Carpet beetles identification guide

Identification

There are three native species in Britain of the Anthrenus genus, of which the varied carpet beetle, Anthrenus verbasci, is a common house and museum pest.

It is a small (1.5-3.5 mm) and round beetle with elytra (wing cases) clothed with white, golden-yellow and black scales forming a variegated pattern of white, orange and black patches. The legs are black. The head is small and mostly kept hidden beneath the the upper part of the thorax (the beetle's mid-body). The eyes are large and black. The antennae are clubbed, with the three top antennal segments forming the club and the two bottom segments also bulged.

The closely related museum beetle (Anthrenus museorum) is predominantly black with some orange spots, and has rust-coloured legs.

The larvae of carpet beetles are called woolly bears because of their bodies being covered in hairs. Thelarva has unevenly coloured tergites (the plates on its back covering its body segments); the ones in the middle are lighter brown, the three thoracic tergites just behind the head and the very last four abdominal tergites are visibly darker. The head is always light brown to orange, even when the tergites are quite dark.

The last three abdominal segments carry thick tufts of special hairs growing backwards which are characteristic of the genus Anthrenus.

The larva of the closely related Museum beetle A. museorum is different in that all of its tergites are evenly coloured dark brown, and its head is also dark brown.

Due to the small size of the larvae (4-4.5 mm) and because the differences between different stages of the same larva may be larger than differences between species, larvae are reliably identified only in their latest stage. Even so, separating related species is impossible without very powerful microscopes.

Distribution and habitat

A cosmopolitan species, the varied carpet beetle can be found in Europe, North America, Australia, etc. It is a native, long-established species in Britain, and the most common of the genus Anthrenus here. It is more common in the London area and the southern counties.

The larvae are usually domestic pests of woollen goods or museum pests, but also live in nests of birds and mammals. The adults visit flowers to feed on pollen and nectar, and in houses are often found on windowsills trying to get outside. It is also occasionally imported into Britain, mainly on dried fruit and nuts.

Life cycle

Like other insects, varied carpet beetles pass through four different stages: egg, larva, pupa and adult. The females lay their eggs on or near a food source: materials containing chitin and keratin. Periods of larval growth are followed by a diapause (resting period) which may help the beetles living outdoors to synchronise with the seasons. Thus, adults will emerge usually in the warmer months when their preferred food - pollen - is available. The larvae need a temperature of 15-25 °C to develop. In winter, the larvae enter a resting period (diapause).

Outside. the cycle takes two summer seasons for the full development of adults. Pupation takes place in the second spring. However, indoors, the whole cycle may complete in a year. The adults live between two and six weeks.

Damage and control

The larvae of carpet beetles are voracious feeders and can cause considerable damage to woollens and to dried insect and mammal collections. They will not feed on entirely synthetic fabrics. The varied carpet beetle is the only British species of the genus Anthrenus which is found in food stored products as well.

Clothing and carpets affected by the larvae of these beetles can be recognised by small, clean holes which are not accompanied by strands of silk webbing (as is usually the case with clothes moth infestations), but have powdery, dust like droppings associated with them. The cast - transparent skins shed by the larvae - are also a conspicuous sign of infestation.

Prevention is clearly more desirable than coping with a large infestation, which by the time it is discovered has already caused some damage. Cleanliness within buildings is important as larvae can thrive out of sight and undisturbed, eg behind skirting boards, in the pile of woollen carpets (particularly close to skirting boards), in fibres and other organic dust between floor boards, and in the vicinity of spiders' webs, feeding there on any dead insects.

Such infestations can usually be prevented by regular use of a vacuum cleaner. They can also be destroyed by applications of proprietary insecticides or, where feasible, by putting affected items in bags for a day or two in a deep freezer (at -18 °C).

Because birds' nests in roofs can act as important sources of infestations, these are best removed and destroyed. Cavities attractive to nesting birds should be blocked, eg by wire netting. Woollens and other natural fibres should be cleaned and stored within securely fastened plastic or polythene bags.

