Part 1

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U. S. DEPARTMENT OF AGRICULTURE

FARMERS' BULLETIN No. 1346

CARPET BEETLES AND THEIR CONTROL

CARPET BEETLES, or so-called "buffalo moths," are common household pests usually associated in their destructive work with clothes moths. Ordinarily they are not so destructive as clothes moths, because they reproduce only once a year, and then not so abundantly.

Experienced housewives throughout the North are familiar with the stout, oval, reddish-brown, hairy grubs or larvæ of the common carpet beetle, found beneath carpets or in clothing. In southern homes, however, the longer, slender, golden-brown larva of the black carpet beetle, with its tuft of golden bristles, is more common.

All carpet-beetle larvæ feed upon fabrics or upon various articles, including upholstered furniture, containing wool, silk, hair, fur, bristles, or feathers. They even feed upon dried animal matter.

Protection against carpet beetles can be secured in tight chests and trunks by the use of the crystals of naphthalene, paradichlorobenzene, or camphor, or by the fumigants carbon disulphid and carbon tetrachloride Where infestation is general throughout a house or is serious in closets, it may be advisable to fumigate with hydrocyanic-acid gas, carbon disulphid, or sulphur, but none of these fumigation methods should be employed except by a person well informed regarding them. The foregoing remedies and others, such as cold storage, red-cedar chests, heat, and the treatment of infested floor cracks, are discussed in this bulletin.

Washington, D. C.

July, 1923

CARPET BEETLES AND THEIR CONTROL.

By E. A. Back, _Entomologist in Charge of Stored-Product Insect Investigations, Bureau of Entomology_.

CONTENTS.

Page.

Carpet beetles or "buffalo moths" 1 The common carpet beetle 2 The black carpet beetle 4 The varied carpet beetle 6 The furniture carpet beetle 7 Control measures 9 Naphthalene 10

Page.

Control measures--Continued. Paradichlorobenzene 10 Camphor 10 Red-cedar chests 11 Cold storage 11 Fumigation 11 Miscellaneous control measures 12

CARPET BEETLES OR "BUFFALO MOTHS."

THE so-called "buffalo moths" are not moths; they are beetles and very distinct from the true clothes moths. In this country there are six species,[1] at least, that attack museum materials and household fabrics, but of these only four[2] have proved serious household pests in America. All species are capable of subsisting upon dried animal remains, and thrive upon them perhaps as well as upon the fine fabrics of wool, hair, feathers, fur, and silk.

[1] _Anthrenus scrophulariae_ L., _A. museorum_ L., _A. fasciatus_ Hbst., _A. lepidus_ LeC, _A. verbasci_ L., and _Attagenus piceus_ Oliv.

[2] _Anthrenus scrophulariae_ L., _A. verbasci_ L., _A. fasciatus_ Hbst., and _Attagenus piceus_ Oliv.

Carpet beetles pass through life cycles, or generations, consisting of egg, larva or grub, pupa, and adult or beetle. These stages differ greatly in appearance. The beetles are broadly oval and about three-sixteenths to one-fourth of an inch long; black, but with this blackness often obscured by tiny red, orange, brown, yellow, or white scales which form color designs characteristic of the species. These scales, which are modified hairs, are easily rubbed off, revealing the black color of the body beneath. The larvæ, or grubs (as the larvæ of beetles are often called) are brownish or black and variously clothed with stiff hairs, as shown in Figures 1 and 8, or with a long tuft of hairs at the end of the body, as shown in Figure 5. Carpet beetles pass through not more than two generations annually, and more often only one, and there are records of certain individuals requiring much longer, even three years, to complete their growth. The following accounts are given of the four most important species.

THE COMMON CARPET BEETLE.[3]

[3] _Anthrenus scrophulariae_ L.

The common carpet beetle was known as _the_ carpet beetle in the years following its introduction into America when floors were more commonly than, now covered entirely with carpets that were tacked down along the edges, thus giving the larvæ an undisturbed shelter favorable to their development. Originally a pest in Europe, where it is still common, it was introduced into this country about 1874, probably at Boston and New York simultaneously. No stage of this common carpet beetle is longer than three-sixteenths to one-fourth of an inch. The general proportions of larva, pupa, and adult are shown in Figure 1. The rich reddish brown larvæ are clothed with stiff dark brown hairs which are longer around the sides, and still longer at the ends, than upon the back.

