Carpet beetles, which belong to the family of beetles known as dermestids, are pests in warehouses, homes, museums, and other locations where suitable food exists. In California, three species of carpet beetles cause serious damage to fabrics, carpets, furs, stored food, and preserved specimens—the varied carpet beetle, the furniture carpet beetle, and the black carpet beetle.
IDENTIFICATION AND LIFE CYCLE
All three carpet beetle species have similar life cycles (Table 1). Adults lay eggs on a larval food source such as woolen fabric or carpets or furs. Eggs hatch in about two weeks, and the larvae feed for varying periods, depending upon the species and environmental conditions; they prefer dark, secluded places. When ready to pupate, the larvae might burrow further into the food or wander and burrow elsewhere. They might also pupate within their last larval skin if no other shelter is available. Although larvae don’t make webs as clothes moths do, their shed skins and fecal pellets, which are about the size of a grain of salt, make it obvious where they have been feeding.
Carpet beetle adults don’t feed on fabrics but seek out pollen and nectar. They are attracted to sunlight, and you’ll often find them feeding on the flowers of crape myrtle, spiraea, buckwheat, and other plants that produce abundant pollen. However, you can accidentally bring these pests inside on items such as cut flowers. With their rounded bodies and short antennae, carpet beetles somewhat resemble lady beetles in shape.
Varied Carpet Beetle
The adult varied carpet beetle, Anthrenus verbasci, is about 1/10 inch long and black with an irregular pattern of white, brown, and dark yellow scales on its wing covers, or elytra. In older adults the scales that form this pattern wear off, so the beetles appear solid brown or black. Outdoors, female beetles search out spider webs or bee, wasp, or bird nests as places to lay their eggs. The nests and webs contain dead insects, beeswax, pollen, feathers, or other debris that can serve as larval food. Indoors, beetles deposit eggs on or near wool carpets and rugs, woolen goods, animal skins, furs, stuffed animals, leather book bindings, feathers, animal horns, whalebone, hair, silk, dried plant products, and other materials that can serve as larval food. Adults usually appear in spring or early summer; indoors, you’ll often find them near windows.
Furniture Carpet Beetles
When viewed from above, adults of the furniture carpet beetle, A. flavipes, are slightly larger and rounder than the varied carpet beetle. Coloration and markings vary, but the furniture carpet beetle generally has a mottled appearance due to the black spots that intersperse the white and dark yellow to orange scales on its wing covers. If these scales have worn off, the adults can appear solid black. Their undersides are white.
Larvae are white at first but darken to dark red or chestnut brown as they mature. In contrast to larvae of the varied carpet beetle, these larvae are broader in front and narrower at the rear. Larvae of the furniture carpet beetle feed on the same types of items as varied carpet beetle larvae.
Black Carpet Beetle
Adults and larvae of the black carpet beetle, Attagenus unicolor, are distinctly different from the carpet beetles described above. Adult black carpet beetles range from 1/8 to 3/16 inch long. They are shiny black and dark brown with brownish legs. Full-sized larvae can be as long as 5/16 inch and range from light brown to almost black. Larvae are shiny, smooth, and hard, while short, stiff hairs cover their body. Their body tapers toward the rear and ends in a tuft of long hairs. In California and other arid areas, the black carpet beetle is a more serious stored-product pest than a fabric pest.
Damage occurs during the larval stage of carpet beetles. Larvae feed in dark, undisturbed locations on a variety of dead animals and animal products such as wool, silk, leather, fur, hair brushes with natural bristles, pet hair, and feathers; occasionally they feed on stored products such as certain spices and grains. They don’t feed on synthetic fibers.
It’s not always possible to tell from the damage whether clothes moths or carpet beetles caused it, but in general carpet beetles are more likely to damage a large area on one portion of a garment or carpet while moth damage more often appears as scattered holes. Also carpet beetle larvae leave brown, shelllike, bristly-looking cast skins when they molt. These skins and a lack of webbing are usually good clues that carpet beetles are the culprits.