UC RIVERSIDE
ENTOMOLOGY

Contents of Chapter

• Carpet beetles (Dermestidae)
• Beetle Species List
• Clothes Moths (Tineidae)
• Moth Species List
• Control of Carpet Beetles and Clothes Moths
  • Insectproofing Agents
• Silverfish (Thysanura: Lepismatidae)
• Silverfish Species List
• Control of Silverfish
• Comparison of Destructiveness of Fabric-Feeding Insects
• Miscellaneous Pests

The widespread use of wool and other animal hair in clothing, carpeting, furniture, and other household materials gives insects the potential for being of great economic importance if they are able to feed on keratin, a proteinaceous constituent of these materials. There are approximately 30 species of moth larvae, 15 species of beetle larvae, and hundreds of species of bird-infesting biting lice (Mallophaga) known or suspected to be able to digest keratin, and they are the only animals that can digest it (Waterhouse, 1958). The pests of economic importance are found mainly in 2 groups: the carpet beetles and the clothes moths. Clothes moths are the more important of these groups in the southern states, but carpet beetles are more important in the remainder of the country. In either group, it is only the larvae that cause damage. They will feed on or damage many other substances of animal or vegetable origin besides fabrics and paper.

Although keratin-containing substances (wool, hair, and feathers) are their preferred food materials, carpet beetles and clothes moths will also attack other fabrics, such as cotton, linen, silk, and synthetics if the fabrics contain contaminants of nutritional value, such as urine, perspiration, beer, milk, or fruit juice. Merely handling a fabric with the bare hands will impart some nutritional factors to it, and even fungus spores settling from the air will add some nutrition (Pence, 1958). Clean, processed wool cannot support the normal life cycle of the clothes moth unless it is contaminated with certain nutritional supplements.

In one investigation, it appeared that minerals, proteins, and B vitamins were the attractant substances in fabric stains for the larvae of the webbing clothes moth, Tineola bisselliella, and the furniture carpet beetle, Anthrenus flavipes. Of the salts tested, K₂HPO₄, KCl, NaCl, and Na₂HPO₄ were the most readily eaten, and appeared to be the substances that would make a stain such as tomato juice attractive to these insects. However, the larva of the black carpet beetle, Attagenus megatoma, was not especially attracted to these salts or to the more common stains (Mallis et al., 1962).

There are many species of insects that are unable to digest keratin, but nevertheless can cause damage by chewing through keratin-containing fabric. Termites, crickets, cockroaches, silverfish, psocids, and even some dermestids may be included among such species.

Wherever they occur, the fabric-infesting insects are potentially highly destructive, but the substitution of synthetics for many of the woolen fabrics and the treatment of rugs, carpets, and other woolen fabrics with insectproofing agents in their places of manufacture have led to a steady decline of the over-all importance of this group of household pests. However, the hazard remains undiminished for unprotected furniture and fabrics imported from areas of the world where they are not treated. Even initially protected materials can lose their immunity to attack through cleaning and aging.

Beetle Species List

• Black Carpet Beetle, Attagenus megatoma (Olivier)
• Varied Carpet Beetle, Anthrenus verbasci (L.)
• Furniture Carpet Beetle, Anthrenus flavipes LeConte
• Common Carpet Beetle, Anthrenus scrophulariae (L.)
• Birdnest Carpet Beetle, Anthrenus pimpinella lepidus LeConte
• Odd Beetle, Thylodrias contractus Motschulsky

Four species of carpet beetles comprise not only the most important group of fabric pests, but also the group that is most difficult to control. The adults feed largely on pollen and nectar, and may enter homes in spring and early summer. All damage (figure 200) is done by the larvae, which develop in dark, undisturbed locations. Unlike clothes moth larvae, they spin no webbing, but their hairy cast skins and their sandlike pellets (shown in the figure; often the color of the fabric eaten) are evidences of infestation. The cast skins look much like live larvae, and may give the casual observer the impression that there is a greater infestation than is actually present. Pupation takes place in the last larval skin, and the adult may remain in the partially shed pupal skin for as long as 3 weeks. Evidence of a carpet beetle infestation may be the presence of the small, adult beetles flying to windows or larvae wandering from room to room. The adults resemble lady beetles in shape.

The source of a carpet beetle infestation is sometimes difficult to find. For example, one pest control operator treated an office building 3 times, each time failing to find the source of the beetles seen by the occupants. On the fourth attempt, he traced the beetles to a telephone cable in the wall, where the insects were discovered to be feeding on the insulation.

Whereas clothes moth larvae usually are found on their food material, carpet beetle larvae crawl about for considerable distances, and may be found on cotton goods or other materials on which they do not feed. They may often be found behind baseboards and moldings, in cracks in floors, behind radiators, in the air ducts of heater systems, and other secluded areas. If found in one area of a house, such as in the carpeting of a hallway, they can be expected to be found in adjoining rooms also. The adults and larvae of carpet beetles may also be seen outdoors in and under dead animals, in the hides and horns of cattle, or in the nests of birds, rodents, wasps, or bees (including the honeycomb). Beetles or clothes moths originating in such materials under floors or in wall voids or attics sometimes invade the living space, and the originally infested materials may continue to be sources of infestation after carpets and other infested articles have been treated (Linsley, 1944). The cast skins and fecal pellets of such insects in the attic sometimes drop into the rooms below via apertures around beams, through the holes in perforated ceiling tile, and around light fixtures. This material is sometimes mistaken for the frass of woodborers, and may lead to a mistaken diagnosis of the problem.

Except in the arid western states, the black carpet beetle is the most important species. In California, it is of little importance as a fabric pest. It is most likely to be found infesting stored food products, or when it is found on woolens, the infested items have usually arrived recently from the eastern United States. Among infested materials found in federal quarantine were "woolen rugs and clothing, silk clothing, carpeting, felts, furs, skins, yarn, upholstered furniture, wool-filled blankets, house insulations containing sheep wool and cattle hair or binders of farinaceous materials, meat and insect meal [rearing mixtures], kid leather, milk powders, casein, books, birds' nests, cayenne pepper, beans, peas, corn, wheat, rice, and a long list of seeds and seed products" (Back and Cotton, 1938). In a survey of 118 grain-storage and feed mills in Ohio, the black carpet beetle was found in 110 of the buildings (Triplehorn, 1965). Although not a serious grain pest, it was the most widely distributed insect observed.