The larvæ feed upon carpets and woolens (Fig. 2), furs, feathers (Fig. 3), bristles, and silks. They remain secluded in dark places, hidden beneath carpets or in the folds of garments. They eat irregular holes in fabrics, but in carpets tacked to floors they are more likely to eat slits following cracks. They never cause a webbing on the fabric.

While most conspicuous in the Northern States, this carpet beetle is frequently found in the latitude of Washington, D. C, and southward Specimens have, recently been sent from Texas and Florida. In a Washington storehouse the contents of a trunk closed for several years were found badly damaged by the larvæ.

The following account[4] is just as applicable to-day as when written many years ago.

[4] Howard, L. 0., in Bulletin 4, new series, Division of Entomology, United States Department of Agriculture, pp. 58-59. 1896.

The adult insect is a small, broad-oval beetle, about three-sixteenths of an inch long, black in color, but is covered with exceedingly minute scales, which give it a marbled black-and-white appearance. It also has a red stripe down the middle of the back, widening into projections at three intervals. When disturbed it "plays 'possum," folding up its legs and antennæ and feigning death As a general thing the beetles begin to appear in the fall, and continue to issue, in heated houses, throughout the winter and following spring. Soon after issuing they pair, and the females lay their eggs in convenient spots. The eggs hatch, under favorable conditions, in a few days, and the larvæ, with plenty of food, develop quite rapidly. Their development is retarded by cold weather or lack of food, and they remain alive in the larval state, in such conditions and particularly in a dry atmosphere, for an almost indefinite period molting frequently and feeding upon their cast skins. Under normal conditions, however the skin is cast about six times, and there are, probably, in the North, not more than two annual generations. When the larva reaches full growth the yellowish pupa is formed within the last larval skin. Eventually this skin splits down the back and reveals the pupa, from which the beetle emerges later. The beetles are day fliers, and when not engaged in egg laying are attracted to the light. They fly to the windows, and may often be found upon the sills or panes. Where they can fly out through an open window they do so, and are strongly attracted to the flowers of certain plants, particularly the family Scrophulariaceæ but also to certain Composite, such as milfoil (_Achillea millefolium_). The flowers of Spiræa are also strongly attractive to the beetles. It is probable, however, that this migration from the house takes place, under ordinary circumstances after the eggs have been laid.

In Europe the insect is not especially noted as a household pest, probably owing to the fact that carpets are seldom tacked down. In fact, the writer believes that only where carpets are extensively used in this way are the conditions favorable for the great increase of this insect. Carpets once tacked down are seldom taken up for a year, and in the meantime the insect develops uninterruptedly. With the more general use of polished floors, and rugs which are often taken up and beaten, there is little doubt that the "buffalo bug" will eventually cease to be a household insect of importance. The insect is known in Europe as infesting museums, but has not acquired this habit to any great extent in this country. It is known to have this habit in Cambridge, Mass., and Detroit, Mich., as well as in San Francisco, Calif., but not in other localities. In each of these three cases it was imported from Europe in insect collections.

THE BLACK CARPET BEETLE.[5]

[5] _Attagenus piceus_ Oliv.

The black carpet beetle derives its common name from the black, unadorned color of the adult. Its larva is reddish or golden brown, long and slender, with a characteristic tuft of long hairs at the end of its body. It curls up and "plays 'possum" when disturbed. A glance at Figure 5 will be sufficient for the identification of this unique carpet-beetle larva.

Widespread in Europe and Asia, it first attracted attention in America in 1854. Since then it has become widely distributed throughout the United States, often being the most injurious of the carpet beetles, especially in the more southern States. It is the carpet beetle most commonly referred by housewives to the department for identification. It feeds upon household fabrics of wool, feathers, fur, hair, and silk, and also upon cereals and cereal products, seeds, and dried animal remains, hence has many opportunities for existence in warehouses and barns as well as in houses.

