You may have seen the signs: Your books have chewed bindings and pages, you have found the pepper like substance in your cabinets and pantry, or maybe you have actually found one in your flour. Silverfish are tiny insects, but infestations can be very destructive to your home and possessions. While they don’t destroy a home the way termites do or bring with them the health problems of cockroaches, they do present their own set of issues for homeowners. The best way to get rid of silverfish is to understand them and their behaviors. This guide will help you to learn how to get rid of silverfish effectively.
What are Silverfish?
Though not as prevalent as other household pests, silverfish are still a nuisance. They are part of the order Thysanura which falls under the subclass Apterygota [1]. This means that they certain distinct characteristics, particularly physical. For instance, they rarely go through a metamorphosis and are wingless. The name Thysanura comes from the Greek word “thysano-“ which means “fringed”, and “ura” which means “tail.” This meaning refers to the fringe tail of the silverfish, the three long filaments that extend beyond the tail of the insects’ body to form a fringe [2]
The adult silverfish is from a half inch long to just under an inch. The body is elongated and tapers down through the abdomen to the tail so that it resembles a tear drop. It has six legs with long, multi-segmented antennae, and a single medial filament and two lateral cerci. The three are usually equal in length. The body is flattened and covered in silvery scales. They can run fairly fast, but they are wingless so they can’t fly and they are not able to jump [3].
There are more than 370 species of silverfish worldwide, but only about 18 species are in North America. They are nocturnal, hiding in underbrush, under leaves, or under stones during the day. At night they leave their hiding places to search for food. Some species can handle the dryer environment of domestic environments, choosing the warmer, darker, more moist and humid areas like basements and even attics although they can be found in the kitchen and bathroom. They are scavengers, feeding on starchy vegetable matter, lichens, or algae. This means that books, wallpaper, even your dry goods in your kitchen are all fair game.
Types of Silverfish
Of the 18 types of silverfish in the United States, there are four main types that should concern homeowners. By learning a little bit about the different types you can take preventative measures to keep them out of your home, thus protecting your belongings.
The four types silverfish in the U.S. are the Common North American Silverfish, the Four Lined Silverfish, the Gray or Giant Silverfish, and the Firebrat [4].
- Common North American Silverfish – The Lepisma saccharina, or common North American silverfish can be found in every state on the continent. Adults are around a half an inch long and the color is a uniform silvery gray. It does not have wings, making it unable to fly. The body is flattened, segmented and jointed with six legs, three on each side.
The Common North American Silverfish moves very quickly but in not able to jump. It is nocturnal, preferring harborage in human dwellings, seeking out the dark, moist, warm areas like basements, laundry rooms, kitchens, and bathrooms. It can also be found on or near shower doors, shower curtains, and windowsills but is very rarely found outside [5].
- Four Lined Silverfish – The Ctenolepisma quadriseriata, or four lined silverfish, gets its name from the four vertical lines that run up and down its back. The overall body color tends to be anywhere from tan to a grayish tan. It too is a half inch long, just like its common North American cousin. It differs in physical appearance, though, in that it is thicker and is not as shiny. All of its appendages are also considerably longer than the common North American silverfish.
Unlike the common North American though, it prefers temperatures that are warmer and much more humid and chooses harborage within human inhabited structures, including wall voids, basement, and the attic (especially if the house has wooden shingles on the roof). Outside, they are found in the garage and close to the foundation, in flower beds, under the mulch. It prefers the cellulose that is found in paper [6].
- Gray or Giant Silverfish – The Ctenolepisma longicaudata, or gray silverfish, range in size from three quarters of an inch to an inch in length and is the largest silverfish species. They are also known as the long tailed silverfish or giant silverfish. The broad, flat body is a uniform gray color, ranging from light to dark but lacks the silver shimmer or sheen of the common North American silverfish.
