What Are Dermestes spp. Beetles?

This is a term which covers a range of very similar insects, the most common of which, in Glasgow, is Dermestes peruvianus. The name Dermestes is of Greek origin and means “to devour a skin” which is why some of the beetles in this genus have names such as hide beetles, carpet beetles and larder beetles.

The Dermestes spp. beetle, with which we are most familiar in Glasgow, was, at one time, a significant pest of stored food products. As methods of food production, storage and distribution improved they have been largely eliminated as stored product pests and have adapted very well to the domestic environment.

This beetle’s life cycle is egg, larva, pupa, and adult. You are most likely to see this insect in either its larval form or adult form or find shed larval skins. As these two stages of the insect’s development bear absolutely no resemblance to one and other some people think they have two separate infestations in their home. Consequently we will describe their appearance separately.

Do you want to know more about the larval stage?

About 12 days after the adult female has laid her eggs, in the vicinity of a suitable food source, the larvae hatch. The larvae moult 5 or 6 times depending on whether they are male or female. They have a voracious appetite and eat constantly (this is their equivalent to the teenage years in humans) until the next to last moult when they begin to seek a suitable place for pupation.

The larvae vary between 11 and 13 mm and are darkish brown with lighter coloured bands around its caterpillar-like body and they have two curved spines on the last visible body segment.

Do you want to know more about the adult stage?

When the larvae reach the last stage of their development they pupate. This pupal stage normally lasts between 3 to 7 days when, as a caterpillar becomes a butterfly, the adult insect emerges. The adult is dark brown in colour and measures between 7 to 9 mm in length.

Health Significance

It is generally held that these insects pose no public health threat as they are not associated with the spread of any disease affecting humans. However it has been suggested that their presence in numbers can exacerbate asthmatic conditions in certain individuals and there is the possibility of them moving from contaminated areas to food storage or preparation areas.

Control

Dermestes spp. beetles are secretive and live in cracks and crevices at the wall/floor junction as well as below cookers and units. They are most likely to be found in the kitchen, as this is close to available food, but they can be found elsewhere in the house, such as soft furnishings, where children may spill food crumbs, in a sofa for example.

So the first level of control is household hygiene. This has two beneficial effects. It deprives these scavenging insects of a potential food source and, in the event of an infestation happening, it will be identified at a much earlier stage.

If you are unfortunate enough to find that you have an infestation of Dermestes spp. beetles you have two options:

• You can call in the services of a professional pest controller and we would recommend that you select a contractor who is a member of the British Pest control Association (B.P.C.A.). You can select your contractor from the Yellow Pages in the “Pest Control” section. If you live in rented accommodation, your landlord may assist with the cost of any treatment. The contractor should provide you with all the details of the product which has been used and advise you of any additional precautions which you must take.

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• You can undertake the treatment yourself.
   
  

In either case your first course of action will be to clean the house thoroughly, paying particular  attention to vacuuming the wall/floor junction, pull out the cooker and clear any food spillages/debris which you may find, and remove the kick plates from any fitted-kitchen base units and vacuum the exposed void areas.

If you are carrying out the treatment you will need to purchase a suitable crawling insect pesticide and apply it to the above areas. This may be obtained at garden centres and some of the major DIY stores and it is essential that you read, understand and follow all the instructions that come with the product which you select. As stated before, Dermestes spp. beetles are secretive but upon being exposed to pesticide they tend to come out into the open causing some people to believe that the treatment has actually made the infestation worse. Needless to say this is not the case and live larvae and adults may be seen for some time after treatment. As long as the pesticide is not disturbed, it will be effective for several weeks. So we would recommend that you try not to wash or vacuum areas, where pesticide has been applied, for as long as possible.