Carpet beetles Anthrenus spp

There are three common species of carpet beetle: Anthrenus verbasci, the varied carpet beetle, Anthrenus museorum, the museum beetle, and Anthrenus scrophulariae, the common carpet beetle. The varied carpet beetle and the museum beetle are the most commonly encountered by pest controllers.

The varied carpet beetle Anthrenus verbasci


Key features

The adult beetles, which are around 3 mm in length,have a speckled appearance which arises because of the many scales which cover the elytra and the prothorax. These scales are black, white and yellow / brown in colour on the upper surface and they give the beetle a variegated appearance, hence the common name, and a white appearance on the lower surface. As the beetles age these scales are often partially or totally rubbed off and the beetles then take on an even more mottled appearance. The antennae have eleven distinct segments with a three-segmented club.
The larvae of Anthrenus have a characteristic appearance, being covered in well developed hairs arranged in many tufts positioned at the intersegmental folds, giving rise to the common name for these larvae, “woolly bears”. At the posterior end of the larva there are three bundles of golden coloured hairs. The hairs, when inspected closely, can be seen to be segmented and have a sharp arrow-like head at the end.The larvae grow from around 1 mm when they first emerge from the egg to around 5 mm when fully grown.

Biology

The female beetles lay around 35 to 100 eggs in batches within the larval foodstuff. The eggs are small (0.2 to 0.5 mm long). white and are frequently “stuck” by a secretion from the female accessory glands to the fabric of the material in which they have been deposited. The larvae emerge from the eggs and start feeding. The larvae are repelled by the light and as a result as a result burrow deeply into their food. As they grow they moult and the cast skins are frequently found amongst the feeding larvae and this often gives the impression of a larger population than is, in fact, present.
Larval life is greatly dependent upon the quality of the food it is feeding upon. If the larvae have had periods in which they have fed well, they are capable of surviving prolonged periods without food – many months in fact.
Once fully grown the larvae pupate within the last larval skin and from the pupa emerges the adult.
There is often a gap between the development of the adult in the larval skin and the emergence of the adult; this can often extend to a month.

When the adults emerge they feed on the pollen of garden plants such as roses, viburnum and many other bushes. Indoors, adults may be found on windows from March to September.

Larvae may live in the nests of birds, insects and mammals.

In common with other insects, development times are influenced by temperature, relative humidity, moisture content, quantity and quality of food. The following figures are therefore only a guide.

Number of days spent as:

  • Egg
  • 14 – 31
  • Larva
  • 220 – 320
  • Pupa
  • 10 – 30
  • Adult male
  • 14 – 30
  • Adult female
  • 15 – 45

Egg to adult at room temperature averages 250 – 350 days.

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