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Fun Facts About Museum Pests: Silverfish
The bane of archives, libraries, and paper-based collections everywhere: the silverfish!
In previous installations of Fun Facts About Museum Pests, I discussed carpet beetles and clothes moths, two common museum pests with similar life cycles (their larval forms cause the most damage to collections) and food preferences (proteins). Silverfish are completely different: they don’t have a larval stage. Instead, their young predecessors are called “nymphs” and they just look like smaller, translucent versions of adult silverfish. And rather than proteins, they like to munch on starches.
Identification
Silverfish are a wingless insect that can be up to 10-15 mm in length. Their bodies are easily recognizable as they are “carrot-shaped” and covered in silver or gray scales, with long antennae and three long tail-like bristles.
Adult gray silverfish (Ctenolepisma longicaudata); Pest and Diseases Image Library, Bugwood.org
Damage to cardboard by small blue silverfish (Lepisma saccharina); Clemson University - USDA Cooperative Extension Slide Series, Bugwood.org
Behaviour
Silverfish are omnivorous and will eat both cellulose and protein materials. They are especially fond of the sizing of paper, and the glue and paste in book bindings. They are known to enjoy eating wallpaper, and the glue holding it to the wall. They will eat any material that has been treated with starch, gelatin, or organic dyes, including textiles like silk and cotton. They also eat microscopic mold on the surface of items.
Silverfish have weak mandibles and feed on materials by scraping at the surface. This causes damage that appears as irregular thin patches on the surface, occasionally breaking all the way through to leave oddly-shaped holes with ragged edges. They will sometimes eat away preferentially at organic dyes, leaving an interesting trail of damage on labels, prints, or wallpaper, with some colors eaten first.
Silverfish thrive in cool, damp, dark environments. Finding silverfish is a strong indicator that you have moisture problems - they’re most likely to be found in attics, basements, bathrooms, and kitchens. Where there are silverfish, often there is also mold.
You’re unlikely to see silverfish scampering across the floor. They prefer to lurk in cracks and crevices and behind walls. They’re nocturnal, and hide during the day or when the lights are on. If you come across silverfish at random in daylight, it means you could have a big infestation somewhere in your building.
Silverfish live as long as three years and will molt up to 50 times. They can live for nearly a year without feeding! Eggs will hatch after about a month, and the young spend about 3 months as nymphs before becoming adults. They multiply quickly!
Treatment
Use sticky traps to monitor for a silverfish infestation. They can help you locate where the pests are entering an area, and help you keep track of the success of your preventative measures. You can also identify an infestation by looking for small dark frass, yellow stains, scales and the telltale signs of damage on paper.
Because silverfish like the damp, the best way to rid yourself of a silverfish problem is to dry out your environment. If you can’t eliminate moisture, move your collections into a drier space to protect them. Keeping the room at a temperature below 60 degrees will also help slow silverfish down.
You can make it more difficult for silverfish to access collections items by keeping everything up off the floor on shelving, and by controlling food sources by removing cardboard boxes and paper products that are not part of the collection.
Use freezing treatment to kill silverfish and their eggs on artifacts. It can be difficult to completely eliminate a silverfish infestation. If monitoring indicates that you still have an issue despite taking preventative measures in your environment, you should work with a conservator and a pest management expert. Never put pesticides directly on your collection.
Silverfish in his Christmas best. Art by James Hales, photo by Megan Narvey.
I’ve been somewhat fond of silverfish ever since one of my grad school professors drew a picture of one in its “Christmas best” during a lesson. It's just so dapper!
Learn more about silverfish at these links:
Pest Fact Sheet: Silverfish (PDF)
Museum Pests: Silverfish (PDF)
Silverfish and Firebrat Diagnostics
Managing Pests in Paper-Based Collections (PDF)
NEDCC - Integrated Pest Management
NPS Museum Handbook Chapter 5: Biological Infestations (PDF)