The carpet beetle is a colloquial name given to a number of species of beetle classified in the Desmistidae family. Found all over the world, adult carpet beetles feed primarily on nectar from flowering plants. Their larvae feed on natural fibers and as such, are a common household pest species, frequently infesting and damaging clothes, textiles, carpets, and clothing.
“Any foolish boy can stamp on a beetle, but all the professors in the world cannot make a beetle.” — Arthur Schopenhauer
They were among the first species demonstrated by biologists to have an annual behavioral rhythm and the varied carpet beetle (Anthrenus verbasci) is commonly cited as a paradigm instance of circannual cycles in living organisms.
Because their larvae feed on natural fibers, carpet beetles are particularly problematic pests in museums. Carpet beetles will infest displays of insects, feeding on the chitin in their shells and wreak havoc on historical artifacts made from cloths and textiles. As such, carpet beetles are classified as a major pest risk for museums of natural history.
Appearance/Anatomy Of The Carpet Beetle
Carpet beetles have a squat spherical appearance, and their sizes range from the larger black carpet beetle (Attagenus unicolor) at an average of 5 mm to the small varied carpet beetle at 1.7 mm. The thorax is covered by a pair of hardened forewings called elytra which cover a pair of wings. On top of the elytra are scales that give each species of carpet beetle their characteristic color. The particular color differs with the species; all black for black carpet beetles and an irregular pattern of white, orange, and yellow for varied carpet beetles.
Carpet beetle larvae are sometimes called “woolly bears” in reference to their hairy appearance. The hairy appearance comes from the presence of dense clusters of setae that they use to grip and move across their environment. Interestingly, carpet beetle larvae of a particular species are generally larger than adult specimens of the same species, and most carpet beetle larvae are approximately 5 mm.
Behavior/Lifecycle Of The Carpet Beetle
Depending on their particular stage in life, carpet beetles consume different diets. Adult carpet beetles mostly just feed on the pollen and nectar of flowering plants. Adult beetles will flit from plant to plant, lapping up the pollen and nectar before moving to the next one. Carpet beetle larvae, on the other hand, consume a diet of natural fibers like keratin, the main structural component of animal hair, feathers, hooves, horns, and nails, and chitin, the main component of insect exoskeletons and fungal cell walls. Carpet beetle larvae will nestle in crevices where they feed off dead hair from animals, dead insect exoskeletons, cloths, and fabrics.
Every carpet beetle goes through 4 lifecycle stage: egg, larva, pupa, and adult. The incubation period for carpet beetle eggs can vary greatly with the temperature. For example, the varied carpet beetle has egg incubation periods as low as 12 days in favorable warm temperatures and up to 60 days in cold harsh weather. Once hatched, the carpet beetle enters the larval stage. The larval stage takes up the majority of the carpet beetle life. Carpet beetles generally take about 3 months to mature but can remain in their larval stage for up to 3 years depending on environmental factors like temperature and food availability. Most carpet beetle eggs are laid in animal nests or near stored fabrics so they have an immediate source of food when they hatch into larva.
“Every beetle is a gazelle in the eyes of its mother.” — Moorish Proverb
After the larval stage, the carpet beetle enters the pupa stage, during which it goes through its final maturation into an adult. Like the larval stage, the length of the pupal stage can vary greatly depending on environmental factors. Experiments with varied carpet beetle have shown that the length of the pupal stage can vary from 89 days in low temperature to just 9 days in favorable conditions. After the pupal stage, the carpet beetle becomes a fully mature adult specimen. Adults typically emerge from May to August and begin to feed on flowering plants. The average lifespan of an adult carpet beetle is about 2–3 weeks, during which the beetle mates and lays its eggs to start the cycle anew.
Carpet beetles were integral to the first scientific investigations of circannual cycles in living organisms. Carpet beetles exhibit an extremely robust internal clock that sets their yearly cycles, and this cycle continues even when the beetle is removed from external environments. Though the exact physiological mechanisms that realize biological rhythms are not well known, it is known that biological rhythms synchronize the beetle’s behavior to a periodic annual rhythm.
Carpet Beetles And Humans
Because they feed on natural fibers, carpet beetle larvae are a notorious household pest. Adult beetle who fly in domestic areas via vents or open window will lay their eggs in dark enclosed spaces, like closets, near pet spaces, under carpets, and under floorboards. Once the larva hatches they feed, causing damage to fabrics, furniture, clothes, and carpets. Carpet bug larvae can remain in the dim and dark for months, slowly feeding on fibrous material until they mature into the pupal stage. Setae from the carpet bug larvae can irritate human skin and cause welts to form that are often mistaken for bedbug bites.
“How we love sequestering, where no pests are pestering.” — Lorenz Hart
The particular diet of choice for carpet beetle larva makes them an especially annoying pest in museums. Museums frequently display dead specimens of animals and insect, and the carpet beetle larvae are drawn to the fur, hooves, horns, fur, and chitinous shells of the exhibits. They also can destroy historical artifacts made from fabric like old tapestries and clothing.
Domestic infestations of carpet beetles can be prevented by regular vacuuming of carpets and airing out of fabrics. Keeping floors and carpets clean from pet hair or dander removes a potential food source and can prevent an infestation from taking hold. Naphthalene mothballs are also effective against carpet bug larvae as well as various insecticides and scent traps. Mostly though, a routine regiment of cleaning interior fabrics and removing animal or insect nests from exterior places can greatly reduce the chances of carpet beetle infestation.