SilverfiSh and firebratS Integrated Pest Management In and Around the Home If items on your bookshelf have Although small nymphs (those that are chewed-on pages and bindings, sus- less than 1/8 inch long) lack scales, both pect the look-alike household pests large nymphs and adults have them. If silverfish and firebrats. Both insects you see scales around or beneath dam- have enzymes in their gut that digest aged items, it is a good indication that cellulose, and they choose book cases, these pests are the culprits. The scales closets, and places where books, cloth- are delicate, dustlike, and slightly in- ing, starch, or dry foods are available. candescent in the light, and they stick to most surfaces. Silverfish and firebrats are nocturnal and hide during the day. If the object LIFE CYCLE Figure 1. Adult firebrat (left) and silver- they are hiding beneath is moved, they fish. Eggs of both species are about 1/25 of will dart toward another secluded an inch long. The females lay the eggs place. They come out at night to seek in crevices, on cloth, or buried in food food and water. Both insects prefer or dust. The average clutch contains 50 dry food such as cereals, flour, pasta, eggs, but this can vary from 1 to 200. and pet food; paper with glue or paste; Firebrat eggs hatch in about 14 days and sizing in paper including wall paper; silverfish eggs in about 19 to 32 days. In book bindings; and starch in cloth- colder environments eggs can remain ing. Household dust and debris, dead dormant for up to 6 weeks, hatching as insects, and certain fungi also are im- soon as the temperature rises. portant sources of food. However, they can live for several months without 1 nourishment. Newly hatched nymphs are about /16 of Figure 2. Firebrat adult (left) and an inch long, plump, white, and have nymphal instars, or development stages. Large numbers of these insects can no scales. They acquire their scales invade new homes from surrounding about 12 days after their fourth molt; contact and head wagging, after which wild areas, especially as these areas at that point the firebrat and silverfish the male deposits a protected capsule dry out during the summer. They also look like smaller versions of the adults containing sperm for the female to pick can come in on lumber, wallboard, and and gradually grow in size until they up. To keep the capsule from drying out, similar products. Freshly laid concrete reach maturity (Fig. 2). Unlike other in- males often will lay it on a moist surface, and green lumber supply humidity, sects, firebrats and silverfish molt con- so it is common to see adult insects clus- while wallpaper paste provides food. tinuously throughout their life, passing through 45 to 60 instars or develop- tered around damp areas when mating. IDENTIFICATION ment stages. Firebrats live about 2 years Firebrats and silverfish tend to crowd and silverfish about 3 years. together in a central hiding place during The common silverfish, Lepisma sac- the day to rest, and it is here where the charina, is shiny, silver or pearl gray, When the temperature is below 50°F, females often lay their eggs. Both sexes 1 and about /2 inch long, although it can firebrats can take as long as 300 days produce pheromones, or chemicals, that grow as long as 3/4 inch. The common and silverfish as long as 500 days to initiate these aggregations, and when firebrat, Thermobia domestica, is shiny, a develop into adults. When it is above these insects crowd together, it helps mottled gray or brown, and about 1/2 75°F, it can take firebrats as few as 40 regulate the temperature and humidity inch long. Adults of both species are days and silverfish as little as 60 days around the eggs and young nymphs. slender, wingless, soft-bodied insects to develop into adults. with 2 long, slender antennae (Fig. 1). Silverfish live and develop in damp, Their bodies taper gradually from front Adults have an interesting courtship warm places, preferring areas such as to rear to 3 long, thin, taillike append- in which males attract females with a laundry rooms that are 71º to 90ºF. At ages. mating dance that includes antennae higher temperatures, the relative humid- EST OTES Publication 7475 PUniversity of California N Statewide Integrated Pest Management Program Agriculture and Natural Resources December 2009 December 2009 Silverfish and Firebrats ity must be above 75%. As their common repair leaks and drips in plumbing. names implies, firebrats thrive best in Silverfish require a lot of moisture, so very warm, dry places with a relative using dehumidifiers in closed spaces humidity as low as 30% and tempera- can help discourage these pests. Ven- tures above 90ºF, with the optimum tilation from fans can reduce relative being 98º to 102ºF. However, they can humidity to a point that