Silverfish, while not harmful to people or their pets, can create havoc in pantries and on bookshelves. They hide in crevices between surfaces by day, and by night they scuttle to nearby food sources to dine. Attracted by carbohydrates (starches) and protein, silverfish are most famous for munching on book paper and glue, wallpaper, and carpets. However, these pests also munch on clothing. The silverfish’s close relative, the firebrat, has similar habits.
Like most insects, silverfish and firebrats undergo several life stages; to control these insects effectively, understanding their life cycle helps.
- Adults: Silverfish are wingless oval-shaped insects up to 2/5 to 3/4 inch long with three extended tail projections and two elongated antennae. Fine silver- to brown-colored scales cover their bodies. Silverfish and their near relatives prefer temperatures ranging from 70 to 80°F and high humidity (between 75 and 90%); however, they can adapt to other conditions. The firebrat is darker colored and prefers temperatures over 90°F but has a similar high humidity requirement. Both silverfish and firebrats molt continuously throughout their two- to three-year life span, leaving behind their smaller hard skeletons each of the 50 to 60 times they molt.
- Eggs: Each female can lay 100 eggs during her lifetime, usually depositing them in gaps between surfaces. Nymphs typically hatch about 40 days later.
- Nymphs: The immature stages look like small adults, at 1/20 of an inch. The immature silverfish molts seven to ten days after hatching; each growth stage between molts takes about two to three weeks. Nymphs undergo six to seven molts before reaching adult size.
To prevent infestations of silverfish and firebrats, make susceptible areas uninviting. Seal cracks and crevices with putty or caulking. Repair leaks promptly to eliminate water sources. Keep humidity low in storage areas by using air conditioners or dehumidifiers. In addition, store foods, books, magazines, newspapers, and fabrics in sealed plastic containers. Vacuum closets regularly to remove silverfish, as well as around heat pipes, fireplaces or woodstoves, ovens, and other heat sources where firebrats prefer to live. Remove and inspect items from off-site storage boxes before bringing them inside.
Signs of a silverfish infestation include damaged paper edges that appear asymmetrical or notched. Irregular holes eaten through paper or small irregular scrapings on book bindings characterize heavier infestations. Textiles attacked by silverfish may show yellow stains, scales, and dark feces.
Once silverfish settle in, several methods can help eliminate them. Apply a flea spray for the house or other indoor flea control measures in tight cracks and crevices and around baseboards. To kill silverfish or firebrats on infested items, bag and place them in the freezer for several days.
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