Nitidula bipunctata (Linnaeus, 1758)
This locally common species has been recorded across the entire Palaearctic region and sporadically across the United States, including Alaska, and Canada, where it is thought to be native, having been first recorded in 1878 from high altitudes in an isolated range of the Rocky Mountains, it occurs throughout central and northern Europe from the Pyrenees, northern Italy and the north of the Balkan Peninsula to the UK, Iceland and above the Arctic Circle in Scandinavia. It is present across the Near East but absent from most of the Mediterranean and Atlantic Islands and North Africa. In the UK it is widespread though very local across Wales and England north to Nottingham and sporadic and scarce further north to the Scottish Highlands. Adults have been recorded throughout the year but are most often recorded from early spring until early summer, they are nocturnal and usually associated with dry carrion in all stages of decay, they have also been found among old and dry bones and are strongly attracted to fermenting sap at night, they fly well and might be expected at suitable host material in any fairly dry situation. On the continent they are occasionally found among stored dry and smoked meats, and there are records of large infestations in food warehouses, bakeries and food-processing plants. Adults have been recorded living for up to 15 months under artificial conditions and they are likely to be long-lived in the wild as they have been recorded through the winter. Mating occurs in the spring when adults assemble at suitable host material and females lay numerous eggs among dry organic matter where the larvae will develop. Larval development depends on the quality of the host material but is usually rapid; they pass through three instars in about two months and pupate in adjacent soil, this stage lasts for about two weeks and fresh adults will disperse and feed but they will not reproduce until the following year. Females are fecund and each will lay up to 200 eggs under artificial conditions, this is probably also the case in the wild as numerous larvae have been observed among dry host material; freshly-emerged larvae are tiny and creamy yellow with brown spots along the dorsal surface, but when fully-grown they are up to 8mm long and distinctive yellow with the head and abdominal apex brown, and when found they should be taken along with a sample of the host material as they are reputed to be easy to rear to adults. Sampling is otherwise best done by examining suitable material or by dry-carrion trapping although they also occur at flight-interception traps in the spring.
3.0-5.0mm. Adults are easily recognized by their distinctive colour, body entirely dark grey to black with the pronotal margins and a (usually)round spot on each elytron pale red or orange, legs pale brown, antennae variable; often entirely black but sometimes pale towards the base or the entire funiculus may be pale. Dorsal surface finely and densely punctured and finely pubescent throughout. Head with protruding convex eyes and short converging temples and cheeks, surface flat or slightly concave and without impressions or structure, the punctures become confluent anteriorly and the clypeus is usually transversely rugose. Antennae 11-segmented and inserted laterally behind the outer margin of the mandibles, basal segment large and curved internally, 2-5 elongate, 6 & 7 quadrate or nearly so, 8 transverse and 9-11 form a wide and compact club. Pronotum transverse, broadest in front of slightly obtuse posterior angles and narrowed to distinct anterior angles, anterior margin straight, posterior margin weakly sinuate, surface smoothly convex but variously impressed across the basal half, lateral margins raised and explanate throughout. Scutellum triangular and rounded apically, the surface finely punctured and pubescent. Elytral base only very slightly broader than the pronotal base, shoulders rounded and smoothly convex, lateral margins narrowly explanate and smoothly curved to separately-rounded apical margins, surface without striae or impressions. Terminal abdominal tergite fully exposed beyond the elytra, sometimes also the apical margin of the penultimate tergite. Legs short and robust, the femora only narrowly visible in normal settling. All tibiae smooth externally and gradually expanded to a truncate apex and all with well-developed spurs at the inner apical angle. Tarsi 5-segmented; three basal segments wide and strongly lobed, the fourth small and narrow and the fifth long and curved. Claws smooth and lacking a basal tooth.