Although the larvae can eat large holes through any suitable food material, they tend to eat the nap from the fabric and shun the base threads. In furs, they tend to cut hairs at the base with no injury to the hide, but they leave it bare in appearance. The larvae may also burrow through packaging material to obtain food, thus providing access for other species of insects (Truman and Butts, 1967).

Description. The adults (plate VI, 2; figure 201, A) are 2.8 to 5 mm long, shiny black and dark brown, with brownish legs. The full-grown larva is narrow, up to 8 mm in length, tapers toward the rear (carrotshaped), terminates in a tuft of long hairs, and has short, stiff hairs covering the body. It varies from light brown to almost black. The cuticle is hard, smooth, and shiny, resembling that of a wireworm. It is relatively resistant to pesticides.

Life Cycle. The number of days required by the various stages are: egg, 6 to 16; larva, 166 to 330; and pupa, 8 to 14. The period from egg to adult is 180 to 360 days, and the adult may live another 30 to 60 days (Laudani, 1961).

The female lays about 90 eggs in the lint under and behind baseboards, in cracks, in ducts of hotair furnaces, and other dark and protected places. There may be 5 to 11 larval instars, or even as many as 20 under particularly favorable conditions.

A Related Species

A black, indigenous dermestid, Attagenus alfierii Pic, resembling the black carpet beetle, has been reported from southern California in bird nests. It infests barley, cottonseed meal cake, and mixed feeds, and sometimes attacks fabrics in homes (Strong and Okumura, 1948).

This species infests the usual range of household articles attacked by carpet beetles, such as carpets, woolen goods, silks, skins, furs, feathers, hair, horn, cereals, red pepper, fishmeal, or any processed animal or plant food. However, the favored larval foods are dead insects and spiders, which may account for the frequent occurrence of the varied carpet beetle in insect collections in museums. In common with other carpet beetles, this species will feed on cottons, linens, and synthetic fibers if they are contaminated, but it will not feed on rayon acetate. In California, the varied carpet beetle is the most injurious fabric feeding dermestid, and its prevalence has been attributed to the wasp nests around homes, which these beetles also infest (Unsley, 1944).

Another Related Species

A newly introduced dermestid, Anthrenus coloratus Reitter, closely resembles the varied carpet beetle. It was originally known from Asia, Africa, and Europe, and has been found in Washington, D.C., Maryland, Illinois, and California. Its habits are apparently similar to those of other carpet beetles.

Description of Anthrenus verbasci. This species has a number of varieties. They differ in shape, size, color, and pattern of the scales, but in general the adults are 2 to 3 mm long, and have a varied pattern of white, brownish, and yellowish scales on the back and fine, long, grayish-yellow scales below (plate VI, 3; figure 201 B). Where ihe elytra terminate, they do not form a cleft as do those of the furniture carpet beetle, A. flavipes. The mature larva (plate VI, 2) is 4 to 5 mm long, and has a series of light- and dark-brown transverse stripes. If it is suddenly alarmed, the larva erects the 3 dense tufts of bristles and hair located on each side of the rear end of the body, spreading them out to form beautiful, round plumes (Back, 1938). The larva is broadest near the rear, and becomes narrower toward the front end, unlike other carpet beetles.

Life Cycle. The female lays about 40 eggs. There are usually 7 to 8 larval instars, but the number may vary from 5 to 16. The numbers of days for the various stages are as follows: egg, 17 to 18; larva, 222 to 323; and pupa, 10 to 30. The period from egg to adult is 249 to 354 days, and the adult may live another 14 to 44 days (Laudani, 1961).

As the name implies, furniture carpet beetles are best known for their attacks on upholstered furniture, feeding on hair padding, feathers, and woolen upholstery; but they also attack the usual food materials that are eaten by other species, including the glue of bookbindings and natural fiber brushes. This species is distributed throughout the United States, and is important in California, where it thrives in a slightly drier environment than the varied carpet beetle.

Description. The adults (plate VI, 1; figure 201, C) are 2 to 3.5 mm long, spotted yellow, white, and black above and white beneath. They are slightly larger and more rounded than the varied carpet beetle, and have a cleft where the elytra meet posteriorly. The adult spends a quiescent period within the old larval skin before becoming active. Recently hatched larvae are white, but turn light yellow to dark red or chestnut brown as they develop. They are about 5 mm long when full grown. They are widest in front and become narrower toward the rear. Mature larvae are darker than those of the varied carpet beetle, and are able to run swiftly.

Life Cycle. The female lays about 60 eggs in from 1 to 3 clutches, generally in such places as the pile of mohair chairs, in the nap or on the surface of clothes, and in cracks and crevices. The numbers of days for the various stages are as follows: egg, 9 to 16; larva, 70 to 94; and pupa, 14 to 17. The period from egg to adult is 93 to 126 days, and the adult may live another 30 to 60 days (Laudani, 1961).

This species occurs throughout much of the world, but in the United States it is most abundant in the northern area. It is of little importance in California. One unusual feeding habit of this carpet beetle is its tendency to eat slits in carpets that correspond in position with the floor cracks (Back, 1938).

Description. The adult is 3 mm long, gray to black, with a varied pattern of whitish and orange scales on the back, and with whitish and orange-red scales around the eyes and on the clypeus. The mature larvae are about 3 mm long, reddish brown, and have many black or, brown hairs. They move about actively.

Life Cycle. The female lays about 60 eggs on textiles or other larval food sources. The number of days for various stages are: egg, 10 to 18; larva, 60 to 80; pupa, 7 to 12. The period from egg to adult is 77 to 110 days, and the adult may live another 20 to 30 days (Laudani, 1961).

