A common question any homeowner may ask is: what are silverfish, and why do I have them? These pests flourish in humid climates. You will likely find them hiding in your bathrooms, kitchens, basements, or sheds. Sadly, having silverfish is about as common as having roaches or ants. You can lead as clean a life as possible, but you still may get them. It does help to keep a clean house; do not leave crumbs lying about or let trash pile up. 

Adult silverfish
silverfish. Insect Lepisma saccharina, Thermobia domestica in normal habitat

Silverfish can live for up to 3 years. Many homeowners don’t even realize they are infested with them until they see them. This pest is nocturnal and prefers to stay out of the sight of humans. When they are spotted, it is when the homeowner sees them scurrying back behind a baseboard in the bathroom. They are also commonly found in sinks, tubs, and especially near cardboard.

Silverfish are exponential reproducers. Females can lay 1-3 eggs per day, though it does take 3-4 months for them to develop. Silverfish are sometimes called bristletails because of the three long appendages on the rear of their body. They prefer warm, humid climates, from 72-90 degrees and 50-75% relative humidity. Because of this, silverfish tend to flourish in sub-tropical climates.

What Are Silverfish?

The term “silverfish” comes from the coloring and shape of this common pest species. They are silver or gray with glistening scales, much like a fish. Silverfish also have a “wiggly walk,” likening them to fish swimming through water. They have long tapered bodies and are generally only about a 1/3” in size. Silverfish is a common name for several species in the Zygentoma order. But are more commonly associated with the species Lepisma saccharina. They are insects with six legs and no wings, but they do have three posterior appendages, one that extends straight out, two that jut out from the left and right sides. This insect can regenerate some body parts, including antennae, in about 2-4 weeks. 

Silverfish are a primitive order of insects and not very evolved. Like humans, immature insects resemble their adult versions. However, these insects hatch from eggs and are not live births. These insects molt continuously throughout their lives, but it only takes around seven moltings for them to reach their full adult stage. Silverfish have been recorded as molting up to 66 times in a lifetime, which can last up to 4 years. 

Many homeowners don’t realize they have silverfish because these pests are nocturnal creatures. Silverfish have often become extremely problematic in museums and libraries due to strict climate controls and an abundance of preferred feeding materials. Silverfish are fast, and when disturbed, they will quickly try to conceal themselves, making them quite challenging to catch and detect. 

The most likely places you’ll find silverfish damage are in kitchens, bathrooms, attics, garages, and sheds. These areas tend to have higher humidity levels and plenty of feeding materials for the pests. Shake roofs are near perfect breeding grounds for this insect, and there is an abundance of moisture and dead insects for feeding.  It is easy for them to make their way through these roofs and into the structure where they set up habitat in wall voids and subflooring. 

What do silverfish eat?

Silverfish have a preference for starchy and sweet substances. They mainly feed on proteins and carbohydrates such as flour and rolled oats. One of their favorite meals is dried beef. These pests are also cannibalistic feeding off their dead and dying kin. 

Silverfish are incredibly destructive. They can wreak havoc on paper, cardboard boxes, book bindings,  and carpet glue costing homeowners the renovation and replacement costs. They will also dine on wallpaper, plaster, some paints, and even photographs. Silverfish are mainly a nuisance pest, though they can cause damage by chewing holes in clothing and upholstery. 

How do I know if I have silverfish?

If you stumble across some feeding marks, you may have a silverfish problem. Check for holes in wallpapers, or notches along edges. Sometimes homeowners will find yellow stains or shed scales. If the infestation is particularly bad, they may discover excrement, which looks like black pepper. Many people notice silverfish scattering when they turn on the lights in the bathroom. Sometimes they can be found in sinks or tubs. Some homeowners will descend from their attic to find a silverfish scurrying behind crown moldings or into recessed lighting fixtures. If you do suspect you might have silverfish and have found evidence, call your local pest control professional to do an inspection.   

How can I get rid of silverfish?

There are many methods of “natural” silverfish removal methods. It has been said that these pests dislike strong odors. To discourage this pest from taking up residence in your kitchen cabinets, many DIY sites will offer up various solutions. Typical suggestions are cinnamon sticks, bay leaves, cloves, or dried rosemary. Japanese Cedar oil will also be cited as an effective method of deterring silverfish. However, all these methods manage to do is deter the silverfish to another location in your home. Once they have found ample feeding grounds and satisfactory habitat, it is difficult to eradicate them without tougher methods. 

