Southern Utah pest library
Silverfish Identification
Silverfish are small, wingless, silvery-gray insects with a fish-like wiggle and three long tail filaments. They love damp, dark spaces, basements, bathrooms, under sinks, and inside cardboard boxes, where they feed on paper, glue, starches, and stored fabrics. They’re harmless to people but can quietly damage books, photos, and stored keepsakes over time.
The common silverfish (Lepisma saccharina) is about a half-inch to three-quarters of an inch long as an adult, with a tapered, carrot-shaped body covered in fine, metallic silver scales. Three long bristle-like appendages extend from the rear, with two longer antennae sweeping from the head, giving them an unmistakable look. They run with a quick, side-to-side wiggle that resembles a tiny fish on land. People sometimes confuse them with firebrats, which prefer hot environments like attics and look slightly more mottled brown. Both belong to a primitive order of insects that have been around essentially unchanged for millions of years. Silverfish are wingless, can’t jump, and rely on speed and tight crevices to escape.
Quick ID
What Are Silverfish? Quick ID
One of the oldest insects on earth: wingless, scaly and living on starch and moisture. In Southern Utah they stay in the humid rooms.
Size
1/2 to 3/4 inch
A flat, carrot-shaped body that tapers to the tail.
Color
Silvery gray
Metallic scales, long antennae and three long tail bristles.
Where in Southern Utah
Bathrooms and boxes
Bathrooms, laundry rooms, sink cabinets and cardboard storage. Firebrats like hot spots near water heaters.
Danger level
Property damage
No bites or disease, but they graze on books, photos and stored fabric.
Low Risk
Seeing Silverfish? We can help.
A licensed technician will inspect, treat the problem areas, and come back free if they return between visits.
Where Silverfish Live in Utah
Silverfish thrive wherever it’s humid and dark. In Utah, drier outdoor air keeps overall populations smaller, but they still settle in microclimates that hold moisture, bathrooms, basements, laundry rooms, kitchen sink cabinets, and crawl spaces. They’re most often found in undisturbed storage areas: cardboard boxes of old books, photo albums, paper records, holiday decorations, and stored linens. Roof leaks, plumbing condensation, and poorly ventilated bathrooms create exactly the pockets they need. Outdoors, they may shelter under mulch, stones, or wood debris, but they tend to stay close to structures.
Why They Get Into Homes
Silverfish are drawn in by humidity and held there by food. They feed on starches and polysaccharides, which is a fancy way of saying they eat paper, book bindings, wallpaper paste, cardboard, dried pasta, cereal residue, photographs, and even some natural fibers like cotton and silk. Glue on book spines and the backs of postage stamps is a known favorite. They prefer to feed undisturbed, so storage areas that don’t get touched for months are ideal. Many infestations actually arrive when silverfish hitchhike in on cardboard boxes or stored paper goods from a previous home, garage, or storage unit, then settle in wherever the humidity stays high enough.
Signs You Have a Silverfish Problem
Because silverfish are nocturnal and quick to hide, the evidence is often easier to find than the bugs:
- Live silverfish darting away when you move a stored box or turn on a bathroom light
- Tiny pepper-like droppings on shelves, in drawers, or inside boxes
- Yellowish stains, holes, or notched edges on paper, photos, or wallpaper
- Damaged book bindings, especially around the glued spine
- Shed skins, pale, papery, and translucent, in storage areas
- Chewed cardboard boxes and frayed natural-fiber fabrics
- Activity concentrated in humid rooms like bathrooms, laundry rooms, and basements
What’s the Damage?
Silverfish don’t bite, sting, or transmit disease, and they aren’t a meaningful health threat. The real cost is to stored belongings. A long-running silverfish population can quietly damage old books, family photos, important documents, vintage wallpaper, and stored fabrics, items that often can’t be replaced. They can also contaminate dry pantry goods like flour, oats, and cereal if those are stored in flimsy packaging. Most damage builds up slowly over months or years, which is why people often don’t notice the problem until they pull out a long-stored box and find chewed pages or a thriving population inside.
Found them in old boxes?
Move papers and photos into sealed plastic bins today, then vacuum the shelf and check nearby rooms for moisture.
DIY or a pro
Silverfish Control: How to Get Rid of Silverfish
Take away the moisture and the food at the same time, then treat where they hide.
What you can do yourself
- Run the bathroom fan for 20 minutes after every shower.
- Fix slow drips under sinks and around the water heater.
- Store paper, photos and books in sealed bins, not cardboard.
- Set sticky traps along baseboards to see where they travel.
- Caulk baseboard gaps and pipe openings where they hide by day.
When to Call a Professional Silverfish Exterminator
Light silverfish activity often responds well to dehumidifying and decluttering, but persistent populations, especially in finished basements, multi-room sightings, or homes with chronic moisture issues, usually need help. A professional treatment targets harborage areas with appropriate products and helps identify the moisture conditions feeding the problem. Learn more about our pest control services. Request a free quote.
Our residential pest control treats baseboards, plumbing gaps and storage areas where they hide, and the same visits cover the crickets, earwigs and spiders that share those spaces.
How to Prevent Silverfish Around Your Home
Silverfish prevention is mostly about removing the humidity they depend on:
- Run a dehumidifier in basements, crawl spaces, and chronically damp rooms
- Use bathroom exhaust fans during and after showers
- Repair roof leaks, plumbing drips, and condensation issues quickly
- Store books, photos, and important papers in sealed plastic bins instead of cardboard
- Keep pantry staples like flour, cereal, and pet food in airtight containers
- Seal cracks along baseboards, around pipes, and behind cabinets
- Vacuum and rotate stored items periodically so harborage doesn’t sit undisturbed
- Improve ventilation in attics and crawl spaces to keep humidity down
Protect the Things You Can’t Replace
We find the moisture feeding the problem and treat the hiding spots. If pests come back between visits, so do we, free.
Questions
Common Questions
Do they bite?
No. They don’t bite, sting or carry disease. The cost is to paper, photos and fabric.
Why do I have them in a desert home?
The outdoor air is dry, but bathrooms, laundry rooms and sink cabinets hold enough moisture for them.
How are firebrats different?
Firebrats are close cousins that handle heat better, so they turn up near water heaters, furnaces and hot garages.
When should I call a silverfish exterminator?
When you see them in several rooms, or they keep coming back after you have dried out the humid spots.
Need them gone? See how our bi-monthly pest control works. If pests come back between visits, so do we, free. Live in Washington County? Learn about St. George pest control services.
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