The silverfish (Lepisma saccharinum) is a small, wingless, nocturnal insect known for its distinctive metallic, light gray color and fish-like movement. These common household pests have a long, tapered body and three long appendages extending from their abdomen. Because they hide in dark, secluded areas, their exact diet often remains a mystery to homeowners. Understanding what these insects eat is the first step toward effective management.
Addressing the Predation Question
Silverfish are not predators that actively hunt other living insects or bugs in your home. They are classified as detritivores, meaning their role is primarily to consume debris, distinguishing them from hunters like spiders or centipedes. Their diet does not involve live prey, as they lack the necessary anatomy or hunting behavior for capture. They are opportunistic scavengers, however, and will consume dead insects, including the carcasses of other silverfish, for protein. They also eat their own shed exoskeletons (exuviae) to reclaim valuable nutrients.
What Silverfish Actually Consume
The scientific name, Lepisma saccharinum, hints at the silverfish’s primary dietary preference: carbohydrates, particularly starches and sugars. They seek materials containing polysaccharides, which are complex carbohydrates like starch and cellulose. The insect’s midgut produces cellulase, an enzyme that allows it to digest cellulose, a substance most animals cannot break down.
This unique ability causes them to target paper, cardboard, and textiles made of natural fibers such as cotton, linen, or rayon. Their diet includes the starchy sizing in fabrics, the glue in book bindings and wallpaper paste, and pantry staples like flour and cereal. They also consume less conventional items, such as dandruff, hair, and certain types of mold.
Why Silverfish Are Considered Pests
Silverfish are considered pests because their preferred diet significantly overlaps with valuable human property. Their consumption of paper and adhesives leads to the destruction of documents, photographs, and books, often leaving irregular feeding marks and holes. They also damage wallpaper by eating the paste behind it, causing the paper to peel away.
When they infiltrate pantries, they chew through packaging to access starchy contents like flour and cereal. This feeding contaminates stored food with their waste and shed scales, rendering the products inedible. They also damage clothing, especially silk and linen, leaving small holes and yellow stains on the material.
Environmental Factors and Prevention
Silverfish thrive in environments with high humidity, which is the most important factor attracting them to a home. They prefer relative humidity levels between 75 and 95 percent and temperatures ranging from 70 to 90 degrees Fahrenheit. These conditions are typically found in basements, attics, kitchens, and bathrooms, especially in areas with poor ventilation or water leaks.
Prevention Strategies
Preventing an infestation centers on controlling moisture and denying access to their food sources. Installing a dehumidifier in damp areas like basements and crawl spaces can lower the relative humidity below the threshold they need to survive and reproduce. Promptly repairing leaky plumbing or dripping faucets eliminates the dampness these insects rely on. Resource denial is accomplished by storing all dry goods, including flour and cereals, in thick, airtight plastic or glass containers. Important documents, photographs, and valued fabrics should also be kept in sealed storage boxes. Sealing cracks and crevices in walls, flooring, and baseboards eliminates the dark, undisturbed hiding spots where they live and breed.