The gray silverfish is similar to the four line silverfish in that it prefers warmer temperatures but requires a moist, humid environment. It is typically found in the southern and Midwestern United States, including southern California, choosing to seek harborage in homes. It hides in crevices and cracks all through the house, including garages, closets, kitchens, and storage areas, avoiding light and hiding during the day. It seeks out cellulose from wood based items for food which can include books, tissue, and other paper products as well as beef extract, wheat flour, and other dry foods [7].
- Firebrat – The Thermobia domestica, or firebrat, is darker than the other types of silverfish., often a speckled, dark gray with darker gray, brown, or black patches on a yellowish background on the back. The body is shorter and stouter that other types of silverfish with a broad abdomen that is typically not as long as the thorax. Overall, it is around a half inch in length.
The firebrat prefers hot, humid, dark areas, often found near fireplaces, furnaces, hot water heaters, or boilers. Temperatures above 90 degrees provide the preferred environment. Insulation around heating pipes and hot water pipes are a prime hiding and harborage area, but they will travel to other areas of the house seeking food. Firebrats are primarily nocturnal feeders, choosing products that are high in protein or carbohydrates. This can include paper products, book bindings, glues, and stored foods [8].
Life Cycle of Silverfish
Silverfish go through a type of development known as Incomplete Metamorphosis which has three stages: the egg, nymph, and adult. They have a fairly long lifespan for an insect, anywhere from two to three and a half years, sometimes even longer – as many as eight years. The eggs are yellowish and hatch within 19 to 45 days of being laid. An adult silverfish will lay many eggs during her life span.
When the eggs hatch, the nymphs emerge looking just like the adults, only smaller. They are white, plump, and don’t have any scales but it in some species it may happen as late as the fourth molt. After around two weeks following their first molt they acquire their scales. Silverfish instars reach sexual maturity as adults within three to twenty-four months, depending on species. Throughout their lifespan, a single silverfish will go through around forty-five molts but can be as many as sixty. [9].
The male silverfish does not directly fertilize the female. Courtship and fertilization of the egg or eggs is elaborate. It begins with the male engaging in a mating “dance” to attract the female. Once the female is interested, the male deposits a capsule that contains sperm in a moist area so the capsule doesn’t dry out. The female then picks up the capsule and is fertilized. When silverfish are mating, they may congregate or cluster in areas that are damp and warm. The female lays her eggs in the same area where the silverfish hide during the day. On the average, a clutch contains around 50 eggs, but can reach 200. [10]
What Causes Silverfish?
Silverfish can be very difficult to get rid of so knowing what causes them can help in preventing them. They can be wander into the home from outside, but they are often more likely to be carried in when bringing in boxes, packages, and even food items. In some cases, they are even carried in on building or construction materials. They are attracted to the glue and paper based packaging of the boxes and containers as a food source. They can also arrive in boxes or bags of clothing, rags, or fabric. They consume the carbohydrates in many products including glue and other adhesives, wallpaper, photographs, book bindings, paper, and magazines as well as fabrics like polyester and cotton. In the kitchen, they may be drawn to sugar, flour, and oatmeal, although this is not their preferred food source [11].
Areas that are humid and cluttered provide optimal harborage for silverfish because they need the moist environment and can hide among the clutter during the day. Bathrooms, laundry rooms, and basements that are not clean and dry will attract silverfish and can lead to an infestation. A dirty kitchen, especially with food left out or not adequately cleaned up can also attract the insects. Stacks or boxes of books and magazines that are stored and never moved around can also attract silverfish [12]
Are Silverfish Harmful?
Unlike spiders and mosquitoes, silverfish do not bite and unlike roaches, they pose no risk to human health. They are not dangerous or harmful to humans or pets. They are able to crawl up walls and across ceilings so it is possible for them to drop on humans but they are not attacking or acting in a predatory way. They just fall. [13]
Silverfish are considered nuisance insects, but a large infestation that is left uncontrolled can cause significant damage to property and contaminate food in the home due to their feeding habits. They are drawn to material that contains the carbohydrates called polysaccharides, particularly dextrin and starches. These can be found in adhesives like paste and glue as well as clothing, carpet, hair, coffee sugar, photos, paper, wallpaper, and book bindings. Even household dust and human dandruff can provide a silverfish meal. They will feed on natural fibers like cotton, silk, and linen as well as synthetic fibers like polyester. When their preferred food is scarce, they will consume other materials such as leather and dead insects [14].