=The adult.=--The adult of the black carpet beetle is small, oval, and black, as shown in Figure 4. The adults are present in abundance only during the early summer. In a steam-heated building at Washington, D. C, large numbers of adults were present late in April and during May, but became rather scarce during the first part of June, although single adults were found as late as early in July. The adult flies readily and is often seen crawling on window panes and screens. It is during the adult stage that the black carpet beetle spreads most easily from house to house.

The female beetle lays small, white, fragile eggs upon fabrics, in floor cracks, or in any sheltered spot near its food. The length of life of the parent insect ranges from 3 to 35 days during April, May, and June. Seldom are adults found later than July, except in very warm storage houses.

=The egg.=--The fragile white eggs are very seldom seen, and hatch in warm weather in about 6 to 10 days.

=The larva.=--The golden brown larva, with short, stiff body hairs, and its long tuft of hairs at the end of the body (Fig. 5), attains a length of one-fourth of an inch, exclusive of the tuft of hair at the end of the body. When first hatched it is almost microscopic in size, but increases rapidly under favorable food and climatic conditions. As it grows it sheds its skin from five to eleven times, and possibly oftener. This is of interest, for frequently the cast skins are mistaken for the insect itself, thus unnecessarily alarming the housewife concerning the abundance of this carpet beetle. It required approximately one year for larvæ to become fully grown when fed upon casein. Larvæ hatching during early June and fed upon casein became full grown and transformed to the adult stage during the following April, May, and June. Larvæ fed upon woolen cloth and silk and flour and meal were still only partially grown at the end of one year, indicating that the black carpet beetle may require two years for its development. In India it has been found that certain of these larvæ may require from one to three years for growth.

=The pupa.=--In the pupa stage the insect is white, clothed with fine white hairs (Fig. 6), and helpless. The pupa stage continues from 6 to 16 days during early summer at Washington, D. C, and is seldom found at any other season of the year.

=Seasonal history.=--Since the greater part of the life cycle is passed in the larva stage, the facts previously mentioned indicate that the black carpet beetle may have only one generation each year, although it may require two or three years for the same development. From the observation of the writer, made in houses, warehouses, and in the laboratory at Washington, there seems little doubt that a very large percentage of the insects have one generation each year. Farther north, or under less favorable climatic and food conditions, a generation may require two or even three years. At any rate, the adults are on the wing during early summer and the eggs for new infestations are laid then.

THE VARIED CARPET BEETLE.[6]

[6] _Anthrenus verbasci_ L.

The varied carpet beetle is similar in shape to the common carpet beetle,[7] but is a trifle smaller. It is called the "varied" carpet beetle because the color pattern on the back of the beetle varies considerably with the arrangement of the white, brownish, and yellowish scales. Figure 7 presents a common arrangement of the scales. The underside of the body is thickly clothed with white scales. This insect is a European pest now well established in widely separated parts of the United States. It has been found more often perhaps feeding upon seeds in museums than upon clothing, though its larvæ do attack woolen goods, feathers, hair, and silks.

[7] _Anthrenus scrophulariae_ L.

The larvæ are not unlike other carpet beetle larvæ of the genus Anthrenus. In Figures 8 and 9 are shown the newly hatched and the mature larvæ. When unmutilated, they posses on each side at the end of the body three dense tufts of bristles and hairs. If suddenly alarmed, the larvæ erect these tufts and spread the bristles and hairs out so as to form beautiful round balls.

During late spring and early summer, when the insect transforms to the adult stage in greatest numbers, the adults are driven by instinct to seek the bright sunshine and the pollen of certain flowers. In this respect they are not unlike other species of carpet beetles, the adults of which may be found also upon flowers. Some think that Viburnum or Spiraea bushes planted near the house will lure carpet beetles from the house. It is probably true, however, that the beetles, before leaving the house, lay a large percentage of their eggs, so that the attraction the sun and flowers have for them is of so little practical value to the householder that it is not worth while to depend upon flowers to lure the adults from the house.