This species is of interest as a fabric,pest mainly in California, where several races or varieties are indigenous. The adults are mottled brown and white, and the black larvae are similar to those of the black and furniture carpet beetles. In California, this species is common in the nests of the house sparrow, house finch, black phoebe, barn swallow, and cliff swallow (Linsley, 1944). The adults emerge outdoors in March and April and fly to flowers for feeding and mating, then usually seek out bird nests for oviposition but may find their way into houses. The larvae feed primarily on feathers and animal hairs. They pupate in late fall, and the adults overwinter in the last larval skin.

The odd beetle, also called "tissuepaper beetle," is related to the carpet beetles despite their mutual lack of resemblance in general appearance. It is widely distributed in the United States, but not in large numbers, and is seldom a pest. A striking feature of the species is the great difference in appearance between male and female. The male is 2 to 3 mm long, slender, yellowish brown, with disproportionately long legs and antennae. When at rest, the elytra are contiguous for only about one-third of their length, and then separate to reveal the abdomen. The wingless, larviform females (plate V, 8) are also brownish in color, but differ from the males so strikingly that they would hardly be suspected to be of the same species. Both sexes have a median ocellus between the compound eyes.

The larvae somewhat resemble those of the common carpet beetle, but lack the tuft of hair at the rear end and the long hairs on the dorsal surface. Instead, there is a transverse row of stout bristles at the rear edge of each body segment, those on the prothorax being clubshaped. The larva can roll itself up into a ball when disturbed. The larvae feed on dry animal matter and woolen, silk, or muslin cloth, even when it is unsoiled. They can penetrate tissue paper used to wrap their normal food materials, but the common name "tissuepaper beetle" does not appear to be appropriate.

Moth Species List

• Webbing Clothes Moth, Tineola bisselliela (Hummel)
• Casemaking Clothes Moth, Tinea pellionella (L.)
• Carpet Moth, Trichophaga tapetzetta (L.)
• Fan Palm Catepillar, Litoprosopus coachellae Hill (Noctuidae)

Clothes moths are small, yellowish or golden insects, with narrow wings fringed with long hairs. They are not attracted to light, and attempt to hide when disturbed, so the housewife is not likely to see them. However, they are occasionally seen flying in subdued light. Most moths suspected by the layman to be clothes moths are other species, usually harmless accidental intruders. Clothes moths are most likely to become evident from damaged fabrics and by the presence of silken webs spun by the larvae. The larvae can feed on clothing, carpets, rugs, furs, fabrics, blankets, stored wool products, upholstery, piano felts, and brush bristles. They may feed on fabrics of vegetable origin or synthetics, if the fabrics are mixed with wool, or may use such materials to construct their cocoons.

This cosmopolitan species is the most common clothes moth in the United States. It is very destructive. Damage to clothing occurs most commonly in dark, hidden areas, as under collars and cuffs, but sometimes the larvae are very active and may be seen crawling on clothes or on the floor beneath badly infested furniture. When feeding between the carpet and the floor, the larvae may extend their silken feeding tubes along the floor cracks, and the feeding pattern is indicated by the webbing beneath the carpet (Curran, 1949).

Besides feeling on clothes, carpets, rugs, and upholstered furniture, the webbing clothes moth feeds on furs, stored wool, and such miscellaneous articles as the animal bristles of brushes and the felts in pianos. In nature, it feeds on pollen, hair, feathers, wool, fur, dead insects, and dried animal remains.

Description. The body and wings of the adult are uniformly golden colored, except for reddish golden hairs on the top of the head (plate VI, 4; figure 202). The wingspread of the female is about 11 mm and that of the male is somewhat less.

Life Cycle and Habits. The adults are very active, can penetrate through surprisingly narrow cracks, and can fly considerable distances (Griswold, 1944). However, they are not attracted to light, and gravid females are weak fliers. The female dies after attaching about 40 to 50 eggs, singly or in groups of 2 or more, to the threads of infested clothes over a period of 2 to 3 weeks. The eggs (figure 202, inset) hatch within an average of 4 to 10 days in summer, but take as long as 3 weeks in winter.

The newly hatched larvae are only about 1 mm long, and translucent white. Some larvae may spin a small, frail, silken tube or tunnel, incorporating into the silk some fibers, excrement, or cast skins. They then feed within the confines of the tube. Others may merely spin flat mats under which they crawl about, or remain naked for several days before they spin any webbing. Some larvae leave the webbing and crawl about unprotected. The feeding tubes and silken mats make up the webbing that characterizes an infestation. The number of larval molts can vary from 5 to 45, and the period required for larval development can vary from 35 days to 2.5 years, depending on the availability of food as well as relative humidity and temperature. The full-grown larva is shiny, creamy white, and about 12 mm long. When preparing to pupate, it spins a pupal case of silk about 8 mm long, again incorporating textile fibers and excrement. The period required for pupation varies with temperature, but can be as brief of 8 or 10 days in summer or as long as 3 or 4 weeks in winter. The length of the life cycle varies from 50 to 90 days, but can be extended to as long as 4 years under unfavorable conditions (Back, 1923).

In the United States, the casemaking clothes moth is much less important than the webbing clothes moth as a pest. It can be found throughout the country, but is most common in the southern states. It is particularly capable of damaging hair and feathers, but will also feed on spices, tobacco, hemp, and skins. The moth derives its common name from the small silken case (figure 203) that the larva spins about its body and carries about wherever it feeds, thrusting its head and legs out in front. Sometimes in a severe infestation, larvae may crawl up on a wall in large numbers, dragging their cases behind them.

Description. The adult is somewhat smaller and more brownish than the webbing clothes moth, and has 3 dark spots on the wings, but the spots become less discernible if the wing scales are worn off. The hindwings are yellowish brown. The males are smaller and lighter in color than the females, and are active fliers. The females are sluggish, and fly only for short distances. The first thoracic segment of the larva, at first brown, later becomes black, and is divided by a longitudinal band.

