I have had more calls than usual recently regarding Carpet Beetles and so I have written this blog on the subject.
There are three common species of carpet beetle found in the UK, the varied carpet beetle (Anthrenus verbaci), the museum beetle (Anthrenus museorum) and the common carpet beetle (Anthrenus scrophulariae). The varied carpet beetle is most commonly encountered by pest controllers in the UK and 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, and 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 fliers and feed on pollen. In the picture below, the tip of one wing can be seen poking out from under the outer wing casing.
The varied carpet beetle is so called because of the speckled appearance of the scales covering the elytra (the hard wing cases as seen with ladybirds). These scales are black, white and yellow / brown in colour on the upper surface and give rise to the variegated appearance. These scales rub off easily and older individuals are often partially devoid of scales, showing the shiny black elytra.
The majority of calls I receive about carpet beetles are from office staff who are encountering the adult beetles, around two to three millimetres diameter, falling from the ceiling. Closer investigation usually identifies that the larval stage of the life cycle is feeding on dead cluster flies which have accumulated in the ceiling void and that 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. An insecticidal mist treatment of ceiling voids affected by carpet beetles clears the beetle problem temporarily, but to cure the issue for the long term the dead flies need to be removed.
That is not an easy task because of the presence of insulation lagging and the overall disruption caused to an otherwise tidy and organised office environment! Jackdaws nesting in the loft has also been a common source of carpet beetles inhabiting a property.
The larval stage is about 5 millimetres long, 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.
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.