This type of damage may not affect the structural integrity of a house or cause disease in humans or pets, but it can be costly nonetheless.
How to get Rid of Silverfish
Silverfish are rarely seen because they are nocturnal, but if an infestation is bad they may be seen during the day. Signs of a silverfish infestation include:
- Finding silverfish, either alive or dead, when they are trapped in the bath tub or sink
- Seeing insects that scurry away quickly when entering a dark room and turning on the light
- Finding silverfish in flour, cereal, or other foods – even sealed products
- Finding damage to books, wall paper, photos, and similar items
- Finding pepper like excrement, yellow stains, or scales on fabrics or paper
These signs are typically found where silverfish are most likely to be such as basements, bathrooms, in walls, under floors, and kitchens, but really anywhere that is warm and damp or moist. To find the areas where they are most prevalent you can put down glue boards or glue traps in various areas around your home (just make sure you keep them out of the reach of pets and children). Monitor the glue boards closely and note where you catch the most silverfish. That is where you should concentrate your pest control efforts.
Once silverfish are in a home it is very difficult to get rid of them. They can become resistant to certain insecticides and it is hard to detect them until the situation has gotten out of control. However, there are some things that will help treat a silverfish infestation [15]:
- Seal all gaps, cracks, and holes that allow the insects access to your home and to the affected area. This will keep them contained in one area so that they are somewhat easier to manage.
- Gather any paper products like books, articles of clothing, or anything else that is made up of materials that silverfish eat, and put it in the freezer for around seven days. Make sure that you wrap the items in plastic and do not remove it until the items have completely thawed. The extreme cold will kill the insects that are in those items.
- Toss out old magazines, newspapers, clothing, and other material that the silverfish may be feeding on.
- Get a dehumidifier or hire a professional service to dry out your home. Silverfish need a moist, humid environment and most species cannot survive in a dry environment.
- Use pest control products either DIY pest control or hire a pest control professional.
Applying pest control products to both the inside, especially along the foundation, and outside along the foundation will help keep silverfish out as well as other household pests.
Many people use home remedies to get rid of silverfish. Some of the more popular methods include:
- Boric acid (Caution if you have pets)
- Cedar shavings
- Cinnamon
- Table salt
- Silica gel
Some people fashion their own silverfish trap. Wrap a mason jar in masking tape to give the silverfish good footing to climb up the side, then place a piece of food like bread, cotton, or wet paper, inside of the jar. They will be able to get into the jar because of the masking tape. However, they are very weak climbers so they will not be able to scale the slippery glass on the inside of the jar to get out [16].
Herbs like basil, eucalyptus, lavender oil, and camphor plant may also be useful. Put the leaves or oils in the areas where the silverfish are most prevalent.
How to Prevent Silverfish
Understanding what draws silverfish into a home will help to prevent them. They enter a structure because they are looking for harborage, food, and water. Target the areas where they are most likely to be found. Take these steps to help prevent a silverfish infestation:
- Seal all possible points of entry including crevices and cracks around windows and walls, and open areas around pipes.
- Don’t allow laundry to sit. Wash as soon as possible so silverfish are not drawn to the damp clothing
- Reduce the moisture in your home by using a dehumidifier.
- Don’t allow your home to become clutter, paying close attention to dark corners and crannies
- Items that are damp from the humidity can be placed in the sun for a while and allowed to dry out.
- Don’t leave boxes of books, clothing, or papers to sit. Move them frequently so they aren’t always sitting in one place
- Keep attics, roof spaces, and basements dry and clean
- Don’t allow magazines, newspapers, and cardboard to pile up in the home
- Clean cabinets, cupboards, pantries, and closets on a regular basis
- Don’t allow food to lay out on the counters or table in the kitchen and don’t leave open food containers in the cabinets and pantry.