If you want to try home methods before calling in a professional, methods utilizing boric acid might work. None of these methods should be used if you have children or pets in the home. Boric acid may be organic, but can be extremely harmful if ingested. The first simple method is to sprinkle boric acid in the path of the silverfish. Hopefully, the pests will consume it and suffer its toxic effects. Boric acid will also dehydrate the exoskeleton if the silverfish shimmies across it. The next method is for targeting the habitat where silverfish are. Mix the boric acid with water and spray it into cracks and crevices where you believe the silverfish might be living. Finally, you can make a paste of flour, water, and boric acid, spread it on an index card then set it out for the silverfish to eat. It should be noted that none of these methods will work on the eggs of the silverfish, so prepare for the long haul to completely eradicate the silverfish community in your walls. 

Diatomaceous Earth is another standard DIY method for eradicating your home of numerous pests including, fleas, roaches, and silverfish. Any insect with an exoskeleton will be impacted by using diatomaceous earth. If you haven’t heard of it, diatomaceous earth is formed from the fossil remains of diatoms, which are single-celled alga with a wall of silica. When crushed and spread around the home, insects with an exoskeleton will get scrapes in the shell and eventually dehydrate. This method is much safer for use around children and pets. Diatomaceous earth is even available in food-grade forms that will work the same way.

Most professionals will use chemicals to eradicate silverfish populations. The most common is pyrethrin, derived from chrysanthemums and is a common ingredient in flea repellant collars. This chemical is not entirely harmless to humans and pets, but is one of the least toxic pesticides available. The other pesticide commonly used is propoxur, which is slightly more toxic to humans and pets. Common side effects of this chemical are nausea, blurred vision, sweating, and vomiting. The use of propoxur does not harm most people. In addition to the formerly mentioned methods of silverfish extermination, none of these methods will eradicate the silverfish eggs. Once you have a silverfish infestation, it is crucial to keep on top of treatments until all are eliminated, or they will return. 

How can I prevent them?

So what can a homeowner do to prevent silverfish in the first place? Some simple methods are general tips for the discouragement of many pests. Keeping a clean house is always the first step in pest prevention. Make sure to keep counters and floors free from food residue like crumbs by making a regular habit of cleaning after meal preparation. Since silverfish like to eat the glue and cardboard of stock items, it is best to remove these types of foods from their original containers. Consider storing them in reusable plastic containers with resealable lids. This method is also a great tip for preventing two other common household pests, ants, and cockroaches.

Always make sure to stay on top of leaks in your home. Besides the cost-benefit to this practice, this will help to prevent humidity seeking insects from making their way into your home. Any puddles of standing water will attract silverfish and can also serve as a mosquito breeding ground, especially outdoors. Remove debris from outside areas to prevent silverfish from invading sheds, garages, and other outdoor structures. Do not let trash pile up inside or outside your home. Make sure to take your trash out to receptacles with lids outside to prevent pests from invading.

Regular vacuuming of your home with a HEPA filter will remove dust, debris, and many creepy crawlies. Run the hose attachment along baseboards to remove insects and their eggs from hiding spots behind your walls. Also, remember to clean out behind your appliances, especially in areas where pests are prone to congregate like kitchens and bathrooms. If you can get behind it, clean it. Do the best you can with sealing crevices along sinks, tubs, and other household places where water flows. 

Lastly, control the humidity inside your home to the best of your ability. In Florida, many homes have central air conditioning, which does a good job, but may not be available in older homes. Use a dehumidifier if you live in a home that is especially prone to higher humidity levels. Keeping a clean house and utilizing cautionary measures will help keep the populations of any problem pest in check. 

Resources:

 (2008) Silverfish (Zygentoma). In: Capinera J.L. (eds) Encyclopedia of Entomology. Springer, Dordrecht

http://entnemdept.ufl.edu/creatures/URBAN/silverfish.HTM

https://www.pestworld.org/pest-guide/occasional-invaders/silverfish/

https://edis.ifas.ufl.edu/ig094

https://www.epa.gov/sites/production/files/2016-09/documents/propoxur.pdf

Dusty Showers has been in the urban nuisance wildlife and pest control field since 1993. Taught by Garon Fyffe, a pioneer in humane nuisance wildlife management, Dusty has a passion for finding humane solutions to human & wildlife conflicts. Dusty was the only individual invited by the Florida Fish & Wildlife Commission in the lat 1990's to help write legislation for legal protection of Florida bats. With an instinct for solving wildlife, Dusty found pest control to be an easy "add-on interest". Dusty started his first business "Animal Instincts Wildlife & Pest Management" in the Tampa Bay, Florida area in 1995. Eventually selling Animal Instincts in 2002, Dusty went on to start Creepy Creatures Termite and Pest Control in 2009, which he still owns and operates today in Palm Harbor, Florida.