Silverfish are small, wingless insects with a distinctive, silvery-gray color and a body shape that tapers from head to rear. Their common name is derived from the quick, wiggling motion they use, which mimics the movement of a fish. They are mainly considered nuisance pests because they do not bite or transmit disease to humans, but they cause damage to household items through their destructive feeding habits. Silverfish are nocturnal, meaning they are most active at night, and they tend to hide in dark, undisturbed areas during the day, making them difficult to detect until an infestation is established.
Natural Habitat and Environmental Needs
Silverfish are a cosmopolitan species found worldwide that thrives in environments with high moisture. Their presence in a home often indicates a humidity problem, as they require a relative humidity level between 75% and 95% to survive. Outdoors, these insects are commonly found in dark, moist habitats where they act as decomposers, breaking down dead plant matter. They typically live under leaf litter, beneath rocks, or within decaying wood. When the outdoor environment becomes too dry, silverfish seek out more stable, moist microclimates, which often leads them toward human dwellings. This preference for dampness is the primary driver for their movement indoors.
Common Entry Points into Structures
Silverfish often gain entry into structures by utilizing small openings and unsealed gaps leading from the exterior to the interior. Cracks in the foundation and small crevices in the exterior siding are common pathways, especially at ground level. They can also squeeze through gaps around windows and door frames that have poorly sealed edges or damaged weather stripping. Utility penetrations, such as where pipes and wires enter the home through walls or slabs, also provide easy access points when they are not properly sealed. Silverfish can also be inadvertently transported inside by humans, a method known as passive introduction. They often hitch rides on infested items brought into the home, including cardboard boxes, stored paper items, old books, or materials like firewood. Even small openings like torn window screens or unsealed attic and dryer vents can serve as entry points.
Indoor Attractants and Food Sources
Once inside a structure, silverfish are sustained by persistent moisture and a diet rich in carbohydrates and proteins. Areas with high humidity, such as basements, bathrooms, and kitchens, are particularly attractive, especially near leaky pipes or tubs where condensation occurs. These insects are also drawn to dark, undisturbed locations like wall voids, behind baseboards, and in attics where moisture can accumulate. Their diet consists of matter containing polysaccharides, including starches and dextrin found in various household materials. They frequently feed on the glue used in book bindings, wallpaper paste, and cardboard boxes, causing noticeable damage. Other common food sources include paper products, stored clothing made of natural fibers, flour, cereal, and residual items like dead skin cells and hair.