Biology. The larva can turn within its case and feed on food material at either end without altering tlie position of the case. If the case is removed from the larva when it is very near pupation, the larva will die. Rarely will the larva spin a web directly on the material on which it is feeding, but will usually attach its case to the material by means of silken threads. Pupation takes place within the case after both ends have been sealed with silk. There were found to.be 3 or 4 generations a year at 26 ° + 8 °C (79 °F) and 82% +10% relative humidity when larvae were fed on woolen fabrics impregnated with 5% yeast (Cheema, 1956).

This moth is rare in the United States. It is larger than the webbing or casemaking clothes moths, having a wingspread of about 19 mm. Its head and the basal third of the forewings are black, the outer two-thirds of the forewings are creamy white, and the hindwings are uniformly pale gray. The larvae prefer coarser and heavier fabrics than those of the 2 species just described, and they construct burrows or silk-lined galleries in all directions throughout the infested materials, such as carpets, tapestries, feltings, furs, and skins. This species has also been reported to be destructive to wallpaper (Back, 1923).

The best way to combat carpet beetles and clothes moths is to prevent them from becoming established in the home. The principal weapon is the vacuum cleaner and its brush attachment. Rooms should be cleaned often enough to prevent the accumulation of lint, hair, and other carpet beetle and clothes moth food materials. Close attention should be given to rugs and carpets, draperies, upholstered furniture, closets (especially those containing woolens and furs), radiators and heaters, corners, cracks, baseboards, moldings, and other hard-to-reach places. If an infestation is known or suspected, the sweepings of the vacuum cleaner should be disposed of immediately in such a way as to destroy the insects, to prevent a transfer of infestation from one part of the house to another (Pence and Davis, 1969).

Abandoned nests of birds, rodents, and insects. (particularly bees and wasps) that are in or near the house should be removed, for the larvae of both carpet beetles and moths may feed on insect remains that they may contain. Bedding places of pets should be kept clean. Mounted animal specimens or trophies (or even fur-covered toys), insect collections, stored woolens, carpeting, clothing, feathers, furs, old spices, cereals, or seeds should be examined for signs of infestation. The attic and garage should be included in the inspection. Avoid bringing carpet beetle adults into the house on cut flowers, where they are sometimes found feeding on pollen.

Dry-cleaning kills all stages of clothes moths and carpet beetles, but gives no protection against reinfestation. Many cleaning establishments and pest control firms can apply protective treatments. Woolen garments or materials that have been stored for a long time should be occasionally shaken and aired. Brushing can crush most eggs, particularly the fragile eggs of carpet beetles. If they cannot find protection from light, many larvae that are not removed by the brushing will fall from any garments hung in the sun, as on a clothesline. (It is unwise to use such treatment for furs, since they are subject to fading, drying, or even theft.)

Woolen clothing and blankets can be protected against feeding damage by carpet beetles and clothes moths by spraying them lightly with oil solutions of methoxychlor or allethrin (Bry et al., 1968); Gardona® (Bry et al., 1969); Strobane® or Perthane® (USDA, 1966); or other recommended pesticides. A household hand sprayer may be used, or a pesticide may be purchased in a ready-to-use pressurized container that delivers a coarse spray. The clothing or blankets should be hung on a line and sprayed lightly and uniformly until their surfaces are moist (USDA, 1966). Infants' apparel and blankets should be cleaned or washed, and sprayed only if they are to be stored. They should be laundered and dry-cleaned before further use.

Woolens stored in a container, trunk, or closet may be fumigated with paradichlorobenzene (PDB) crystals and naphthalene flakes or balls (mothballs). The storage container should be tightly sealed. Loose-fitting containers can be lined with heavy paper and sealed with tape. One lb (0.45 kg) of either fumigant is enough to treat 20 cu ft (0.57 cu m) of storage space. Scatter the fumigant between the layers of paper separating the articles to be treated. In a reasonably tight container, 1 application a year should suffice. In closets, apply the fumigant to the floor and shelving, and replenish the supply after it evaporates. All plastic buttons should be removed from clothing before treating, and plastic hanger's should not be used, for PDB and mothballs are destructive to plastics and may fuse them with the fabrics.

The 20% Vapona Resin Strip (polyvinyl chloride resin impregnated with dichlorvos) is worthy of trial in almost any situation in which the pests are in a confined area. The strip slowly gives off vapors of dichlorvos, which is much more toxic to insects than PDB or naphthalene, less toxic to man when used as directed in limited storage areas, and is also less expensive. Either the 6-in. (15-cm) strip or the 2-in. (5-cm) "ministrip" can be subdivided to the appropriate size for the space to be fumigated. In a small, tightly scaled container, such as the Schmidt box in which pinned insects are kept, vapors leave a piece of Vapona Resin Strip very slowly because of vapor pressure built up in the box. As little as 1 sq in. (6.45 cm2) of resin strip is 32 times the required amount to protect a Schmidt box of 150 cu in. (2,458 cm3) from museum pests (Ryckman, 1969).

Woolens wrapped in heavy paper or enclosed in a cardboard box with sealed edges are protected against fabric pests, provided the woolens are not already infested. Spraying of furs is not recommended, for they can be protected with PDB, mothballs, or dichlorvos resin strips as recommended for woolens, or they can be frequently shaken and aired. If living or dead insects, fecal pellets, cast skins, or fiber particles are not present, as they would not be after the fur is brushed, shaken, or cleaned, mandibular scars on the individual fibers are unmistakable clues to insect damage. An illustrated guide for the diagnosis of fur damage with the aid of a microscope is available (Pence, 1966).

The edges of rugs or carpets can be pulled up and the common household sprays can usually be applied on both sides, as well as on both sides of the pad. Treatment is particularly important under heavy furniture that is seldom moved. Upholstery and draperies can be sprayed, following the same directions discussed for clothing and blankets.