is intolerable survive at temperatures ranging from to silverfish. Because collections of freezing to well above 100ºF. You can magazines, papers, and books provide find them around ovens, heating units, food and harborage, occasionally move fireplaces, hot water pipes, attics dur- these items around in your bookcase. ing the summer, and the furnace dur- Keep food in containers with tight lids, Figure 3. Firebrat damage to paper ing winter. In apartments and homes, especially dry, processed items. includes feeding (large, dark spots), this insect crawls along pipelines and grazing (gray areas and missing letters), Chemical Control discoloration due to fungi (dark brown through openings in walls or floors from spots), and scales and fecal debris (light- one level to another. Sometimes you’ll Hundreds of commercially available er brown spots). see these pests in your bathtub or sink. insecticides list firebrats and silverfish Even though they can’t crawl up through on their labels. However, most of these (including certain boric acid or silica the drain, if they fall in they can’t climb products haven’t been adequately test- gel products) are very effective against up the slippery sides to escape. ed. Insecticides aren’t required to con- firebrats and silverfish if you apply the trol light infestations or an occasional product directly on pests. Labels limit DAMAGE insect; these can be managed by reduc- use of some inorganic dust products in ing water sources and through physi- Firebrats and silverfish have very weak open areas. Be sure to check the label. mandibles, or jaws, which causes them cal control. Reserve chemical use for large infestations. Insecticides won’t be to scrape, instead of bite, the surface of Apply dusts with a bulb duster, pow- effective unless you also remove the paper (Fig. 3). Page discoloration often der blower, or a plastic squeeze bottle moisture, food, and hiding places that occurs because of the fungi associated to leave a fine layer of the material in allow these pests to thrive. with their feeding damage. On paper the area you are treating. If the layer is and fabrics feeding usually begins in too thick, the surface will be slippery. If you have an infestation, household one area and spreads as unconnected, Apply into areas as described above irregularly shaped holes. sprays containing synergized pyrethrin and pyrethroids such as bifenthrin, cy- for sprays, paying special attention to cracks, crevices, and wall voids that MANAGEMENT fluthrin, tetramethrin, and phenothrin should kill firebrats and silverfish on serve as congregation sites. Since firebrats and silverfish are noc- contact and provide some residual activ- turnal, you usually won’t see them. To ity. Direct small amounts of these aerosol Inorganic dusts such as silica gel and detect and monitor infestations, use or liquid sprays into cracks and crevices pyrethrin (e.g. Drione) and diatoma- cockroach sticky traps. You also can use in doors and window casings, along edg- ceous earth (e.g. Perma-Guard) remain small, glass jars covered on the outside es and intersections such as baseboards, effective indefinitely in dry locations. with masking tape. The insects climb in closets, bookcases, and places where If dust deposits get wet and then dry, up the tape, fall into the jars, and can’t pipes go through walls, and into voids they will cake, making them difficult climb back up the slick sides. Place and other suitable, dark hiding places. for insects to pick up. You might need these traps or jars in corners and along Because some sprays have oil-solution to periodically re-treat moist areas. edges where foraging is likely. Because bases, don’t apply them near electric Follow label directions. Foggers aren’t these insects can travel long distances motors, gas pilot flames, or other places recom mended to treat silverfish and while looking for food, it can be diffi- where they can start fires. Follow label firebrat infestations. cult to pinpoint the infestation source. directions. Don’t allow these materials to get into sinks, drains, water, or food. A properly and thoroughly applied To prevent silverfish and firebrat infes- insecticide will show results in a few tations, keep basements, laundry rooms, A variety of commercial baits and dusts weeks. If control doesn’t occur in 2 or 3 and bathrooms—especially shower also are available. However, baits aren’t weeks, silverfish or firebrats probably stalls—clean and dry. Household dust very successful in treating silverfish are coming from untreated areas and and debris are important sources of and firebrats, because they tend not secluded harborages. Seek out these food, so routine cleaning will help to feed on them. Similarly, several of areas for treatment, and eliminate wa- provide effective control.