if you have a silverfish infestation

A single silverfish now and then is normal. Signs of an actual infestation include repeated sightings (especially several at once), yellow stains and feeding holes on paper or fabric, pepper-like droppings in drawers and boxes, and translucent shed skins in bathrooms, closets, or the garage. If you're seeing those regularly, the population has settled in and it's worth treating the source.

When to call a pro

If silverfish keep reappearing after you've cut the humidity and decluttered, the colony is living somewhere you can't easily reach — wall voids, the attic, or deep in storage. At that point a professional crack-and-crevice treatment plus a moisture plan clears them far faster than repeat DIY. Total Pest Control treats silverfish across Fresno and the Central Valley.

📞 Call (559) 472-8200

Silverfish FAQ