Silverfish are common household pests (Lepisma saccharinum), recognizable by their silvery, fish-shaped bodies and wriggling movement. These primitive, wingless insects are known for their destructive feeding habits on items high in starch and carbohydrates. While they do not pose a direct threat to human health, their presence often signals an underlying environmental issue within a structure. Understanding their behavior and habitat preferences is the first step in managing these pests.
Understanding Their Nocturnal Habits
Silverfish are strictly nocturnal creatures, confining their activity almost entirely to the hours of darkness. This is a survival mechanism, as they are highly sensitive and adverse to light. They spend the daytime concealed in tight, dark spaces, such as wall voids, under floorboards, or behind baseboards.
Seeing a silverfish during the day often indicates a substantial infestation or that their hiding spot has been disturbed. Their foraging activity, when they emerge to search for food, typically peaks late at night or in the early morning hours. They operate most comfortably within a temperature range of 70 to 81°F (22–27°C).
Ideal Conditions That Attract Silverfish
The presence of silverfish is heavily tied to two environmental factors: high humidity and a suitable food source. They require high humidity to survive, thriving when the relative humidity is consistently between 75% and 95%. These conditions are frequently found in basements, crawl spaces, attics, and bathrooms, particularly where ventilation is poor or moisture accumulates.
Silverfish are drawn to materials rich in carbohydrates and starches, which is the source of their scientific name, saccharinum. Their diet includes common household items like paper, book bindings, wallpaper paste, and certain textiles, as well as cereals, flour, and dead skin cells. They damage these items by scraping the surface to consume the starchy material, often leaving behind irregular holes and yellow stains. The combination of moisture and these starchy materials explains why they are frequently found near plumbing or stored paper goods.
Practical Steps for Control and Prevention
Effective silverfish management relies on modifying the environment to make it less hospitable. The first step involves reducing moisture levels in damp areas, as these insects cannot survive long in low humidity. Installing dehumidifiers in basements and crawl spaces can help maintain indoor humidity levels below 50%, which is unfavorable for silverfish survival and egg hatching. Promptly repairing leaky pipes or dripping faucets is also important, as they provide a constant water source for the pests.
Removing their food sources and access points is the next step in prevention. Paper goods, books, and clothing should be stored in sealed plastic containers instead of cardboard boxes, which are a direct food source.
Regular cleaning and vacuuming eliminate spilled starches and shed insect scales, further limiting their sustenance. Finally, sealing potential entry points with caulk, such as cracks around baseboards, windows, and utility line openings, prevents them from moving easily throughout the structure.