Attagenus pellio (Linnaeus, 1758)
Two-Spotted Carpet Beetle
Native and widespread in the western Palaearctic region this species is now cosmopolitan having been spread from early times with the worldwide trade in food products e.g. it was first recorded in America in 1827. In Europe it is commonest in southern regions but extends sporadically to the UK and the far north of Scandinavia; here it is locally common in the southeast of England, East Anglia, the midlands and Wales and is only occasionally recorded elsewhere. Although occurring in the wild it is also commonly a pest of various household items and foodstuffs; larvae damage wool, leather, carpets, silk and all kinds of stored plant products as well as dried and smoked meats and fish, and they will consume the remains of other pest species within these materials. In the wild they develop among detritus in avian nests and so commonly enter roofs and sheds where nests occur, there is a single generation each year in warmer temperate climates with larvae developing in the spring and summer and adults overwintering but in more northern latitudes larvae can overwinter and the life-cycle may extend over two or three years. Adults disperse by flight in the spring and at this time occur on flowers and blossom where they feed on pollen and nectar, they seek out nests in old trees etc. and so commonly enter lofts and houses where they may be seen on walls or ceilings in the evening. Adults mate in the spring and if females encounter food in dark and undisturbed places they will lay a number of eggs directly on the surface and then move on in search of more host material. Hatching depends on temperature, at 18 Celsius they take about three weeks whereas at 30 Celsius larvae emerge within six days, larvae develop slowly; at 25-30 Celsius they take between 65 and 185 days to become fully grown, depending on the food source; in the wild they have been observed consuming feathers and dead insects but they also develop entirely on droppings in commercial poultry houses. Fully grown larvae are about 6mm long, have a banded appearance typical of the family and a tuft of long setae on the last abdominal segment, they avoid light and when disturbed remain in
a slightly curved condition and motionless for long periods. Pupation occurs among debris or within the host material and adults eclose within a week or two but remain within the pupal case for up to three weeks before emerging and flying to flowers to feed and mature. Due mostly to improvements in hygiene, food storage and building design the species is less frequently encountered than formerly but as most infestations are caused by adults from wild populations entering buildings they are still frequently recorded and likely to remain so.
Adults are easily identified by the size and small white spots on the elytra. 3.5-6.0mm. Elongate-oval and continuous in outline, entirely shiny dark brown to black with the tarsi and the base of the antennae pale and patches of pale setae to the pronotum and elytra. Head, pronotum and elytra with short, semi-erect dark pubescence. Head evenly convex and finely punctured, with large convex eyes and slender 11-segmented antennae. Antennal club 3-segmented and dimorphic; the terminal segment longer than the penultimate segment in the male but slightly shorter than the penultimate segment in the female. Pronotum transverse; broadest across the base and narrowed to a rounded anterior margin, basal margin strongly bisinuate and posterior angles sharply acute, surface finely punctured and microsculptured and usually with pale setae laterally and in front of the scutellum. Elytra smoothly rounded and completely covering the abdomen, finely and randomly punctured and lacking striae. Legs long and slender, usually dark with pale tarsi.
The variety pilosissimus Roubal, 1932 differs in having yellowish pubescence to the pronotum and elytra, it is known from only a few Italian specimens and is now considered as no more than a rare colour variety.