You may have never heard of silverfish before, but after you see one, it may be hard to forget. Silverfish are the epitome of creepy bugs with their distinctive appearance and alarming movements. While silverfish are not dangerous, you definitely do not want them in your home. If you have questions about silverfish, we have the answers. Learn how to identify, prevent, and control these household pests.
What do silverfish look like?
Silverfish (lepisma saccharina) are known for their fish-like looks and movements, but they are definitely not fish. Silverfish are small, wingless insects that are tear-drop shaped. As the name suggests, these insects are normally bluish-silver in color but can also be white or brownish-grey. Silverfish average 13-19 mm in length. They have 6 legs and 2 long antennae. Their elongated body tapers to a narrow rear end where 3 long bristles (cerci) protrude. If the physical description isn’t enough for you to confirm their identity, their movements may seal the deal. Silverfish move in a wiggling motion that makes them appear to be swimming. Despite this strange movement, silverfish are fast and agile runners.
Christian Fischer [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)], from Wikimedia Commons
Silverfish are also sometimes referred to as “bristletails” because of the appendages that protrude from the end of their abdomen. The term bristletail can also apply to firebrats (thermobia domestica). Firebrats are very similar to silverfish with a few key differences. The Penn State Entomology Department describes these differences. Firebrats have tufts of brown scales giving them a slightly mottled appearance and color. Firebrats also prefer very warm environments near furnaces, hot water pipes, and attics. Despite these differences, control measures for firebrats and silverfish are essentially the same.
Firebrat– an insect very similar to a silverfish
Silverfish Life Cycle
Silverfish undergo gradual metamorphosis, meaning that the immature stages look very similar to adults, but they lack the ability to reproduce. A female silverfish will typically lay about 100 eggs in her lifetime. These eggs are very small, white, and oval-shaped, and are typically laid in small cracks or crevices or under stones or leaf litter.
After the eggs hatch, the young silverfish are called nymphs. They are small and white, but look and behave very similar to adults. They will soon start to shed their skin, or molt, as they develop. During their lifetime (generally 2-3 years) they may molt 17-66 times. This is significantly more than most insects. These cast off skins can contribute to allergies because they can get into the air and be breathed in. 
Where do silverfish live?
Silverfish are found throughout the world in Africa, the Americas, Australia, Eurasia, and the Pacific. They live in dark, warm, humid environments. They prefer a relative humidity of 70%-90% and a temperature from 70-85 degrees. When they enter homes, they seek out environments that meet these criteria like attics, kitchens, bathtubs or showers, and under sinks. 2
Are silverfish dangerous? Do silverfish bite?
Silverfish do not bite, sting, or transmit disease. Their appearance can be unnerving to unexpecting homeowners, but they are not known as a dangerous insect. They can cause other problems though. Silverfish infestations attract insects that want to eat them like carpet beetles, earwigs, centipedes, and spiders. They can also cause allergies in some susceptible individuals due to their constant molting. The biggest concern with silverfish is the damage they can do to personal items within a home.
What do silverfish eat?
Silverfish eat a variety of substances. As the scientific name saccharina implies, silverfish eat polysaccharides like sugars, starches, and dextrin. This can include things like: book bindings, photos, glue and other adhesives, wallpaper, clothing, sugar, cotton, paint, hair, linens, and pantry foods. They also are attracted to foods high in protein like dried beef and dead insects. A major silverfish infestation can wreak havoc on photo albums and book collections. Silverfish can go for almost a year without eating as long as water is plentiful.
Silverfish Damage By Micha L. Rieser from Wikimedia Commons
What are some signs of a silverfish infestation?
Silverfish are nocturnal creatures, meaning they are mostly active at night. They hide in damp, warm areas. These factors make it difficult to catch a silverfish infestation early. Oftentimes, they may go unnoticed for quite some time until the population has exploded. If you want to prevent a large infestation, knowing the signs and acting on them quickly is key. Be on the lookout for these things.
- Live Silverfish. A single silverfish does not mean that you have an infestation, but it should be a warning to be on the lookout for other signs. The most common places to find silverfish are in sinks and bathtubs. Although silverfish are fast runners, they cannot climb vertical surfaces well and will often get stuck.
- Feces. Silverfish fecal matter is fairly unique, so it can be used for identification purposes. It looks like small, black, spherical peppercorns. If you know what you are looking for, this can be helpful, but to the untrained eye, it may just blend in with the dirt and dust in your home.
- Yellow Stains. Wherever silverfish are active, you will most likely find yellow stains. These small stains are most obvious on papers and fabrics.
- Shed Skins. Since silverfish molt frequently, these skins can accumulate over time, though they are often hard to see.
- Silverfish damage. When silverfish feed on things, they will leave irregular shaped holes and notches on books, fabrics, wallpaper, etc.
How do I prevent silverfish?
There are many things that can be done to prevent silverfish problems in your home. Prevention falls into 4 main categories: moisture control, proper storage, sanitation, and exclusion efforts. 3
Get rid of excess moisture
- Use a dehumidifier
- Repair leaky faucets and drains
- Repair wood that has suffered water damage
- Eliminate standing water around your yard and home
- Install fans in shower areas
- Clean gutters and downspouts
- Ensure proper drainage
- Run the air conditioner
- Open vents in attics and crawl spaces to reduce humidity
Store Items Properly
- Keep food items sealed in metal, glass, or heavy plastic containers
- Store old books, magazines, photos etc. in sealed plastic containers rather than cardboard boxes. If silverfish are common in your area, don’t store these things in attics, basements, or garages where they may be damaged without being noticed.
- Inspect boxes and containers before bringing them into your home
- Keep your home clean
- Wash dishes immediately after use
- Keep the pantry clean
- Vacuum and sweep floors regularly
- Use the crevice tool to clean cracks and crevices
- Reduce clutter
- Keep the yard clean of debris, leaf litter, wood piles, and grass clippings
- Ensure that windows and doors have screens that are free of rips or tears
- Apply weatherstripping to windows and doors
- Use caulk to seal small cracks. Expandable spray foam and steel wool can be used for larger holes and gaps (especially around plumbing)
- Use fine wire mesh to cover vents
How do I get rid of silverfish?
Silverfish are attracted to sugar and starches, so baits and lures utilizing these things can be beneficial. Harris Famous Roach Tablets provide great control of silverfish, roaches, and waterbugs. Just place these tablets in out of the way places, and the silverfish will find them.
Basic sticky traps can be used to monitor silverfish populations and help you catch problems fast. Traps should be used as part of a comprehensive control plan. Place traps in areas of the home that are dark and damp like bathroom cupboards, laundry rooms, basements, etc.
Dusts are another method of silverfish control. Dusts are excellent in areas that are difficult to reach like wall voids, behind baseboards, under siding, and in attics. Dusts can last up to 6 months if it is out of the elements. Harris makes a boric acid powder for silverfish control. The attached straw allows you to reach into cracks and crevices were insects hide.
Fast acting aerosols using pyrethrins will kill silverfish on contact. This method of control should be used with others because it will not control the silverfish over a long period of time. Aerosols work well when the silverfish are in areas that you can easily reach, and you want the job done quickly.
Residual pesticides are a great way to keep silverfish and many other pests out of your house. They generally last several months. Always follow label directions when using chemicals. Most residuals suggest spraying up from the foundation 2-3 feet and out from the house 2-3 feet. This creates a barrier around the perimeter of your home.
For home pest control products that you can trust, Harris is the answer. Harris is America’s oldest EPA registered brand and has been helping homeowners get rid of pests since 1922. Take back your home, and join the Harris family today!