The varied carpet beetle in the adult stage flies about in tremendous numbers. During May, 1922, the writer could capture them by the thousands upon at least 30 species of flowers found in public gardens in Washington, D. C. Single white roses often attracted more than 100 beetles, while a single stalk of a common herbaceous Spiraea harbored more than 1,000 specimens. The beetles often fly in large numbers rather high above the ground. A gentleman[8] after painting a portion of the tin roof of his house during early May returned 24 hours later to complete the painting, only to find that during the interim an average of two varied carpet beetles to the square inch had become entangled in the fresh paint. The writer observed two adults fly into his city apartment in Washington through an open window during early March, 1922. These flights of adults are of extreme importance to the householder, because they emphasize how readily carpet beetles may spread from house to house during spring and early summer. Window screens will exclude all except the smallest specimens if they fit tightly, but the average removable screen does not fit tightly enough to prevent adult carpet beetles from crawling into the house between screen and window frame.

[8] H. S. Barber.

THE FURNITURE CARPET BEETLE.[9]

[9] _Anthrenus fasciatus_ Herbst.

The carpet beetle or dermestid[10] here discussed has had no common name, but may be called the furniture carpet beetle (Fig. 10). It, too, is a European pest introduced into this country. It has been reported from Algeria, Spain, Greece, southern Russia Mesopotamia, and the East Indies It was first recognized in America during 1911, from specimens sent the American Museum of Natural History, New York City, from an upholsterer in Augusta, Ga. The specimen were taken from the curled hair of furniture upholstered 12 to 15 years previous to 1911. Investigation indicated that the hair used in this furniture came from Russia. The pest was not again noted in America until April, 1915, when it was found seriously damaging an upholstered chair in the White House. Since then, particularly during the last several years, many pieces of furniture and mattresses in different sections have been reported badly damaged.

[10] So called because, like the other carpet beetles, it belongs to the family Dermestidae.

In all instances the furniture was upholstered with curled hair and moss, and in some cases the hair had been completely devoured by the larvæ, in association with smaller numbers of the common carpet beetle, the black carpet beetle, and the webbing clothes moth. (Figs. 11 and 12.)

This beetle is now well established in this country and is a most serious furniture pest. The adults eat holes through heavy leather and linen coverings, while the larvæ reduce the hair used in the upholstering to a mass of cast larval skins and ground-up hair. The hair then has the appearance of black gritty dirt which can be scraped up by the handful, if not by the pailful. When the larvæ become abundant in a piece of furniture they may drop to the floor and there feed upon rugs and other fabrics made of wool, hair, fur, or feathers. The larva; or grubs are seldom seen unless searched for, but the adults, because of their habit of flight during March to June (in Washington), leave the furniture and crawl about the furnishings and windows, and while hardly one-fourth of an inch long, are made conspicuous by the brown, white, and yellow scales that cover their bodies.

For a general impression of the appearance of the furniture carpet beetle see Figure 10. The adult may live several weeks. The female has been known to lay as many as 36 eggs in one day. Fortunately this species does not seem to be very prolific, since no adult has been known to lay more than 85 eggs. The eggs are small, white, easily crushed by brushing, and are laid in the nap of clothing. In furniture coverings of mohair, plush, and similar materials the eggs are tucked down in the pile, as shown in Figure 13. The eggs hatch during warm summer weather in from 12 to 15 days. The larvæ require the rest of the year for growth and do not transform to the adult until the following spring. The larvæ, however, do not all grow equally well, and some specimens may require only one year for development, while others may remain for considerable periods somewhat dormant, even in the presence of much food, and will not transform to the adult until much later, sometimes as long as one year after others, hatching on the same day, have matured.

CONTROL MEASURES.

The measures to be used for the control of carpet beetles depend upon the place in the house where the pest is causing injury. If carpet beetles are troublesome in trunks, chests, or closets that are not opened often, a good grade of flake naphthalene, paradichlorobenzene or camphor will give good results. If the trouble is in closets in daily use, beneath carpets or rugs, or in piano felts or upholstered furniture, these substances are of practically no value, and one must fumigate the house as a whole or in part with either hydrocyanic-acid gas, carbon disulphid, or carbon tetrachlorid, or use the still older, more tedious, and less effective means of control consisting in frequent search for and the killing of the individual larvæ and adults, and the treatment of floor cracks and similar hiding places with kerosene, gasoline, or benzine. The following materials and methods may be employed with satisfactory results:

NAPHTHALENE.