Dermestid Beetles (Carpet Beetles) Fact Sheet No. 5.549 Insect Series|Home and Garden by W.S. Cranshaw* General Appearance and Habits Dermestid beetles are probably the Quick Facts most common insects present found in Dermestid beetles go through four Colorado homes and buildings. They different stages in their development – an • Dermestid beetles are are scavengers that can feed on a wide egg, a series of immature stages known as common insects that likely variety of foods humans provide. Some a larva (larvae in plural form), a transition can be found in most any species of dermestid beetles develop stage known as the pupa, and the adult. home in Colorado. on materials of animal origin, including Most dermestid beetles lay between 2-4 dead insects, pet hair, lint, woolen dozen eggs over a period of a month or • Most dermestid beetles are items, furs and feathers. Clothing and scavengers that develop on household furnishings made of wool or materials of animal origin, fur are occasionally damaged by these including dead insects, pet insects and some of the more common hair, lint, woolen items, furs species are often called “carpet beetles”, and feathers. Some are reflecting their importance as a pest of known as “carpet beetles” woolen carpeting. Fabrics and carpeting because they can feed on made of non-woolen materials are not woolen carpets. damaged by dermestid beetles. • Some types of dermestid Other types of dermestid beetles beetles have larvae that primarily feed on grain or seed based Figure 1: Furniture carpet beetle adult and larvae. develop by feeding on grain materials. These are often found in Photograph courtesy of Clemson University/ or seed-based materials. kitchens and pantry areas where Bugwood.org. susceptible foods are stored and • Infestations within a home prepared. These types of dermestid typically originate from wild beetles may develop anywhere in populations of beetles that the building where crumbs of spilled move into homes during foods are present. They may also be warm months. associated with caches of food stored by rodents behind building walls. • Dermestid beetles in buildings are primarily managed by Dermestid beetles are commonly removing foods on which found outdoors as well as indoors. they develop, treating infested Outdoors their scavenging habits have items that are kept with heat an important role as they consume Figure 2: Larvae of a Trogoderma species larvae infesting stored grain material. Photograoh or cold to kill insects, and dead plant and animal materials; courtesy of Joseph Berger, Bugwood.org storing susceptible material in dermestid beetles are key players in insect-proof containers. the “clean-up” crew of insects that help recycle nutrients in natural systems. Infestations that do occur indoors may result from migration of insects from outdoor sites into buildings or through movement of infested food materials. © Colorado State University Extension. 1/00. Revised 1/18. extension.colostate.edu *Colorado State University Extension entomologist and professor, bioagricultural sciences and pest Figure 3: Varied carpet beetle larva feeding on a management. 1/2018 dead cricket. Photograph courtesy of Jim Kalisch, University of Nebraska and may wander a considerable distance in search of new food sources.

When larvae are full grown they transition to the pupal stage. The pupa occurs within the skin of the last stage larva. The pupal stage of a dermestid beetle lasts about 2-3 weeks and the adult then emerges.

Figure 4: Side view (top) of a Trogoderma Adult dermestid beetles have a Figure 6: Pupa of a varied carpet beetle. species larva; top view (bottom) of a discarded generally oval body form, and range from Photograph courtesy of Dave Shetlar, The larval skin of a Trogoderma species Photographs University of Ohio courtesy of Dave Shetlar, The University of Ohio about 2-5 mm in length. Many of the more commonly encountered species are so, with the eggs scattered among food found in homes. Adults are golden generally dark brown to black. However, material on which they can develop. tan to dark brown, oval-form, and some of the smaller species are covered about 3-5 mm in length. The larvae with colored scales of various patterns. Dermestid beetle larvae typically are quite active but avoid light and will hatch from the eggs within 1-2 weeks curl up and play dead when disturbed. after the eggs are laid. The larvae have Most dermestid beetles that occur Outdoors they feed on various types a generally fuzzy appearance, being within buildings also occur as wild of animal-produced debris and are covered in hairs. Their body form is populations in Colorado. The larvae feed frequently associated with animal generally elongated and in overall color on various materials of animal origin and nests. Indoors they may be feeding they are reddish or light brown. Some commonly occur in bird nests and animal on lint made of dead skin flakes, hair, species have distinct tufts or tails of hairs dens. Adult beetles may feed on the dead insects and similar materials. extending from the posterior. Like all pollen of plants, with flowers of Spiraea, There is one generation produced insects, the developing larvae repeatedly Viburnum and spurges among those that per year and the overwintering stage shed their “skins” (exoskeleton) as they are most commonly visited by dermestid is a nearly full-grown larva. Pupation grow – often a dozen times or more in the beetles. Presumably, most household occurs with