Pesticide sprays may be applied to any surfaces upon which fabric-infesting insects are likely to crawl, such as along the edges of wall-to-wall carpeting, in closets, behind radiators, and in corners, cracks, baseboards, moldings, and other hard-to-clean places. Closets, particularly, should be thoroughly sprayed after removing the contents. Chlordane 2%, premium grade malathion or ronnel 5%, and lindane or diazinon 0.5% have been recommended as insecticides (USDA, 1966). Insecticide dusts are useful to blow into attics, basements, wall voids, or other areas difficult to reach with a spray, or dusts may be sprinkled on the floor and swept into cracks, after which the rug can be put back into place.

Deodorized kerosene (base oil) with dissolved insecticides, when applied as a mist or fog, remains as an oily deposit on the surface of a carpet. The addition of 30 to 50% of isopropyl alcohol (rubbing alcohol) results in good penetration of the insecticide to the bases of the fibers, where fabric pests feed (Pence and Viray, 1963). Oils can cause the nap to separate from the backing, and then the carpet buckles. By improving penetration, the isopropyl alcohol reduces the amount of oil required and decreases the possibility of damage to the carpet. Only enough spray should be used to reach the bases of the fibers, and any excess should be avoided. A kerosene-isopropyl alcohol solution should be used only for treatment of carpets and rugs - not as a space spray. Windows and doors should be left open during application. Pilot lights should be extinguished before treating near floor or wall furnaces, hotwater heaters, or other natural gas appliances.

Water-base sprays can be effectively used if a wetting agent is added. Such sprays should not contact nonwashable wallpaper or other materials that will color-run or stain.

Fumigation is an effective method for the control of fabric pests. If the pests are widespread in a house, the entire building can be fumigated by a pest control operator. Fumigation is expensive, and requires that the house be vacated for a day or two. It provides no residual protection against reinfestation. Some pest control operators and storage firms have fumigation vaults where infested pillows, mattresses, upholstered furniture, and similar small articles can be fumigated when the infestation is localized. Methyl bromide, the most commonly used gas for fumigating buildings, is known to be a good ovicide. It was found to be effective against all stages of carpet beetles (Pence and Morganroth, 1962).

Insectproofing Agents

In the United States, the 2 most commonly used insectproofing agents have been DDT and dieldrin. [The term "insectproofing" is used here, even though the term "mothproofing" is firmly established in the literature. There appears to be no reason to believe that moths are more important than carpet beetles as destroyers of fabrics, and the beetles are much more difficult to control.] Since the recommendation by the Life Sciences Panel of the President's Science Advisory Committee in 1963 that more specific mothproofing treatments be developed, entomologists and chemists of the Savannah Laboratory of the USDA Stored-Product Insects Research Branch have searched for substitutes for the organochlorine compounds. They found that Ciba-Geigy C-9491 or iodofenphos [O-(2,5-dichloro-4-iodophenyl) O,O-dimethyl phosphorothioate], when applied to woolen cloth from emulsion bath treatments, protected wool fabric from feeding damage by larvae of the black carpet beetle, Attagenus megatoma, and the webbing clothes moth, Tineola bisselliella, at deposits as low as 0.05 and 0.03% by weight of the cloth, respectively (Bry et al., 1971, 1972). The oral LD₅₀ of this compound to rats is reported to be 2,000 mg/kg, approximately 8-fold greater than the LD₅₀ for DDT and 40-fold greater than that for dieldrin. However, the registration of dieldrin is still valid for "mothproofing by those manufacturing processes which utilize the pesticide in a closed system" (EPA Determination and Order of June 25, 1972).

According to a more recent report from the same laboratory, when resmethrin was applied to woolen cloth as an aerosol, it protected the cloth against feeding by black carpet beetles and webbing clothes moths for as long as 6 months (Bry et al., 1973a). These 2 species were also killed when hit by the resmethrin aerosol. This versatile and relatively safe synthetic pyrethroid shows promise as a replacement for some insecticides now used in the home against carpet beetles and clothes moths (Bry et al., 1973b).

This insect is an occasional pest in southern California and Arizona. The adult is a light-tan moth, with dark lines on the forewings (figure 204). The full-grown larva is approximately the size of a mature cutworm larva - about 40 mm long and when mature usually has a pinkish or pinkish-brown color. The larvae normally feed on the flowers, flower shoots, and to some extent on the fruits of fan palms. Large numbers of the more mature larvae sometimes crawl to the ground, or may be blown down by strong winds, and then sometimes enter homes, where they may make their cocoons from material obtained from rags, drapes, or other household fabrics. Large patches of pile from rugs, drapes, or even velvet can be removed by the larvae. They are attracted to light, and therefore any areas of ingress into lighted homes near palm trees should be closed at night. The application of DDT spray (no longer available) to the crowns of palm trees in June or July and the application of lead arsenate to the flowering shoots early in the season were found to be effective controls (Flock, 1951). Tests have not been made with currently available insecticides.

Silverfish Species List

• Silverfish, Lepisma saccharina L.
• Firebrat, Thermobia domestica (Packard)
• Fourlined silverfish, Ctenolepisma lineata (F.)
• Gray Silverfish, Ctenolepisma longicauda Escherich

Silverfish are primitively wingless insects, without metamorphosis (ametabolous), and have flattened, slender, scale-covered bodies that are sometimes silvery, usually with a metallic sheen. The body tapers gradually to the rear, giving the insect a fishlike appearance, suggesting the common names "silverfish" or "fishmoths" or the German Fischen. They have long, slender antennae and 3 long, slender appendages at the rear of the body, suggesting another common name - "bristletails." Silverfish are very long-lived insects, and are unique in continuing to molt their skins for years after they become adults. The female usually lays fewer than 100 eggs, singly or in small groups, but ranging up to as high as groups of 45 for firebrats, in cracks and crevices, or behind baseboards. The eggs are elliptical, and are only about 1 mm long. They hatch in from 2 weeks to 2 months or more, depending on conditions. The young closely resemble the adults, except for size. In their third or fourth molt, the young develop the scales that thereafter give the insects their characteristic coloring.

