Silverfish in Missouri Homes: What They Want and How to Eliminate Them

Silverfish are ancient insects — their lineage predates the dinosaurs — that have adapted perfectly to the modern indoor environment. They are secretive, nocturnal, and entirely harmless to people, but they can cause genuine damage to stored materials and are a reliable indicator of conditions in a home that also support mold, dust mites, and other moisture-related problems. Here is what you need to know about managing them.

Identifying Silverfish

Silverfish (Lepisma saccharina) are distinctive and unmistakable once you have seen one:

• Elongated, teardrop-shaped body, flattened, tapering toward the rear
• Shiny, silver-gray scales covering the body — the source of the common name
• Three long tail appendages (cerci) at the rear
• Long antennae at the front
• Body length approximately 12–19mm for adults
• Fast-moving with a distinctive wriggling, fish-like motion — the other source of the name

The firebrat (Thermobia domestica) is a close relative that looks similar but prefers drier, hotter conditions — typically near ovens, water heaters, and heating systems. Silverfish prefer cool and humid conditions.

What They Eat and What Damage They Cause

Silverfish feed on polysaccharides — starches and sugars — which are found in a wide variety of household materials:

• Paper and cardboard — books, magazines, wallpaper, cardboard boxes
• Natural fiber fabrics — cotton, linen, silk (not synthetics)
• Glue and adhesives — including book bindings and wallpaper paste
• Pantry items — flour, oats, cereals, sugar, and dried pasta
• Photographs and stored documents
• Leather

Damage appears as irregular surface feeding — scraped areas, surface notching, and yellow staining from silverfish feces and molted skins. Books and documents stored in humid areas are particularly vulnerable to significant damage over time.

Where They Live in Missouri Homes

Silverfish require high humidity — they prefer environments with 75 to 95% relative humidity and temperatures of 70 to 80°F. In Missouri homes they concentrate in:

• Basements — particularly around stored boxes and along walls where condensation occurs
• Bathrooms — behind toilet bases, under sinks, inside bathroom cabinets
• Kitchens — under sinks, in pantry areas, inside cabinet base areas
• Attics — particularly in humid summer months
• Crawlspaces — the highest humidity areas of many Missouri homes

Control: Reducing Humidity Is the Foundation

Chemical treatment without addressing the moisture conditions that support silverfish produces only temporary results. The most effective long-term control combines moisture reduction with targeted treatment:

• Dehumidify: Run a dehumidifier in the basement, especially during Missouri's humid summer months. Maintain indoor relative humidity below 50% in problem areas.
• Fix leaks: Address any plumbing leaks, roof leaks, or water intrusion that elevates indoor humidity
• Ventilate: Improve crawlspace ventilation and ensure bathroom exhaust fans are used and functioning
• Reduce harborage: Remove cardboard boxes and stored paper materials from high-humidity areas; transfer to sealed plastic bins
• Insecticide dusts: Applied in wall voids, crawlspaces, and under baseboards, desiccant dusts (diatomaceous earth or silica gel) are effective at killing silverfish in harborage areas and remain active long-term in protected dry locations
• Perimeter treatment: Professional perimeter treatment as part of a general pest program addresses silverfish as part of the broader program