the last larval skin. course of becoming full-grown. These infestations originate from these wild discarded larval skins retain a general populations when adult beetles fly The smallest dermestid beetles resemblance to a larva, may accumulate indoors and find suitable indoor food found in homes are in the genus around infested materials, and are often sources. Carpet beetles also may be Anthrenus. hese are typically about one of the more noticeable signs of a carried into a home on furniture and food 2-3 mm long and have a round dermestid beetle infestation. items that are infested. body form. Adults have colorful body patterning produced by scales The length of time it takes for The most common dermestid beetles of yellow, browns and white. The dermestid beetle larvae to develop varies in homes have an annual life cycle larvae are spiny, with a body that is very widely, and is dependent on things that is completed in a year. Adults and slightly narrower at the head end, such as temperature and the quality of wandering larvae are most commonly which is often tipped with a small tuft the food. Most of the common species encountered indoors during late winter of hairs. Species that occur within found in homes typically have a larval and early spring. homes in Colorado, in approximate period that lasts close to a year, but it order, are the varied carpet beetle (Anthrenus verbasci), furniture carpet can range from 3-4 months to nearly two Common Dermestid years. If a food source disappears during beetle (Anthrenus flavipes), and the insect’s development, the larvae Beetles found in Homes common carpet beetle (Anthrenus can survive for several weeks. Also, most Dermestid beetles occur throughout scrophulariae). dermestid beetle larvae are quite mobile, the state, both indoors and outside. Several species are nearly worldwide in distribution as they are commonly carried with stored food products. At least 39 species of dermestid beetles have been reported from the state, but only about a half dozen are commonly found in buildings.

Attagenus is a genus best represented by Attagenus unicolor Figure 5: Discarded skins of varied carpet beetle unicolor, the black carpet beetle, which Figure 7: 7 Black carpet beetle adult and larva. larvae following molt. is one of the most common dermestids Photograph courtesy of Clemson University/ Bugwood.org The larvae of these dermestid Prevention and Control beetles feed on a wide variety of The most important step to take plant and animal products and are to manage an existing infestation of common in abandoned bee and wasp dermestid beetles is to locate and nests. They are not very active and then eliminate any site where they are generally feed in a limited area so developing. Evidence of discarded accumulations of larval skins are often skins of larvae and living larvae are observed. Adults are most common in often what is most closely found late spring and can be seen feeding that can identify a site of breeding on nectar and pollen of various small Figure 5: Larva of a varied carpet beetle insects. Adult insects may wander a showing defensive hairs. Photograph courtesy considerable distance from breeding of Jim Kalisch, University of Nebraska sites. life cycle can be highly varied due to diet and temperature but Trogoderma For those dermestid beetles that species may continuously develop and develop on animal material inspection produce more than one generation should concentrate on areas where annually. lint and hair tends to accumulate: areas under carpets and along carpet Dermestes species are most edges; under seldom-moved furniture; commonly associated with meat- in floor cracks, registers and ducts; Figure 8: Varied carpet beetles adults feeding on Spirea pollen. based material (including dried pet and in folds of upholstered furniture. foods). These are moderate-sized Check stored woolen clothing, wool (6-10 mm) beetles of oblong form. flannel and yarn in attics, basements Most are generally dark colored but and closets. Items made of fur and one common species known as the hair, feathers and preserved animals larder beetle (Dermestes lardarius) has may also be sources that allow a wide yellow band with dark spots across the wing covers. The larvae are dark reddish-brown with a tapered body form. When full-grown they usually wander from the food source Figure 9: Varied carpet beetles. Photograph and tunnel to produce a pupation courtesy of Jim Kalisch, University of Nebraska chamber. They have strong jaws flowers. They are strong fliers and and have been known to excavate usually enter buildings in spring, often wood beams during this stage. The colonizing areas behind walls or attics overwintering stage is normally an where dead insects collect on which adult and they are strong flying insects Figure 12: Larva of a warehouse beetle, that are most commonly seen in late Trogoderma variabile. Photograph courtesy of they feed. One generation is normally Jim Kalisch, University of Nebraska produced annually with winter spent as spring and early summer. a late stage larva or pupa in a semi- dermestid beetles to breed. Other dormant condition (diapause). possible breeding sites are old animal or bird nests that may be attached to Dermestid beetles in the genus the building and collections of dead Trogoderma are also general insects around windows or behind scavengers but are often develop on walls. plant materials such as seeds, nuts, herbs, spices, and cocoa. Some For those dermestid beetles