Silverfish are nocturnal insects that may occur almost anywhere in a house, including attics, wall voids, and subfloor areas. They are very fastmoving, and sometimes are seen only when they are trapped in such places as washbasins and bathtubs, where they remain because they cannot climb smooth, vertical surfaces.

Silverfish feed on any human food, and in addition they may feed on starch, paste, glue (as in bookbindings), starched cotton, linen, silk. or certain synthetic fibers and paper products (figure 205), to which they are attracted by sizing or, as in the case of wallpaper, by paste. Sometimes they cause wallpaper to flake off by removing the paste. Possibly, the most common evidence of the presence of silverfish is paper with the glaze removed in an irregular fashion, with irregular holes, or with the edges notched. Scales, excrement, or yellowish stains may be seen on paper or fabric that has been infested. Silverfish may also feed on dead animals, including dead or injured individuals or cast skins of their own species.

As might be expected, silverfish are serious pests in libraries, where they attack bookbindings and heavily sized paper. They seldom injure wool, hair, or other fibers that are of animal origin. Like termites, they are said to harbor organisms that aid them in the digestion of cellulose materials. A silverfish infestation develops slowly, so when these cryptobiotic insects become numerous enough to be seen occasionally in a home, this indicates that the infestation is probably an old one, or that large numbers were brought into the home as eggs, active stages, or both, in cardboard cartons, books and papers, and other household materials. All the species described in this chapter are in the family Lepismatidae.

This common household pest is believed to have come originally from the tropics but, like so many other household pests, it has been able to extend its range to temperate countries by dwelling in damp and warm locations in the homes and other buildings of man. Silverfish or their eggs can be unknowingly transported from one building to another in cardboard cartons, books, papers, and many other carbohydrate substances.

Description. This is a silvery-gray insect with a metallic sheen (plate V, 5; figure 206). It attains a length of about 12 mm, not including the appendages.

Life Cycle. According to Sweetman (1939), females might lay 1 to 3 eggs per day on a number of successive days or at intervals of several days or even weeks. Wigglesworth (1964) stated that the female alternately molted and laid eggs, and might molt up to 50 times before becoming an adult. He found that the eggs hatched in 50% relative humidity at 22 and 27 °C (71 and 80 °F), but only above 75% RH at 29 and 32 °C (84 and 90 °F). He noted that the period from egg to adult could be as long as 2 or 3 years or, under favorable conditions, only 3 or 4 months. Development was favored by warmth and high humidity. Sweetman also observed that at temperatures ranging from 22 to 32 °C (71 to 90 °F), nearly all reproduction occurred at above 75% RH, and the highest percentage of oviposition took place at 84 to 100% RH. This insect may continue to grow for well over 3 years, molting every 2 or 3 weeks.

As the common name implies, firebrats are found in locations where temperatures are high, such as around ovens, heating units, fireplaces, and hot-water pipes, provided these places are not too dry, for they thrive best where it is both warm and damp. They can be serious pests in bakeries. They are cosmopolitan in distribution, but prefer temperatures above 90 °F (32 °C), with an optimum of 98 to 102 °F (37 to 39 °C), but nymphs and adults can survive at temperatures between 32 and 112 °F (zero and 44 °C). Eggs fail to hatch below about 70 °F (20 to 22 °C) (Sweetman, 1938).

Description. This insect is only slightly larger than the silverfish, being about 14 mm long, silvery, but with transverse gray areas that give it a mottled appearance (plate V, 6). When its scales are rubbed off, the light-yellow color of the body can be seen.

Life Cycle. At temperatures of 90 to 106 °F (32 to 41 °C), the female may oviposit when she is 45 to 135 days old, depositing her eggs in crevices, an average of about 50 in a lifetime. Like the silverfish, the firebrat continues to molt during its adult life. Only 1 clutch of eggs is laid between molts, and fertilization must take place before each clutch of eggs is laid. The elliptical, nearly white eggs are about 1 mm long and 0.7 mm wide in their greatest dimensions. Optimum conditions for incubation of eggs are 99 °F (37 °C) and 76 to 85% relative humidity, and eggs kept at these conditions will hatch in 14 to 18 days. Under optimum conditions, only 1 day or less is spent in the first instar, 4 in the second, about 6 in the third and fourth, and about 8 in the fifth to tenth. This period gradually increases to 12 or 13 days in further instars, and the insect may pass through 45 to 60 instars before death (Sweetman, 1938). Brett (1962) found that females started to oviposit in the fourteenth instar, and that molting of the growing firebrats appeared to be continuous, with very little change in size occurring after the thirty-fifth instar.

A curious and noteworthy thing about firebrats is their "love dance," described by Brett as follows:

The courtship of firebrats has been described as a "love dance" wherein the male constantly approaches the female. and repeatedly contacts her antennae, mouthparts, and legs. As the male whirls about, he curves his abdomen and deposits a sperm bundle about one-half inch in front of the female. He then contacts her head and legs and comes to rest, apparently losing all interest in her. After his final contact, the female moves forward, straddles the sperm bundle, and secures it to certain reproductive structures.

At 37 °C (99 °F) and 50 to 70% relative humidity, firebrats have been reared both with and without liquid water to imbibe, but in one experiment the insects reared with water weighed 50% more than those receiving none. Firebrats can obtain water from wet cotton wicks, but they avoid actual drops of water on the wick. Without access to water, development is slower, and oviposition is retarded and decreased (Adams, 1933). At ordinary room temperatures, firebrats lose water from their bodies only below 45% RH; above that, they absorb water via their cuticles (Noble Nesbitt, 1969).

Lepisma saccharina and Thermobia domestica are seldom seen outdoors in temperate regions, but have been occasionally found under bark, in bird, mammal, and insect nests, and in debris (Linsley, 1944).

