Leptacinus batychrus (Gyllenhal, 1827)
This Palaearctic-wide species occurs throughout Europe to the far north of Fennoscandia, it is present on many of the Mediterranean and Atlantic islands, and is widespread across North Africa, it is also established in North America, where it is thought to have been introduced during the 19th Century, and there are records from Southern Australia. The species is locally common from lowlands to lower mountain altitudes in Central and Northern Europe, but otherwise much more local and rarely recorded although there are exceptions e.g. it can be very common on some of the Mediterranean islands. In the UK it is widespread though very local in England and Wales, and generally scarce further north to the Scottish Highlands and Western Isles. Adults are associated with decaying plant material; often in dung or dung/straw mixtures, and often in synanthropic or other disturbed situations, more generally but much less frequently among compost in gardens and parks etc or in well-decayed leaf litter etc, and they may occasionally be associated with small mammal burrows. Adults are present year-round; they overwinter among host material or in soil and are active from March until November, peaking in abundance during spring and early summer, and again in August or September. Little is known of the biology but both adults and larvae are predatory, and breeding probably occurs in spring and early summer. Adults are easily sampled by sieving compost or working through dung and straw etc., they sometimes fly on warm evenings and may occasionally be swept from vegetation in disturbed areas.
5-7 mm. Elongate and parallel-sided, shiny dark brown to black with the elytra becoming pale yellowish in the apical half to two-thirds, palps brown, antennae brown but usually becoming darker apically, legs pale brown. Head elongate, with small and flat eyes and long, slightly diverging temples to a curved or almost straight basal margin, surface moderately-strongly but not densely punctured, anteriorly with four furrows; the outer pair, starting from the anterior margin of the eyes, longer and extending toward the middle of the head. Terminal maxillary palpomere narrow and pointed; at most only half as wide as the previous segment. Antennae inserted dorsally inside the outer margins of the mandibles; 11-segmented; basal segment elongate and broad, segments 4-10 transverse. Pronotum elongate, broadest across obtuse anterior angles and narrowed to a rounded basal margin, lateral border continued onto the apical margin, not reflexed anteriorly, surface with two longitudinal series of 11-13 punctures. Microsculpture of head and pronotum variable but wavy transverse lines are always present, at least in places, on the basal half of the pronotum. Elytra weakly dilated from rounded shoulders to separately-curved apical margins, sutural margins overlapping, surface with fine semi-erect pubescence and strong punctures arranged mostly in loose longitudinal lines. Abdomen long and usually a little dilated about the middle, tergites sparsely and finely punctured and with transverse microsculpture. Eighth sternite in males with a shallow V-shaped emargination and a fringe of short pale setae. Legs short and robust. Femora broad and unarmed, tibiae only weakly expanded from the base, all with spines along the outer margin; front tibiae not excavate at the base, each with a long spine on the internal apical angle. Tarsi 5-segmented; the elongate terminal segment longer than the others. Distinctive among our species by the combination of size, at least 11 punctures in the pronotal series, yellowish elytral apices and long, almost parallel-sided head. Aedeagus distinctive; large and broadly rounded with small and curved parameres.