The two-spot carpet beetle (also called the fur beetle) is one of the commonest species of carpet beetles in Britain. Its larvae are often found in old houses associated with birds’ nests. It is also a well-known pest of natural history collections.

Identification

The adult is a beetle with an elongated oval body, 4.5-6 mm long, very dark brown to black with two white spots on the wing cases. The body surface is clothed with microscopic pale hairs, some of these forming two small white spots near the centre of the wing cases, which give the beetle its characteristic appearance. The base of thorax (the middle section of the beetle) is also covered with white hairs. The antennae are clubbed, with males having one very long last segment. Females are larger than males.

The larva of the two-spot carpet beetle is up to 6.5 mm long when fully developed, torpedo-shaped, tapering from head to the end of abdomen, which continues with two long orange tufts of hair. It superficially resembles a very dark silverfish. The segments are very visible, which give the larva a banded appearance, with darker stripes wider than the lighter ones. Its colour is golden yellow to brown, with golden yellow hairiness and a scaly down of the same colour on thorax and abdomen segments. Larvae of other Attagenus species are very similar.

Distribution and habitat

A cosmopolitan species, the two-spot carpet beetle can be found in Europe, North America, Australia, etc. It is a native species in Britain, and the most common of the genus Attagenus here. It has been recorded throughout the UK, but it is regarded as a pest mainly in the southern half of England and Wales.

Adult beetles fly readily and in the wild can be seen from March to September feeding on nectar and pollen of a wide range of flowers such as hawthorn and meadowsweet shrubs.

The larvae are naturally found on birds’ nests and feed on feathers, droppings, and the remains of dead insects such as flies and wasps. From birds’ nests, they often infest households and warehouses. They can destroy natural history specimens, and sometimes wool and fur textiles.

Life cycle

Adult beetles live actively for three months. They fly in warm weather and feed on nectar and pollen of flowers, although they can lay viable eggs even if they don’t feed at all. The females lay eggs in cracks and crevices near a food source, such as a bird’s nest.

The newly hatched larvae are less than 0.5 mm long and very narrow. As they grow in size, they shed their skins (moult) a number of times. The whole cycle can take from six months to three years, depending on how much food is available and on temperature. They need 15°C to 30°C to develop.

The largest larvae finally pupate and after two weeks the adults emerge and typically hibernate, then become active in spring. Larvae in different stages can be found all year round. If plenty of food is present, successive generations can be produced without adults ever leaving the area, feeding or drinking.

Damage and control

The larvae feed on products containing keratin: wool, fur, feathers, skins, leather, silk, and dried insects. Occasionally, plant materials such as cereals and fibres can be attacked. They can cause damage to large clothing stores, boring holes in fabrics, starting at the seams.

This is one of the most dreaded museum pests, as the larvae can destroy collections of birds, mammals and insects. However, in the wild these larvae play an important role in recycling bird and insect nests, dead mammals, birds, insects, droppings, etc. The adults do not produce damage, but because they are able to fly they can spread an infestation to new households.

Prevention is clearly more desirable than coping with a large infestation, which by the time it is discovered has already caused some damage. Cleanliness within buildings is important as larvae can thrive out of sight and undisturbed, eg behind skirting boards, in the pile of woollen carpets (particularly close to skirting boards), in fibres and other organic dust between floor boards, and in the vicinity of spiders' webs, feeding there on any dead insects.

Such infestations can usually be prevented by regular use of a vacuum cleaner. They can also be destroyed by applications of proprietary insecticides or, where feasible, by putting affected items in bags for a day or two in a deep freezer (at -18°C).

Because birds' nests in roofs can act as important sources of infestations, these are best removed and destroyed. Cavities attractive to nesting birds should be blocked, eg by wire netting. Woollens and other natural fibres should be cleaned and stored within securely fastened plastic or polythene bags.

The brown carpet beetle, also known as the vodka beetle, was introduced to Britain in the 1970s and is becoming more common as a pest of natural history collections and a minor household pest.