that are important pests of stored foods. may be developing on flour, grains, Adults are oblong bodied, about 3-4 nuts, seeds give particular attention mm long and generally dark bodied. Figure11: Trogoderma species of dermestid to areas where these types of food Wavy bands or faint patches mark the beetle. Photograph courtesy of Joseph Berger/ products have been stored for long wing covers of some species, and Bugwood.org periods. These food sources usually this is a feature of one of the most Some species of Dermestes will be in pantry and food storage common dermestid beetles found are used by museum zoology areas. However, dermestid beetles in buildings, Trogoderma variabile, departments and taxidermists to clean may also develop on grains and nuts known as the warehouse beetle. flesh from bones. These are often stored by rodents and squirrels in Larvae are elongate bodied and tend referred to as hide beetles because of nesting areas behind walls. to be lighter colored than most other their ability to feed on dried skin and dermestids. Like most dermestids, the hair. and dry-cleaning can be used to kill insecticides must be made strictly insects infesting clothing or fabrics. in accordance to label directions. Successfully disinfesting larger items, Most indicate that applications are either by deep freezing or heat, applied to cracks and crevices, such will require longer times to achieve as baseboard areas, corners, edges sustained temperatures penetrating of carpeting and other areas where into the material that can kill insects. lint and other debris accumulates. Several over-the-counter insecticides Once disinfested, storing food, that allow such use are sold through woolens, furs and other susceptible retail outlets and contain as the items in insect-proof containers can active ingredient either permethrin, effectively prevent further access by bifenthrin, deltamethrin, cypermethrin, dermestid beetle larvae and adults. tralomethrin and/or related Storing susceptible materials at low compounds. (Note: Household “bug temperatures (below about 40oF) also bombs” will not be effective against can prevent successful development of dermestid beetles.) dermestid beetles.

By periodically vacuuming up lint and hair, collections of dead insects Figure 13: Larder beetles. Photograph courtesy around window wells, and any spilled of Jim Kalisch, University of Nebraska grain materials most sites where dermestid beetles can breed will be Wherever a source is found eliminated. Vacuuming should give that allows dermestid beetles to particular attention to areas where reproduce, this should be removed lint accumulates and also to stuffed and destroyed. Objects that cannot furniture where food crumbs may Figure 15: . Duff millipede be discarded or destroyed, such as collect. Since dermestid beetles that woolen items or food that is minimally are picked up during vacuuming Duff Millipedes: A infested, can be disinfested by treating may continue to develop within household pest that may in a manner that kills all life stages of a the collected material, the bags or be mistaken for carpet dermestid beetle. This can be done by containers should be disposed if there beetle larvae freezing or heat treating. is any chance that the insect may be able to escape. Relatively small items infested Although larvae of dermestid beetles have a quite distinctive with dermestid beetles can be Most dermestid beetles fly and may appearance, the smaller species placed in a deep freezer that can enter buildings through sites such as somewhat resemble duff millipedes, drop temperatures below 0oF. Items cracks around edges of windows or which can be a source of confusion. consistently maintained at these low doors, through vents and openings Duff millipedes (Polyxenes species) are temperatures for three days or more under eaves, or through unscreened unusual millipedes with a stout, very can usually kill all stages of these doors or windows. Sealing buildings to hairy body but can be distinguished by insects. prevent these access areas can help their smaller size (1 mm), flattened fans reduce sources of new infestations. High temperatures can also be of hairs protruding from the hind end used to kill dermestid beetles in and, on very close inspection, several infested items. Exposure to above Chemical Controls more legs than the three pair present 130oF for several hours can kill on beetle larvae. Duff millipedes are typically found in forested areas dermestid beetles. Clothes driers Insecticides should only be used in where they feed on fungi, lichens and combination with efforts that provide decaying plant matter. Sometimes they a thorough cleanout of potential may migrate into homes in substantial breeding sites and vacuuming/removal numbers and cause nuisance of existing insects. Alone they will not problems, but are harmless. effectively manage dermestid beetles. In managing an existing infestation of dermestid beetles there may be some value in using insecticides to supplement control methods. In Colorado State University, U.S. Department of Agriculture and Colorado counties cooperating. CSU Extension nonfood areas household formulation programs are available to all without discrimination. No Figure 14: Larva of a larder beetle. Photograph of various pyrethroid insecticides can endorsement of products mentioned is intended nor is courtesy of Jim Kalisch, University of Nebraska be applied as sprays. Use of these criticism implied of products not mentioned.