What causes silverfish in a NYC apartment?

Moisture plus starch. Silverfish live and develop in damp, warm places and feed on paper, glue, wallpaper paste, cereals and starched fabric, so humid bathrooms, basements and laundry rooms — combined with stored paper and food — are what draw them in. Pre-war NYC buildings, with their damp basements and deep wall voids, offer exactly those conditions.

Are silverfish dangerous or do they bite?

No. Silverfish don't bite people and don't spread disease. The harm they do is to belongings — they scrape and notch paper, books, wallpaper, documents and starched clothing with their weak jaws. They're a nuisance and a property-damage pest, not a health risk.

Why do I keep finding silverfish in my bathroom?

The bathroom is usually the dampest room in a NYC apartment, and silverfish concentrate wherever it's humid and there are crevices to hide in around plumbing. Improving ventilation, fixing leaks and running a fan or dehumidifier to drop the humidity makes the bathroom far less hospitable to them.

Will silverfish go away on their own?

Rarely, because the conditions that drew them — dampness and accessible starch — usually stay put. Silverfish are also long-lived (they can survive two to three years and produce dozens of offspring), so an untreated population tends to persist. Removing the moisture and food and treating their harbourage is what clears them.

When should I call a professional for silverfish?

If silverfish keep reappearing after you've reduced moisture, if they're damaging books or stored items, or if they're turning up across a multi-unit building, the source is usually in damp wall voids beyond your reach. A professional treats the crack-and-crevice harbourage and helps you target the underlying moisture.

How to Get Rid of Silverfish in Your NYC Apartment

The short answer

Silverfish are a moisture pest, so getting rid of them means drying out where they live and cutting the starchy food they eat — then treating the crevices they hide in. Silverfish live and develop in damp, warm places such as bathrooms, basements and laundry rooms, and feed on paper, glue, wallpaper paste, cereals and starched fabric (UC IPM). Lower the humidity, seal away their food, and seal and treat the cracks around baseboards and plumbing where they shelter.

What silverfish are and why NYC apartments suit them

Silverfish are small, silvery, teardrop-shaped insects that wriggle like a fish when disturbed. They are nocturnal and hide during the day, coming out at night to seek food and water (UC IPM). Their flat bodies let them slip into narrow crevices, and they shelter in cracks around doors and window casings, behind baseboards, in closets and bookcases, and in the gaps where pipes pass through walls (UC IPM).

That’s a near-perfect description of a New York apartment. Pre-war buildings and brownstones combine humid bathrooms, below-grade basements and laundry rooms with deep baseboard gaps and wall voids — the damp, crevice-rich conditions silverfish need. And because they’re long-lived — silverfish can live for at least two to three years and produce more than 50 offspring (Penn State Extension) — an untreated population settles in rather than passing through.

Step by step

Cut the moisture — ventilate bathrooms, fix leaks, run a dehumidifier in damp basements and laundry rooms.
Remove their starchy food — seal cereals, flour and pet food; keep paper, books and starched fabric out of humid spots.
Seal and treat the crevices — baseboards, window and door trim, gaps around plumbing.
Address the wall voids — the visible silverfish are a fraction of the damp-void population.

Why DIY sprays usually fail

A can of spray kills the silverfish you can see, but it does nothing about the population hidden in damp wall voids and the conditions sustaining them. Silverfish destroy cereals, books, papers, wallpaper and other starchy items, scraping the surface with weak jaws (Penn State Extension), and they’ll keep doing it as long as the dampness and food remain. Lowering humidity and removing their food does more lasting good than any spray — and in a humid pre-war building, that moisture source is often shared and hard to reach.

When to call a professional

If silverfish keep coming back after you’ve reduced moisture, if they’re damaging books or stored documents, or if they’re appearing across a multi-unit building, the harbourage is usually in damp wall voids beyond your reach. Our silverfish control service treats the crack-and-crevice harbourage where silverfish shelter and helps you target the underlying moisture — so they lose the conditions they need to survive.