If you've ever gone through old boxes in your attic and spotted some silverfish, you might be grossed out. But why are these insects there in the first place? And are they dangerous?
You may be happy to know that they don't do nearly the same damage as other pests, like termites, and they're not harmful to humans. "Silverfish like to chew on things, especially paper or fabrics that may have starch or sugar residues embedded in them, such as wallpaper with the starch-based glue that was used to hold it in place," says Doug Webb, manager of technical services for pest control company Terminix in an email. "Another example would be clothing that has been starched. Silverfish chew on the fabric to get the starch, but in the process damage the fabric."
Silverfish were once often seen in books (since books are bound with glue), but not so much now. Years ago, most glues were produced using animal byproducts or other natural materials that contained a high starch, sugar or animal protein content. "Newer types of glue are products of modern chemistry and would be of no interest to silverfish because they have no nutritional value," Webb explains.
A Very Ancient Insect
Silverfish (Lepisma saccharina) have been scuttling around the world for more than 400 million years and remain pretty much the same as in their pre-dinosaur days. "Other than size, they have evolved very little in that time," emails Scot Hodges A.C.E., vice president of technical services with Arrow Exterminators. "They are impressive survivors which may explain why they have had little need to evolve. Some sources claim they can live up to 6 months without food or water so long as they have one or the other."
Appropriately, silverfish are prehistoric in appearance. Their build is skinny, with a round head to a pointy abdomen region. In fact, they are often referred to as "carrot-like" in shape. They are shiny and gray, covered in tiny scales, which makes them look silver. But that's not the only thing that likens them to fish.
"The common name 'silverfish' comes from the fact that they are gray to silver in color and wiggle as they run in a manner that looks like a fish swimming," says Webb. They shed their skins well into adult life (you may have seen their scales lurking in your house.)
Getting Rid of Silverfish
Unlike most of the world's other insects, silverfish don't seem to have a lot of redeeming qualities. "They do not serve any beneficial purpose to man that I am aware of," Webb says. So you shouldn't fret about getting rid of them.
Silverfish aren't exactly begging to be found, as they prefer areas that people rarely enter. "They can be found in any part of the home, but seem to prefer dark undisturbed places," Hodges explains, noting that dark, high-humidity spots such as crawl spaces, unfinished basements and attics are prime silverfish real estate. "These areas are suitable environments for them and are also where homeowners keep stored items that provide them harborage and food." They tend to enter homes to avoid weather extremes and wind up staying because the atmosphere is just so hospitable.
These nocturnal creatures generally take quite a long time to reproduce enough to reach infestation status. If you don't yet have a silverfish problem, keep it that way by minimizing your junk. "The key to control is to limit or eliminate harborage," Hodges says. "Large infestations are often linked to stored items and clutter."
If you do happen upon some silverfish it's not a disgusting cleanup. "Often, vacuuming them is the fastest and easiest way to get rid of them," emails Frank Meek, technical services manager with pest control company Orkin.
He also suggests inspecting your home once per year at minimum to identify any spots where pests can enter. "If you store items in your basement or attic, make sure they are in hard plastic containers, not cardboard boxes. When moving storage items, inspect them first and make sure you aren't transporting insects into a new space," he says.
Webb's team at Terminix generally identifies any food sources that silverfish find irresistible, like starch residue on the floor of a utility room or food spillage from items like grains, pasta and cereal. "It is also important to reduce humidity in higher humidity areas within the home by circulating the air with fans, using dehumidifiers or other moisture reduction methods."
If silverfish have already gotten out of control, Meek says to seek professional help. "If you see a sign of a silverfish infestation, contact your local pest control professional who will assess the situation within your home and determine the most effective methods of extermination for your specific problem."