June 21, 2018
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Silverfish, firebrats could be living silent, hidden lives in your home

Courtesy of Jim Dill
Courtesy of Jim Dill
Silverfish may be living inside any number of Maine homes unnoticed. The invasive insect is happiest where it is warm and humid and presents not danger to humans unless there are allergy issues.
By Julia Bayly, BDN Staff

Of all the pesky insects that can move into a residence, the silverfish just might be the least, well, pesky.

Silverfish (Lepisma saccharina) and their cousins the firebrats (Thermobia domestica) are in Maine, but because of their reclusive, nocturnal lifestyle, people having a population in their homes may not even know it.

“They are a small bug and don’t fly,” according to Dr. Kathy Murray, entomologist with the Maine Department of Agriculture, Conservation and Forestry. “They also can live a very long time. I have read of some that have lived up to 10 years.”

Silverfish and firebrats are recognizable by fishlike, scaly carrot-shaped, wingless body with two long antennae on the heads and three tail-like appendages at the other end of the body. Silverfish have uniformly colored silver bodies while firebrats have mottled gray-brown colored bodies. Both insects can move very fast when disturbed and homeowners often mistake them for cockroaches.

“They like the dark so are active at night,” Murray said. “They can build up slowly over time and in some instances can become quite an infestation.”

The good news, according to Murray, is neither the silverfish nor the firebrat carry disease or even bite.

“There is always a risk of allergy for a small percentage of the human population who may be allergic to these bugs or their droppings,” she said.

Tropical insects, the bugs likely arrived in Maine in shipping boxes or on clothing decades ago and decided to make themselves at home despite the long, cold nontropical winters.

“It’s our own fault they are here,” Murray said. “We carried them in and have given them comfortable places inside to live.”

The bugs like things warm and humid, Murray said.

“Silverfish thrive in basic room-temperatures, around 70 to 80 degrees and they need 70-percent humidity,” she said. “Firebrats like it warmer, around 90 degrees and high humidity.”

In a typical home, those conditions can occur in bathrooms or nooks and crannies adjacent to bathrooms that are often wamer and of higher humidity than other portions of the home.

“Many of us in Maine have wood stoves and home environments where the humidity is too low,” Murray said. “But I’ve seen them in my house occasionally in the bathroom or the room just below the bathroom where the hot water tank is.”

Their favorite diet is anything starchy and sweet — like glue or paste.

So they are attracted to old wallpaper, bindings on old books and cardboard boxes, Murray said.

Finding nibbled, ragged edges on the pages of old books or documents, according to Murray, is a good indicator of of silverfish.

This can potentially make for a serious situation in places like libraries or museums, Murray said.

But according to librarians in central and southern maine, the insects are not an issue.

“I have not come across anyone who has ever seen a silverfish at Portland Public Library,” Emily Bray Levine, the library’s development and external relations director, said.

Levine said by maintaining humidity and temperature levels not conducive for the insects and always unpacking incoming materials outside of the collection storage areas librarians keep the bugs from gaining a foothold.

If someone does think they have silverfish, Murray said the first step is to confirm it with the experts.

“The first thing you want to do is positively identify them,” she said. “So if you see a small, silver, quickly running insect capture it and have someone at [University of Maine] Cooperative Extension identify it.”

From there, the next step is to eliminate any possible food sources and nesting areas.

“Use good sanitation and make sure you have no gaps or cracks they can live in or ‘flaps’ in your wallpaper they can get under,” Murray said “Try and reduce the humidity if you spot them, and if you have the old-style insulation around pipes or in the walls that can have glue, replace it with newer insulation.”

There are commercial products that attract and trap silverfish, Murray said. Crafty homeowners can also go the do-it-yourself route by wrapping an index card with duct tape — sticky side out —and placing a dab of paste made from water, flour and a bit of sugar in the middle of it.

“You really can have them in your home and not even know it,” Murray said. “If you are suspicious, set out one of these traps and wait to see if anything shows up.”

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