Silverfish are the small, teardrop-shaped, silvery insects that dart across bathroom floors and basement walls and wriggle like a fish when you disturb them. They're a classic moisture pest: silverfish live and develop in damp, warm places, which is exactly what New York apartments offer in abundance — humid bathrooms, below-grade basements, laundry rooms and the deep wall voids of pre-war buildings.
They feed on starches and paper: cereals, flour and pet food, the glue and paste in book bindings, wallpaper paste, sizing in paper, and the starch in stored clothing. Because their flat bodies let them slip into narrow crevices, they hide by day inside wall voids, behind baseboards, in closets and bookcases, and around the gaps where pipes pass through walls — then come out at night to feed. That's why a can of spray rarely works: the population you see is a fraction of the one tucked into the moisture-rich voids you can't reach.
Our silverfish programme is part of our general pest treatment: we treat the cracks, crevices and harbourage where silverfish shelter, target the damp areas they depend on, and advise on the moisture and storage conditions sustaining them. Reduce the humidity and seal the gaps, and silverfish lose the conditions they need to survive.
What attracts silverfish, what do they damage, and how do you get rid of them in a NYC home?
The University of California IPM program describes silverfish as shiny, silver to pearl-gray and about half an inch long, with two long antennae and a body tapering to three thin, tail-like appendages; near-identical firebrats are a mottled gray-brown, so finding their dustlike, slightly incandescent shed scales beside damaged items is the surest way to tell which pest you have. (UC Statewide IPM Program — Silverfish and Firebrats)
Silverfish are a moisture problem first: the UC IPM program reports they thrive in damp, warm conditions, favouring relative humidity above 75 percent, and commonly infest basements, laundry rooms and bathrooms — the exact damp pockets of a NYC apartment or brownstone where humidity is rarely controlled. (UC Statewide IPM Program — Silverfish and Firebrats)
Penn State Extension reports that silverfish and firebrats can destroy cereals, books, paper, wallpaper and other starchy items, and UC IPM notes the damage shows as irregularly shaped holes because the insects scrape rather than bite the surface — feeding on paper sizing, book bindings, wallpaper paste and the starch in stored clothing. (Penn State Extension — Bristletails (Silverfish and Firebrats))
Penn State Extension advises that no single method controls silverfish: effective management combines sanitation, de-humidification, habitat modification and only targeted insecticide, cutting off food, water and harbourage at once. UC IPM adds that dehumidifiers and fan ventilation can lower humidity to intolerable levels, with chemical use reserved for large infestations. (Penn State Extension — Bristletails (Silverfish and Firebrats))
Silverfish vs firebrat — how to tell them apart
| Silverfish | Firebrat | |
|---|---|---|
| Colour | Shiny silver to pearl-gray | Mottled gray or brown |
| Size | About 1/2 inch | About 1/2 inch |
| Preferred conditions | Damp and warm, humidity above 75% | Very hot and drier, above 90°F |
| Where found | Basements, laundry rooms, bathrooms | Near ovens, hot-water pipes, furnaces, summer attics |
Signs you have a silverfish control problem
- Small, silvery, teardrop-shaped insects darting across bathroom or basement floors, especially at night
- Tiny holes, notches or surface etching on paper, wallpaper, book spines or stored documents
- Yellowish stains or fine pepper-like droppings in cabinets, drawers and bookshelves
- Damage to starched or stored clothing and natural-fibre fabrics
- Shed skins or a faint dusty residue in damp closets, under sinks and around plumbing
Why Williamsburg sees this
Pre-war buildings and brownstones combine humid bathrooms, below-grade basements and deep wall voids — the damp, crevice-rich conditions silverfish need — so in NYC we treat the moisture and the voids, not just the floor where you spotted one.
Silverfish travel between units through shared plumbing chases and wall voids in multi-unit buildings, so we treat with the building in mind and point you to the underlying moisture source.