Identification

Adults have oval bodies 2-5 mm long and 2-2.5 mm wide, with a black base colour and dense hairs giving brown to reddish-yellow elytra (wing cases). The head and top part of the thorax (the beetle's middle section) are dark red-brown to black. The antennae and legs are reddish to yellow. Males have a very long last (11th) antennal segment, four times the length of the previous two segments together. The females are larger than males, with shorter antennae. There is one ocellus (simple eye) visible in the middle of the head.

The larva of the brown carpet beetle is up to 8mm long when fully developed, torpedo-shaped, tapering from head to the end of abdomen, which continues with two brush-shaped tufts of hair. It superficially resembles a very dark silverfish. The segments are very visible, which give the larva a banded appearance, with darker stripes wider than the lighter ones. Its colour is bronze-brown upperside and yellowish-brown underside, with golden yellow hairiness and a scaly pubescence of the same colour on thorax and abdomen segments. The larva avoids light. Larvae of other Attagenus species are very similar.

Distribution and habitat

The beetle originates from East Africa, from where it was accidentally imported to Russia where it was first observed in 1961. From there, it spread to different parts of Europe, including Britain. It was found here first in a small area around London, but it is now becoming more common in England.

It is a pest of natural history collections and a household pest. In nature it lives in birds’ nests and bats’ roosts, but it has became a synanthropic species, meaning it prefers to live in and around human dwellings. It has been recorded living on carpets, fluff on floor and on dead dry insects. It has also been found living in stored products in Africa and Europe. The larvae feed on a variety of materials containing keratin, such as wool, fur, hide, feather, etc. It is a warmth-loving species, so it depends on central heating for survival in Northern Europe.

Life cycle

The adults can live without feeding, but the larvae depend on dry substances of animal origin to develop.

The optimal conditions for the development of Vodka beetles are: 24°C temperature, 70-80% relative air humidity and plentiful food supply. In these ideal conditions, the female lays 30-50 eggs in small holes or other hiding places, the eggs hatch in 10 days, the larvae complete their development in 3 months after which they pupate and then emerge as adults in 8-13 days.

In real situations, the development may be much slower, the life cycle varying from 6 to 18 months. The larva molts its skin 12 times during the whole cycle. In permanently heated premises in Europe both adults and larvae can be found year round, but adults are more common from March to September.

Damage and control

The adult beetles are mostly diurnal (active during the day) and mobile, being able to fly and colonize new areas. They are often found on windowsills, seeking light, and also seeking food sources for the larvae, where females will lay their eggs.

The signs of brown carpet beetle infestation are damage to museum specimens, carpets, clothing, etc. and the frass (the larvae's extrement) resulting from feeding. The skins caste off by larvae after many molting events are another sign.

The damage is done by the larvae, which attack various organic materials containing keratin. Serious damage occurs when there is a massive, undetected infestation which can destroy entire museum collections or stored clothing and carpets. Stored food may be contaminated by excrement.

Preventing an infestation is the best way to avoid damage. Brown carpet beetles can be monitored with sticky traps, pheromone lures and larval food monitors. Quarantine is an important preventative measure when moving objects between collections or houses. Maintaining a strict hygiene by cleaning and removing potential food sources like fluff, feathers, etc. from inaccessible places such as between floorboards will prevent an infestation. In museum collections and storage facilities, maintaining low temperature and air humidity will prevent or slow down larval development.

If an infestation has occurred, it can be controlled by physical measures such as discarding infested items, vacuuming and brushing. When possible, deep freezing specimens or infested objects should be carried out to kill larvae and eggs.

Chemical control involves application of insecticide, fumigating, gas treatment, etc.

More information

Download this information as PDFs:

• Varied carpet beetle (PDF 359KB)
• Two-spot carpet beetle (PDF 243KB)
• Brown carpet beetle (PDF 169KB)

Elsewhere on the internet:

• Royal Entomological Society Handbooks for the Identification of British Insects Vol. 5 Part 3. Adults and Larvae of Hide, Larder and Carpet Beetles and their relatives (PDF 1.69MB)
• Info sheets from MuseumPests.net:
  • Brown carpet beetle/Vodka beetle (PDF 189KB)
  • Varied carpet beetle (PDF 190KB)