Slim, silver-grey, scaly and tapered, silverfish resemble fish, but are garden insects and sometimes household pests. Attracted to moist, dark environments and plentiful food supplies, these 12 mm- (1/2 inch-) long, harmless but annoying creatures live between two and eight years, each female laying over 100 eggs within a lifetime. Silverfish infestations can be a warning sign of damp problems in homes.
Silverfish are attracted to abundant food sources, and can eat many substances commonly found in homes. Most human foods are edible to them -- their favourites are cereals, flour and dried meat. They also eat paper, glue, wallpaper paste and starch, causing damage to books, photographs, wallpaper and other paper products. Silverfish also damage clothing, bedding and towels, as they can eat cotton, linen, rayon and some synthetic fabrics. They've even been known to eat leather and dead insects, and can live without food for many months.
Dark, damp, warm living conditions are attractive to silverfish. They need humidity levels between 75 and 95 per cent to develop, so their presence often indicates a dampness problem. They also prefer temperatures between 21 and 27 degrees Centigrade (70 to 80 degrees Fahrenheit). Silverfish hide during the daytime in permanently dark areas of homes, such as basements, laundry rooms, bathrooms and under floors or piles of clutter, coming out only at night or when disturbed.
Nest sites attractive to silverfish are undisturbed areas of homes where they can reproduce unnoticed. They nest in stacks of books, newspapers or magazines, cardboard boxes and piles of clothing, where they can breed and eat without leaving the safe environment. They also like areas around heating, hot water pipes, behind and in furniture and cupboards. Dampness trapped underneath impermeable flooring, such as laminate or vinyl, in floor and ceiling cracks, or any other nooks and crannies, is very attractive to them.
Controlling silverfish involves making homes less attractive to them and eradicating existing infestations. Resolving any damp problems, such as leaking pipes, trapped water and condensation, is the first step. Piles of books, magazines, newspapers or clothing should be removed. Freezing temperatures kill silverfish, so wrap valued infested items in plastic and place in a freezer for between four and seven days. Allow items to thaw before removing the plastic. Spraying residual insecticides in affected areas kills existing silverfish, but infestations will reoccur as long as suitable living conditions, such as damp, persist.