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Educational Resource Guide #5Silverfish and Firebrats

Silverfish and Firebrats
by Barb Ogg, Extension Educator

Silverfish and firebrats cause damage in homes by eating foods and other materials that are high in protein, sugar, or starch. They eat cereals, moist wheat flour, any paper on which there is glue or paste, sizing in paper (including wallpaper) and book bindings, starch in clothing, and rayon fabrics.  

Line drawing - silverfish Firebrat - Click for Larger Image
Silverfish Firebrat

Description and Habits:  Both of these insects are slender, wingless, and covered with scales. Adults are one-third to one-half inch long. Silverfish are shiny and silver or pearl gray in color; firebrats are mottled gray. The young insects look like the adults except that they are smaller. Both insects have two long, slender feelers at their head end, and three long, tail-like appendages at the hind end.

Silverfish and firebrats are very common in homes throughout the United States. Both are active at night, hide during the day, and avoid direct sunlight. When objects under which they are hiding are moved, they dart out and seek other hiding places. 

The silverfish lives and develops in dark, damp, cool places, especially basements. Large numbers may be found in new buildings in which the masonry is still damp. Because silverfish require and seek a moisture source, they are frequently found trapped in sinks and bathtubs. However, they may be found in bookcases, around closet shelves, behind baseboards, and behind window and door frames. Silverfish are often brought into new homes in cardboard cartons, books, and papers from infested sites. 

In contrast, the firebrat lives and develops in hot, dark places: for example, in attics, around furnaces, ovens, and fireplaces, and in insulation around hot water and heat pipes. It prefers areas where the temperature is 90o F and above. Temperatures below 32o F and above 112o F readily kill immature stages of this pest. 


For control of silverfish and firebrats, three non-chemical control tactics should be considered: 

1. Change the physical environment in the immediate ares of infestation. For example, controlling or eliminating moisture (e.g. leaky plumbing, around laundry areas, etc.) where a silverfish population is thriving can be quite effective in significantly reducing the level of infestation.

2. Reduce the potential sites of harborage. Seal obvious and easily accessible cracks and crevices. Do not leave silverfish and firebrats preferred places to hide and breed. 

3. Remove potential food supplies, specifically paper, book bindings, starched linens, and organic debris. If these materials cannot be secured in tightly sealed containers or cabinets, make sure your pest control application cuts off access of these pests to potential food sources. 



Although liquid, dust or bait formulations can be used for silverfish and firebrat control, liquids are usually preferred in exposed areas of the home where dusts or baits may present a hazard to homeowners or pets. Currently registered liquid insecticides and their rates of use for silverfish and firebrat control include the following: propoxur, chlorpyrifos, bendiocarb. The effectiveness of residual sprays often can be enhanced by using them in conjunction with short-lived contact sprays, such as pyrethrins (resmethrin, allethrin). Pyrethrins irritate the insect which causes them to run over an area on which a residual spray has been applied. Pyrethrin aerosols are conveniently available in grocery stores. Residual insecticides usually provide 15-45 days of control and should be applied to the areas where the silverfish and firebrats are most commonly seen. Because both insects prefer to hide or rest where there are tight cracks or crevices, particular attention should be given to injecting small amounts of insecticide into cracks and crevices formed by shelving, loose moldings, or floor tiles. Spray around baseboards, door and window casings, bookcases, shelving, closets, and in other storage areas, and places where pipes go through walls or floors. Spraying only the warmer parts of the building is usually sufficient to control firebrats. 


Dusts provide exceptional control of silverfish and firebrats, although they are more visible and can move from the original site of application. As a consequence, dusts can be used effectively in attics, dry crawl spaces, basements, and other places where their use is not potentially hazardous. Commonly used dusts currently registered for silverfish and firebrat control are insecticides such as amorphous silica gel, boric acid, bendiocarb, and diatomaceous earth. Pyrethrin dusts can be used but have shorter residual activity. Dusts are best applied with a hand duster, although boric acid dust can be obtained in an aerosol formulation. Inject dusts into cracks, or spread a thin film wherever the appearance of the deposit will not be objectionable.

Regulations governing the use of pesticides are subject to constant change. Therefore, it is important to use the insecticide only as specified on the label.  (updated March 27, 2001)

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