Dermestes lardarius Linnaeus, 1758
POLYPHAGA Emery, 1886
BOSTRICHOIDEA Latreille, 1802
DERMESTINAE Latreille, 1804
Dermestes Linnaeus, 1758
Dermestes Linnaeus, 1758
A generally common pest species with a worldwide distribution, it was once common in both domestic and commercial premises in the U.K. but is now sporadic following improved food storage and preservation techniques. Adults occur year round throughout England and Wales but more rarely so in Scotland. In domestic premises they tend to occur continuously over several years due to the difficulty in finding and removing the food source and larvae. The larvae develop in a wide range of animal products e.g. dried meats, fish, pet foods, skin and feathers, dead insects and sometimes high protein plant materials e.g. grains. Although the adults may be active throughout the year inside they may also overwinter outside in bark crevices, old nests and other sheltered situations, and during the summer occasionally in avian and hymenopteran nests. They become active in early spring, flying from overwintering quarters into buildings in search of host material, and will often lay eggs among accumulated dead insects or occupied avian nests. In temperate climates the females oviposit through the spring and into the summer, each laying more than 100 eggs near or on a food source. The eggs hatch after about 12 days and, if necessary the larvae will roam in order to find food, meat products are preferred, especially those that are beginning to decay, but basically most animal products will be consumed and larvae will often live in cracks in floors or cupboards etc. or among accumulated dust or detritus in food storage situations. They feed continuously until the penultimate moult; males will moult 5 times while females moult 6 times, and the cast skins may be found in numbers by careful inspection of suspected sites of infestation. When ready to pupate they will bore into just about anything handy in order to form a secluded puparium, preferring the food source itself but also utilizing plaster, wood, fabrics, lead and even chewing through tin sheet. The pupal stage is brief, from 3-7 days depending on temperature and moisture, and under good conditions the entire life cycle may take 6 or 7 weeks. Adults are long lived and in tropical areas or in good sheltered conditions they may be continuous breeders. When mature the larvae are a little longer than the adults, densely pubescent and have a pair of rather short and curved urogomphi. They are voracious feeders and sometimes used by museums to strip remains from skeletons before presentation, they are also useful in forensics in establishing time of death.
This medium sized beetle, 7-9.5mm is very distinctive and usually unmistakeable due to its overall appearance; all dark with the basal half to third of the elytra covered in dense greyish or brownish pubescence, almost always with 3 dark spots arranged in a broad triangular pattern on each.