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Pest Information: Carpet Beetle

Identification

The larval form of carpet beetles are roughly 4–5 millimetres (0.16–0.20 in) in length. The body is covered in a pattern of alternating light- and dark-brown stripes. The body is usually wider at the back than at the front and also bears 3 pairs of hair tufts along its rear abdomen that can be used for self-defense.

Adult carpet beetles range from 1.7 to 3.5 mm (0.07 to 0.14 in) in length. Their dorsal surface has scales of two colours, whitish and yellowish-brown. White scales are condensed along the lateral margins of the pronotum. In addition, their antennae are 11-segmented with a club of 3 segments.

Life cycle

The Carpet Beetle has an unusual life cycle for an insect, developing from larvae to adult in 1–3 years, depending on the environmental conditions. Larvae hatch from eggs in the spring and early summer, often in the nests of birds (including those of the House Sparrow and House Swift) or around stored fabrics. Larvae feed on natural fibers throughout their development, eventually experiencing a dormancy period (also known as diapause) prior to pupation into the adult stage. The length of the dormancy appears to depend on environmental factors, with the most likely factor being length of daylight.

Adults emerge between late May and early August, flying to and feeding on the pollen of flowering plants.  During this period, mating occurs, eggs are laid, and the cycle begins anew.

Predators

Among the natural predators of the carpet beetle, one of the most well-studied is the wasp Laelius pedatus. Upon discovering a carpet beetle larva, a female wasp will land on the larva's dorsal side and attempt to line up its long, stinger for a paralyzing blow to the thorax. In response, the larva will erect long hairs on their abdomen and attempt to brush these hairs against the encroaching wasp. The hairs detach and stick to the wasp on contact, presumably causing some sort of irritation. Evidently, such irritation is not enough to deter an attack on the carpet beetle larvae, as the vast majority of attacks are bu the wasps are successful.

After a single successful sting, the beetle is permanently paralyzed. The entire process from landing to complete paralysis lasts approximately 40 seconds the wasp does not lay eggs immediately after the beetle is paralyzed, waiting as long as 24 hours before oviposition. During this time, she grooms herself, removing any hairs that might have stuck to her during the attack. During this lengthy process she appears to monitor the larva’s state of paralysis by repeatedly biting it and monitoring its reaction. Once sufficiently clear of hairs, the wasp creates a bare patch on the larva’s abdomen and lays 2–4 eggs. Eggs hatch in 3–4 days and the larvae feed on the beetle for 3–7 days, eventually killing the host. They then spin cocoons near the empty shell of the host, emerging some time later as an adult wasp.

Interaction with humans

The larvae of the carpet beetle is a common household pest. Adult beetles usually lay their eggs in air ducts, in closets, under furniture, or under baseboards. Once hatched and until they pupate into adults, the larvae hide in dark, undisturbed areas and feed on organic material. The larvae are thus responsible for the damage of various items, such as furniture, clothing, blankets, furs, and carpets. Collections of specimens, especially of insects, are also vulnerable to attack, making carpet beetles a common pest in museums. Infestations can be prevented by regular vacuum cleaning, dry cleaning or airing clothing outside, placing naphthalene balls in closets, and removing abandoned bird and insect nests attached to the building.  Signs of an infestation include the presence of damaged articles, molted larval skins in dark areas, and an abundance of adult beetles near windows.

If you suspect that you have an infestation of carpet beetles, contact Cain Pest Control for your free estimate.