This species occurs in the eastern United States as far south as Georgia and Arkansas and also in California. This and the following species are not so limited in distribution in a building by temperature and moisture conditions as the silverfish already mentioned and the firebrat. Consequently, C. lineata can be found throughout the house and in the basement, in wall voids, and in the attic, where it is often seen in large numbers, particularly in houses with roofs of wooden shingles. It occurs in the mulch of flower beds around the foundation, and also in the garage, even if it is not attached to the house (Zeigler, 1955).

Description. The fourlined silverfish is about 15 mm long, tannish gray, and has 4 dark lines extending down the length of its back. The young are light brown, and are often tinged with pink until the fourth molt, which occurs a month or so after hatching. The subspecies Ctenolepisma lineata pilifera (Lucas) frequently enters homes in rural areas of northern California (Smith, 1970).

This species is similar in size and habits to C. lineata, but differs somewhat in color, being uniformly light to dark gray (plate V, 7; figure 206). It has been reported from a few eastern and southern states and from California and Hawaii. In laboratory tests, it was found to do much more damage to paper and fabrics than Lepisma saccharina or Thermobia domestica (Sweetman and Kulash, 1944). Mallis (1941b) found C. longicaudata to be an important pest in southern California, being distributed throughout the home from basement to attic in both old and new houses, but never outdoors. He observed that ventilators and heat conduits originating in the basement facilitated the spread of this insect throughout the building.

Dietary Factors. This species is the most widely distributed and abundant silverfish in Australia, where its biology was intensively investigated by Lindsay (1940). In wallpaper, the palatable materials were the starch and dextrin sizes on the surface. In writing paper, the palatable material was the "chemical pulp" containing degraded celluloses. Papers containing more than 45%, "mechanical pulp" were not eaten; the unpalatable materials were associated with the "ether extract" fraction. Cellulose-digesting bacteria, and enzymes that passed forward from the midintestine, supplemented the action of the gizzard in the digestive process.

Residual liquid sprays have long been used for control, including 2% chlordane, 0.5% diazinon, 0.5% lindane, and 0.5% propoxur. Lindane possibly has special merit because of its vapors, which may penetrate into cracks and crevices not reached by the spray. Dichlorvos added to any spray should provide a similar action. Chlordane 5% dust and the silica aerogel Dri-die 67® have been used effectively. A widely distributed infestation should be treated with the same thoroughness and in very much the same out-of-sight places as suggested for the control of German or brownbanded cockroaches in chapter 6.

In recent years, pest control operators have had increasingly erratic results with chlordane against the firebrat. In laboratory tests, residues of chlordane gave less than 100% mortality on a porous surface (unfinished plywood) in 144 hours when used at less than 4% concentration, whereas diazinon, dichlorvos, malathion, and propoxur gave 100% kills in 24 hours used at 0.25, 0.25, 1.25, and 0.55% concentration, respectively. By far the most effective insecticide tested in both topical and residual treatments was chlorpyrifos (Dursban®). This insecticide gave a 100% kill on unfinished plywood in 12 hours at 0.20%, concentration (Luke and Snetsinger, 1972).

In the author's experience, when treating mixed populations of cockroaches and silverfish, a thorough cockroach control has invariably eliminated silverfish also. However, Lepisma saccharina and particularly Thermobia domestica may occur in very localized infestations, and treatment can be confined to the areas where they are known to occur. For firebrats, emphasis is placed on treatment of areas of high temperatures, such as around heating units, heating pipes or conduits, steam or water pipes, and fireplaces (Zeigler, 1955). Ctenolepisma lineata is more difficult to control because it is so widespread both inside and outside the house.

The fourlined silverfish particularly, and sometimes other species, may be found in attics. Dri-die is so light that it can be uniformly blown throughout the attic from a single crawl hole. Because it is inorganic, it affords protection against silverfish and other attic-infesting pests for much longer periods than the conventional organic pesticides.

Most of the various insecticide dusts can be used effectively to eliminate existing infestations. For attic dusting, electric blowers (figure 32, chapter 3) or water-type fire extinguishers (figure 33, chapter 3) can be used, and the latter, because of the narrow discharge orifice, can also be used for blowing dust into wall voids or under cabinets through existing apertures or through holes that may be drilled in appropriate places.

Among fabrics, silverfish do most damage to rayon. Zeigler (1955) noted in several cases of damage to rayon draperies that most of the holes made by the fourlined silverfish were made at windowsill level. He noticed that the insects were often found between the drapery and its lining. A light mist of residual pesticidal spray can be applied to cornices and both sides of the infested draperies.

Poison Baits. Adams (1933) found that the odor of ground rolled oats, which was generally considered to be a favored food of firebrats, did not attract them at a distance of 8 cm, even after the insects had been denied food for 2 days. Direct antennal contacts were required for strong, positive responses to dry food particles. This probably accounts for the very poor results the author has had in attracting firebrats to currently popular poison baits when the baits were placed in traps on the centers of the floors of enclosed wooden boxes 29 cm long, 14 cm wide, and 9 cm deep, even when other food sources were absent. A few insects would invariably live longer than 25 days without being attracted to the bait. Many firebrats congregated on the vertical walls of the boxes, and were seldom seen crawling over the floors. Contacts with baits were probably by chance. This was in accord with the observation of Berger (1945) that the location of a baited trap, and not the bait, determined the number of firebrats caught. The same is probably also true of other silverfish species. When placing poison baits in areas where silverfish normally crawled, Berger found that among equally available foods, the firebrats showed preferences. He concluded that because of the ease of mixing and their availability, wheat flour 85% and powdered sugar 15% were about the most practical food combination for bait. However, another factor to be considered is the repellency of the insecticide in the bait. For example, Mallis (1941b) found that Ctenolepisma longicaudata was repelled by white arsenic, sodium arsenate, sodium fluosilicate, and sodium fluoride in flour pastes, but not by barium fluosilicate or barium carbonate.

