Extremely common, but Unfamiliar
Carpet beetles, hide beetles, skin beetles, and dermestids. All these names describe members of the insect family Dermestidae. The meaning of Dermestidae gives a pretty good idea of the habits of these insects. Derma means skin; este, means to consume; and idae refers to members of the family. We can surmise dermestids are members of a family of insects that consume skin. How gruesome indeed!
In the U.S., there are about 120 species of dermestid beetles.
Outdoors, the larvae of some dermestid species help clean up the environment. Being scavengers, they feed on animal protein: mummified skin and flesh, hair, fur, feathers and even dead insects. Very few organisms feed on hair or fur because keratin, the protein in hair and feathers, is very stable and indigestible. But carpet beetles have enzymes in their digestive tract which digest keratin. This makes them very unusual in the animal world.
Sometimes dermestids can help with criminal investigations. Forensic entomologists will look for dermestid beetles at crimes scenes when trying to determine the time of death. Dermestids generally show up late in the decomposition process, when the corpse begins to dry out.
Museum curators know dermestid beetles all too well. Because dermestids can devour museum specimens, precautions must be taken to prevent damage to museum collections. But, their habit of feeding on animal protein can also be useful, as colonies of dermestids are used to clean the flesh and hair from bones and skulls.
Adult beetles are small and oval, and have knobbed antennae. They range in size from 1/16 inch (varied carpet beetle) to 3/8 inches (larder and hide beetles). Some species have brightly-colored scales on their body. Dermestid larvae usually have a wedge-shaped body covered with hairs, sometimes with longer tufts of hair (setae) on the back end. Size depends on each species, but they are usually less than 1/2-inch long.
Adults typically overwinter in cracks and crevices and become active in springtime. Females may enter homes or structures seeking food to lay eggs on. After hatching, larvae develop through 5-16 instars, depending on species. Cast skins from larval development are often found near the food source and may be the only signs of dermestids when damage to fabrics is noted. Pupation occurs in their last larval skin. Adults that emerge must feed on pollen, so beetles trapped indoors are often found in window sills or attracted to lights, perhaps because they are trying to get outdoors.
A few dermestid larvae have expanded their food preference and feed on plant proteins. They are often found feeding on flour, grains, nuts, seeds, and spices. Some even feed on silk and cotton.
Because they can digest wool and silk, dermestids can be a real nuisance in the home, where they may chew holes in sweaters and blankets. In Nebraska, carpet beetles (dermestids) usually damage woolens more often than clothes moths. In more humid states, clothes moths are a more common problem. Dermestids are often found in the bedroom, where hair accumulates in and around the bed or in the closet where woolen garments are stored. It is usually the larva or cast skins that are found. When people are checking bedrooms for bed bugs, dermestids are the most likely (non-bed bug) insects found.
Because dermestids feed on accumulated pet hair and feathers, they may be found in areas where pets sleep and be more of a problem when families have indoor pets.
Where do they come from?
Carpet beetles are exceptionally common indoors and some species are so small, they enter through window screen. Common reservoirs for dermestids are bird and rodent nests and old bee and wasp nests, where dermestid larvae feed on hair, feathers and/or dead insects.
The primary way to manage dermestids is to reduce their presence or potential food by regular sanitation practices. Regular, thorough vacuuming, and cleaning of bedrooms and closets where woolens are hanging, can be helpful. Damage to woolens usually occurs in the summertime, so removing woolens from closets in the spring, drycleaning them, and storing them with moth crystals will be helpful until fall. In the pantry, throw away infested foods and clean shelves to remove particles of food. Keep flour and other food items, including spices, in sealed, glass containers.