- Store food and opened food boxes, bags, or packets in airtight bags or containers
Pest Control for Silverfish
Sometimes a silverfish infestation is just too much for you to handle on your own. Calling a professional pest control company can help you not only get rid of silverfish, but other household pests as well. A pest control technician can inspect your home and offer advice on eliminating silverfish as well as how to keep silverfish out of your home. They have products that are more powerful, but they also know where to apply it for optimal silverfish extermination [17].
There are DIY silverfish control products that work well. If silverfish are already present inside your home, use a residual insecticide and spray it around the inside perimeter of your home. Two products that work exceptionally well for this are LamdaStar UltraCap 9.7 and Cyper WSP. These two products will last for around three months. You should also use a silverfish dust in areas where you have seen silverfish. It is very important that the dust be applied in areas that are not accessible to pets and that humans will not be able to come in contact with it. Two good silverfish dust products are Cimexa Dust and D-Fense Dust.
An aerosol product will allow you to target silverfish where they live and eat. PT 221L Residual Insecticide Aerosol comes with a crack and crevice tip to ensure accurate application in tight spaces, even behind baseboards. Silverfish traps like the Pro-Pest Silverfish Traps can be used around books and stored items to protect them from silverfish attack.
If you choose the DIY silverfish control option, make sure that you wear the recommended safety gear and apparel. Also, carefully follow all product instructions and safety guidelines to ensure a safe and effective application.
Sources:
1.   “Order Zygentoma – Silverfish” BugGuide at Iowa State University Department of
Entomology, (2016), Retrieved October 22, 2016 from http://bugguide.net/node/view/79
2.  “Thysanura: Silverfish/ Firebrats” NC State University General Entomology, (March 28,
2016), Retrieved October 22, 2016 from
https://projects.ncsu.edu/cals/course/ent425/library/compendium/thysanura.html
3.  “Thysanura: silverfish” The Commonwealth Scientific and Industrial Research Organization
(CSIRO), (ND), Retrieved October 22, 2016 from
http://www.ento.csiro.au/education/insects/thysanura.html
4.  “Types of Silverfish” Pets on MOM.ME, (ND), Retrieved October 22, 2016 from
http://animals.mom.me/types-silverfish-7484.html
5.  “Species Lepisma saccharina – Common Silverfish” BugGuide at Iowa State University
Department of Entomology,(2016), Retrieved October 22, 2016 from
http://bugguide.net/node/view/40366
6.  “Species Ctenolepisma lineata – Four Lined Silverfish” BugGuide at Iowa State University
Department of Entomology,(2016), Retrieved October 22, 2016 from
http://bugguide.net/node/view/156092
7.  “Species Ctenolepisma longicaudata – Gray Silverfish” BugGuide at Iowa State University
Department of Entomology, (2016), Retrieved October 22, 2016 from
http://bugguide.net/node/view/151414
8.  “Species Ctenolepisma longicaudata – Gray Silverfish” BugGuide at Iowa State University
Department of Entomology, (2016), Retrieved October 22, 2016 from
http://bugguide.net/node/view/37116
10. “ Silverfish and Firebrats” University of California Agriculture & Natural Resources
(December 2009) Retrieved October 22, 2016 from
http://ipm.ucanr.edu/PMG/PESTNOTES/pn7475.html
12. “ Silverfish and Firebrats” University of California Agriculture & Natural Resources
(December 2009) Retrieved October 22, 2016 from
http://ipm.ucanr.edu/PMG/PESTNOTES/pn7475.html
13. “Silverfish and Firebrats in Homes” University of Minnesota Extension (2016) Retrieved
October 22, 2016 from
http://www.extension.umn.edu/garden/insects/find/silverfish-and-firebrats/
16. “Home Remedies for Silverfish” Home Remedy Hacks (ND) Retrieved October 22, 2016 from
http://www.homeremedyhacks.com/13-helpful-home-remedies-to-get-rid-of-silverfish/
17. “Silverfish Control and Extermination: How to Get Rid of Silverfish” Do It Yourself Pest
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