I have had more calls than usual recently regarding Carpet Beetles. Therefore I have written this blog on the subject.
There are three common species of carpet beetles found in the UK. These are the varied carpet beetle, the museum beetle and the common carpet beetle. The varied carpet beetle is most commonly encountered by pest controllers in the UK. So this species will be the focus of this blog. Carpet beetles get their name from the fact that the larval stage of the life cycle are pests of woollen materials, fur, leather and carpets. They have outstripped the clothes moths as the major textile pest in Britain. In ‘the wild’ the larvae are common in bird’s nests. The adult beetles are capable filers and feed on pollen.
The varied carpet beetles are so called because of the speckled appearance of the scales covering the hard wing cases of the adult beetle. The adult beetle resembles a miniature lady bird in size and shape. These scales are black, white and yellow / brown in colour on the upper surface. This gives rise to the variegated appearance. The scales rub off easily and older individuals are often partially devoid of scales, showing the shiny black wing cases.
The larval stage is about 4 millimetres long. It is beige in colour and covered in tiny hairs. This covering of tiny hairs gives rise to the common term ‘woolly bear’. In common with other insects bearing hairs, skin contact with them can cause skin irritation. Many of the calls I receive about carpet beetles are from office staff who are encountering the adult beetles falling from the ceiling. Closer investigation usually identifies that the larval stage is feeding on dead cluster flies which have accumulated in the ceiling void.
In this case the carpet beetles are a secondary pest. Cluster flies are a topic for a future blog, but the cycle of cluster flies hibernating in ceiling voids should be addressed.
A residual spray treatment of insecticide to affected areas will kill the larval stage. It is this larval stage which causes the damage. Where appropriate, an insecticidal mist treatment can also be carried out to kill the adult stage. Jackdaws nesting in the loft has also been a common source of carpet beetles inhabiting a property. For this reason it is often necessary to investigate loft and roof areas for bird nests.
If materials are heavily infested, they should be destroyed. Infested areas should be thoroughly vacuumed, concentrating on removing larvae and debris from crevices. Any other possible primary source should be investigated, as described above. An application of a residual insecticide should then be made for affected areas. Non toxic desiccant dusts may also be effective for smaller infestations.