Silverfish Vs. Firebrats

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April 1, 1999
Occasional Invaders

Q: I am not sure of the difference between silverfish and firebrats. Is this a case where the same insect has two different names or are they two different pests? Is control the same or is there some difference? (L.C.)

A: Both silverfish and firebrats belong to the same insect order, Thysanura. They are also typically placed in the same family. Depending on whom you consult, there may be as many as eight to 10 different species of silverfish in North America and only one species of firebrat. Beyond that there are both similarities and differences in their appearance and behavior.

At first glance, both silverfish and firebrats appear similar. On closer inspection, firebrats tend to have longer antennae that often extend past the tip of the abdomen. Also, firebrats tend to be a mottled gray color with patches of dark gray and lighter silver over the dorsal surface of the body. Silverfish tend to be uniformly gray or silver in color, although there is at least one species with dark lines extending down the length of its back.

Both silverfish and firebrats are often referred to by another common name, bristletails. Obviously, this name refers to the long appendages attached to the tip of the abdomen. If you are interested in definitely identifying either firebrats or silverfish, you may want to refer to an excellent key found in the chapter on these two insects in the 8th edition of the Handbook of Pest Control.

Both silverfish and firebrats tend to prefer warm, moist areas. However, this may be misleading at times. While an area may appear warm (such as a furnace or heater room), there may not be an obvious source of moisture. In my experience, both silverfish and firebrats generally have a very low moisture requirement and can easily find moisture sources such as floor drains, condensate pans and wet walls. Both insects are most commonly indoors, however, I’ve found that in the South, both can occur in the peridomestic environment. Clutter in garages and storage sheds are typical locations for these pests. I’ve also found firebrats living under tree bark in firewood piles outdoors.

Both insects have chewing mouthparts and can damage a wide variety of materials. They both appear to have an affinity for starches and animal proteins. Typically we find silverfish feeding on paper and some cloth materials. It should be noted that both silverfish and firebrats are extremely resistant to starvation and can exist without feeding for long periods of time. Additionally, both insects are relatively long-lived. Life spans may exceed three years.

Generally speaking, the control procedure used for German or brown-banded cockroaches in homes will also be effective for silverfish and most firebrat infestations. There is some indication that silverfish tend to roam more widely in search of food and harborage and that firebrats tend to be more localized in their distribution. Also, remember that under some circumstances, firebrats exist in the near outdoor environment and may be brought into a structure in infested materials.

If the infestation is severe and of long duration, a number of non-chemical steps may be taken to reduce the suitability of the environment for these two insects. Generally, removing or reducing clutter and other forms of food, as well as reducing the availability of moisture to include reducing humidity, has been effective in managing these pests. In most cases, though, to achieve a quick resolution to a localized silverfish or firebrat infestation you will need to focus on treating cracks and crevices, as well as void areas in and adjacent to the environment where the pests were seen. Most residual insecticides will be effective against these pests. It is important also to remember that the use of dusts, including inorganic materials, can provide not only immediate relief but also long-term control. Currently, I don’t have enough information to determine whether or not any of the baits used in cockroach control will also be effective on silverfish. Perhaps that will be looked into in the near future.

Jeffrey Tucker is president of Entomology Associates, Houston. Questions can be sent to Questions & Answers, c/o Entomology Associates, P.O. Box 70375, Houston TX 77270, or faxed to 713/681-9069.