You Little Firebrat!

With the extreme heat wave in Eastern Nebraska lately, firebrats are literally coming out of the woodwork. One of the most common comments I get from clients who show up at our office with a mystery specimen is:

“I never have pests, but I found this…”

 Most people have heard of silverfish, but have you heard of firebrats?

Firebrat on the wall

The firebrat is an indoor pest commonly found in areas of high heat and humidity. It is a mottled brown-gray color, with long antennae and 3 tail-like appendages. Photo by Jody Green, Nebraskas Extension in Lancaster County.

Description of the Pest

Silverfish and firebrats look similar in shape, size (¼ to ½ inch long) and number of appendages. Collectively, they belong to a group of insects called bristletails (Order: Thysanura). They are both wingless, soft-bodied, carrot-shaped insects with two thin antennae on the head and three tail-like appendages extending from their tapered abdomen. The difference between silverfish and firebrats include the stoutness of the bodies and the color of scales. Firebrats appear stouter with a mottled brown-gray color, and silverfish are narrower in the abdomen with powdery, dull, silver scales. As their name implies, they move like a fish.

Silverfish

Silverfish and firebrat have similar shapes, but the silverfish has silver scales and a narrower tail. (Photo: Wayne Ohnesorg, Nebraska Extension)

Biology and Behavior of Bristletails

Silverfish prefer damp, warm places like basements, bathrooms and laundry rooms that range from 71°F to 90°F. Firebrats, as their name implies, like it hot, like 98°F to 102°F hot! They thrive in dry, dark places, especially when temperatures rise over 90°F. They are commonly found in attics, furnace rooms, near hot water pipes and in roofing shingles. They are often associated with cedar shake roofs in Nebraska and crawl out through light fixtures, ceiling fan and vents. Even though firebrats are known for their affinity for heat, they can survive a wide temperature range, which includes freezing temperatures.

Silverfish and firebrats feed on carbohydrates, anything with high protein and high sugar content. These starchy materials include wallpaper glue, fabrics (silk, cotton, rayon), cereals, plaster, cardboard carpet and other cellulose or paper products. They do most of their feeding at night, but can be found during the day when the get trapped in sinks, bathtubs or drawers when surfaces are too slippery to escape. Bristletails have weak jaws and their mandibles can only scrape the surfaces of their food, leaving characteristic damage on items.

Firebrat on a blanket

Firebrats feed on starchy materials, including paper products, cereals, books and fabrics. This firebrat is on a blanket. (Photo: Jim Kalisch, UNL Department of Entomology)

Life Cycle: Forever Molting

Unlike other insects that have a fixed number of molts until maturity, silverfish and firebrats molt continuously throughout their lifetime, shedding the exoskeleton over 50 times. Nymphs and adults resemble one another, but younger nymphs lack scales. Female firebrats lay an average of 50 eggs in crevices, and under optimal temperature and humidity hatch in 14 days. The lifespan of a firebrat is 2 years. Silverfish require more days to reach maturity and live about 3 years.

The Good, Bad and Ugly

The Good: Silverfish and firebrats do not bite or cause harm to humans. They are not of medical importance and will not ruin the structural integrity of your home.

The Bad:  They can cause damage to old collections and sentimental artifacts, particularly paper, magazines, books and photographs. They are also prey for many house-dwelling predators such as centipedes and spiders, including the brown recluse spider.

The Ugly: They leave small holes in objects and leave yellow stains. There is fungus associated with their feeding which can also discolor paper products. In areas with high infestations, bristletails can leave dust-like scales on surfaces from their bodies.

Silverfish damage on the hard cover books

Silverfish damage to book covers. (Photo: Jim Kalisch, UNL Department of Entomology)

Clean Homes Can Have Firebrats

The best way to eliminate silverfish and firebrats is to modify the environment. To make the home less attractive find ways to reduce the humidity fix moisture problems or plumbing leaks, increase ventilation and air circulation, seal harborage areas like cracks and crevices, and do your best to eliminate food sources. Consider running a dehumidifier or fan in the bathroom, wiping water off the counter and sink after use, and squeegeeing the shower walls. Store paper recyclables (magazines, newspapers) in dry locations in the garage before pick up.

On the exterior of the premises, trim trees close to the house and manage the vegetation and leaf litter along the perimeter. Many nuisance pests come in from outdoors, and silverfish have been associated with cedar shake roofs.

Some pet cages contain newspaper for bedding, which could also provide food and harborage for silverfish and firebrat, change bedding often and do not allow paper to stay damp for long.

The use of sticky traps can help determine the population size and pinpoint the location of the greatest number of insect pests. To remove silverfish or firebrats from ceilings, walls and floors, use a vacuum. To protect important products like paper products, sentimental articles, photographs, linens and foodstuff, store them inside airtight containers in dry locations.

Firebrat damage to fabric

Firebrat damage to woolen suit coat. (Photo: Jim Kalisch, UNL Department of Entomology)

Chemical Control for Silverfish and Firebrats

Because silverfish and firebrats are often found harboring in attics, I would recommend hiring a pest management professional to treat those hard-to-reach areas that require climbing a ladder, enclosed spaces and balancing on rafters. Do not risk your health and safety to battle bristletails. Safety first!

There are many insecticides labeled for silverfish (and firebrats) and can be used in heavy, long-term infestations. Because silverfish and firebrats often hide in wall voids and crevices, it would be best to find a formulation and method to apply it directly where they harbor. There are a few commercially available bait formations for silverfish and firebrats. The concept behind baiting is to attract the pest to a food source that is both palatable and toxic. Baits can be in applied as an impregnated paper attractant, a paste or granular form. Controlling silverfish and firebrats with baits may be difficult due to repellency of the ingredients in the bait, the option of other more desirable food sources and because they can survive extended periods without feeding. Dust formulations such as silica gel or diatomaceous earth can be applied as a light powder into dry locations where silverfish and firebrats hide. Dusts are insecticides that work by desiccating or dehydrating the insect by compromising their exoskeleton so they die. As a reminder, do not treat the sinks, bathtubs drains or water. Always read the label and follow the application instructions and safety precautions.

Confessions of an Extension Entomologist: I’ve found a couple firebrats since moving into my new/old/renovated house in June. The attic which currently lacks insulation, was extremely hot (over 95ºF) and I found one near the recessed lighting cans on the ceiling. The second one was running around in the drawer that we keep our drinking glasses. I admit, there may have been a time (or two or three) that I’ve put a glass from the dishwasher into the drawer, and they haven’t been completely dry. That moisture, darkness and the shelter of my plastic drawer liners create a nice habitat for these little firebrats. We’ve since cleaned our vents, adjusted our ventilation in the house, sealed some cracks, and I make sure the dishes are dry.

Keep calm and respect the critters,

Jody

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