Carpet Beetle

The varied carpet beetle probably gets its common name because there is great variation in the color pattern on its dorsal surface. This species is known to cause dermatitis in humans. It is worldwide in distribution and is found throughout the United States.

Recognition

Adults about 1/16-1/8” (1.8-3.2 mm) long. Body black, with pattern of yellow and white scales on pronotum and elytra (wing covers), 2 transverse zigzag bands of white scales bordered by yellow scales on elytra; scales elongate, 2-3 times as long as broad; lower/underside of body covered with grayish yellow scales. Antennae short, with 3-segmented, compact club. Posterior end of elytra evenly rounded. Abdominal 5th sternite broadly and deeply emarginate (notched) apically. In addition, body oval, head more or less concealed from above, with a median ocellus, and tarsi 5-5-5 .

Larval length up to ¼” (4-5 mm). Stout, widest posteriorly. Color dark brown to black. Covered with brown hairs; with tufts of spear-headed hairs (hastisetae) arising from membranous areas on the sides of abdominal segments 5-6-7 pointing towards the rear and converging towards the center, heads of spear-headed hairs of hind tufts equal in length to combined length of 7-8 preceding segments. Antennae with segment 2 less than 2.5 times as long as broad. Abdominal sternites entirely membraneous.

Similar Groups

  1. Carpet beetle (anthrenus schrophulariae) with brick red scales along midline of elytra (wing covers).
  2. Furniture carpet beetle (Anthrenus flavipes) with pronotum and elytra patterned with white, yellow, and brown scales, underside of body pure white, posterior end of elytra with shallow notch at midline.
  3. Other dermestids (Dermestidae) with less compact antennal club of usually more than 3 segments, hairs on dorsal surface somewhat flattened but not scalelike, and/or 5th abdominal sternite not deeply notched apically.
  4. Poderpost/deathwatch/anobiid beetles (Anobiidae) with antenna longer, if clubbed, then club asymmetrical (lopsided).
  5. Other beetles with oval body form lack a median ocellus and/or lack scalelike hairs.

Damage and Signs of Infestation

Fabrics typically have much surface damage and holes here and there, but larvae can cause large irregular holes in material. Furs and brushes have mostly the tips of hairs damaged, leaving uneven areas. With museum insect specimens, the accumulation of fine powder/frass beneath the specimen is often the only indication of these beetle’s presence. Larval caste/molt skins are often present. Frass/droppings are minute, irregular in form, often the color of the material being damaged. The larvae may burrow through packaging materials when seeking food.

Biology

Females do not always lay their eggs on larval food material. The eggs hatch in 17-18 days. The larval period ranges from 222-323 days but may last up to 623 days under Adverse conditions of temperature, humidity, and food, and requires an average of 7-8 molts (range 5-16). The larva pupates in the last larval skin and pupation lasts 10-13 days. Developmental time (egg to adult) usually requires 249-354 days at room temperature, but may take as long as 2-3 years depending on temperature and food. Adult males live 13-28 days whereas, females live 14-44 days.

One case of dermatitis occurred in a man over a 5-year period due to hypersensitivity to an infestation in his bedroom carpet. Inhalation of large quantities of the larval spear-headed hairs may cause pulmonary irritation; Anthrenus spp. Are known to cause this condition.

Habits

Varied carpet beetle larvae feed on a wide variety of animal and plant products. Animal-origin materials include woolens, carpets, furs, hides, feathers, horns, bones, hair, silk, fish meal, insect pupae, and dead insects. Plant-origin materials include rye meal, corn, red pepper, cacao, cereals, etc. Their favored foods are insects and spiders which makes them a major pest of museum collections and buildings with cluster fly, boxelder bug, etc. problems.

On fabrics, larvae tend to surface graze but are quite capable of making small or large irregular holes. On furs and bristles, they damage mostly the tips leaving uneven areas. On dead insects, they typically feed from within and the accumulation of fine powder/frass beneath the specimen is usually the only indication of their presence. The larvae may burrow through packaging materials to get to the contained food.

Adults are found outside during warm weather. They are often found on flowers, particularly in the spring and especially on spiraea spp., where they often eat the pollen. Females seek out the nests of bees, wasps, and spiders as oviposition sites, as well as bird nests. Inside, adults are often found at windows during the spring.

The primary breeding areas are quite diverse and may include obscure or unusual places such as wall/ceiling voids where yellowjackets, honey bees, etc. lived or where cluster flies, boxelder bugs, etc. overwintered, rodent bait left in attics, crawl spaces, or basements; wasp and hornet nests in attics, under eaves, around windows, etc.; dead lint and hair accumulate; animal trophies or rugs; insulation which contains animal hair; dead animals in the chimney flue; etc. In such places, the larvae feed on the animal and/or plant material present.

The larvae tend to wander about and can be found far from the primary infestation. When disturbed, the larvae erect their hair tufts and spread the bristles and hairs, forming a ball.

Adults hatching from indoor pupae avoid or shun light until egg laying is mostly complete, and then become attracted to light. Most outdoor adults show an attraction to light.

Control

The key to controlling varied carpet beetles is to find the primary source(s) of infestation and eliminate it/them. Besides the obvious clothing, furs, drapes, carpeting, and stored products, it may be necessary to check for the more unusual places such as those listed above. Ask the customer about both current and past occurrences of flies in the winter, boxelder bugs, rodent problems, birds nesting on/in the building, etc.

The thorough inspection should be followed by good sanitation practices, and pesticide application when required. Museum specimens may be treated with heat and/or cold if applicable (be careful of possible damage to specimens) or with fumigants. Refer to the control section under the general treatment of fabric and paper pests for details.