Traps. Where the application of insecticides is undesirable, silverfish can be trapped. The outer surface of a small jar, such as a 1-oz ointment jar, can be covered with masking tape to enable silverfish to climb up the outside of it. The insects fall into the jar, and cannot escape because they are unable to climb its smooth, vertical walls. The traps should be placed in paths normally used by silverfish, as in the intersections and corners of a pantry or bookcase or next to the baseboard on the floor (in the warmest locations, in the case of firebrats). The first to advocate a trapping procedure for firebrats was Mallis (1941b), who placed a teaspoonful of white wheat flour in the jar. In our replicated laboratory experiments with large numbers of firebrats, we found that the trap jars had to be judiciously placed, as in corners of the experimental boxes, but that the kind of bait used had no influence on the number trapped. Empty jars trapped as many firebrats as jars with wheat flour and sugar or wheat flour, sugar, and chipped beef.

Mallis et al. (1958) made a comparison of the amount of, feeding done by the larvae of the webbing clothes moth (Tineola bisselliella), the black carpet beetle (Attagenus megatoma), the furniture carpet beetle (Anthrenus flavipes), and the adults of the firebrat (Thermobia domestica) to 3 classes of fabrics: (1) synthetic (nylon, dynel, dacron, orlon, vicara, and acetate rayon); (2) natural (silk crepe, wool [AATQ, linen, and cotton percale); and (3) a combination of wool and synthetic fabrics (86% wool and 14% nylon, 45% wool and 55% orlon, and 45% wool and 55% viscose rayon). The clothes moth and the carpet beetle did extensive damage to wool and the combination of wool and synthetic fabrics. The furniture carpet beetle fed extensively on acetate rayon fabric, but the black carpet beetle did not. The firebrat was the only species that fed extensively on viscose rayon. It also fed slightly on silk crepe and linen. It is evident from the feces of silverfish that they digest silk, whereas if carpet beetles feed on silk, an examination of the feces shows that the material remains undigested (Hartnack, 1943).

Mallis et al. (1958) observed that the carpet beetles fed slightly on nylon, but the clothes moth and the firebrat did not. None of the 4 species they tested did any damage to dynel, dacron, orlon, vicara, or cotton percale. However, any fabric was attacked when contaminated with nutrient material, such as starch, beer, urine, fats, and molds. Stains containing minerals, proteins, and B vitamins caused fabrics to be more attractive, even those that would otherwise not be infested. The predilection of firebrats for viscose rayon noted by Mallis et al. had also been demonstrated by Wall (1953) for both the firebrat and another species of silverfish, Ctenolepisma lineata.

Many species of insects have been implicated in damage to fabric. In some cases, stains or contaminants of some nutritional value have initiated the attack. This appeared to be the explanation for some damage to a nylon viscose rug by southern fire ants, Solenopsis xyloni McCook, that was similar to damage caused by carpet beetles (Smith, 1965). Finley et al. (1968) exposed a number of cotton and synthetic fabrics to the American cockroach (Periplaneta americana), the house cricket (Acheta domesticus), and the striped earwig (Labidura riparia). Half of the 144 pieces of fabric were stained by dipping them into hot animal fat. The amount of visible damage from cockroaches to stained and unstained cotton fabrics (unfinished and resin-finished fabrics) and to unstained synthetic fabrics was negligible, but damage to stained acetate, viscose, and triacetate was extensive. Crickets preferred the same 3 synthetic fabrics as the cockroaches, and damaged both stained and unstained fabrics. Stained and unstained polyester, nylon, and acrylic fabrics were attacked to a lesser extent, and cotton was undamaged. Earwigs caused a slight "picked appearance" on the stained nylon.

Most of the termites that normally feed on wood eat fabrics of cotton, linen, jute, silk, rayon, and leather. Termites coming up through the floorboards and joists can damage carpets (Harris, 1961). Termites may destroy materials they do not use as food but which are damaged when the insects bore through them or pack earth against them. The termite Cryptotermes brevis readily attacks cellulose fabrics (Light, 1934a, b). Termites, crickets, and silverfish will attack cotton, especially if it is starched or soiled (Labarthe, 1964). Sometimes, the injurious insect destroys the fabric to gain access to fibers in building a nest or cocoon, e.g., damage from the fan palm caterpillar, Litoprosopus coachellae, as already described (figure 204).

There are many cases of damage to fabrics merely because they are in the way of insects. An example would be carpeting damaged by termites and the adults of woodwasps and certain woodboring beetles, when it happens to be in the way of insects emerging from the wood floor. The insect must bore through the fabric in order to escape. A rare and curious type of damage was reported from a home in which insect damage to a man's suits had amounted to about $1,000. Drugstore beetles (Stegobium paniceum) (figure 193, chapter 7) infesting cayenne pepper in the kitchen pantry had apparently found their way to a clothes closet, via the wall voids, and emerged in the closet to gather on a shelf. They dropped from the shelf onto the right shoulder of each suit, cut their way through the fabric, and dropped to the floor. Removal of the infested spices and spraying of the closet prevented further damage (Cushing, 1970).

Figure Captions

Fig. 200. Furniture carpet beetle, Anthrenus flavipes. Top, damage to a woolen carpet; bottom, fecal pellets, greatly magnified.
Fig. 201. Adults and larvae of the principal species of carpet beetles. A, black carpet beetle, Attagenus megatoma, B, varied carpet beede, Anthrenus varbasci; C, furniture carpet beetle, Anthrenus flavipes.
Fig. 202. Webbing clothes moth, Tineola bissellielia, adult and larvae. Inset, eggs.
Fig. 203. Silken cases of the casemaking clothes moth, Tinea pellionella
Fig. 204. Fan palm caterpillar, Litoprosopus coachellae. Left, larva and palm flowers on which it sometimes feeds; right, adult female.
Fig. 205. Paper damaged by silverfish.
Fig. 206. Two common thysanurans. Left, silverfish, Lepisma saccharina; right, gray silverfish, Ctenolepisma longicaudata.

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Last updated on Aug 23, 2002 by leowest@ucrac1.ucr.edu