Sepedophilus marshami (Stephens, 1832)
This very widespread species is locally common from lowland to low mountain altitudes throughout Europe including the Azores and northwest Africa; it extends north to the Arctic Circle in Scandinavia and east through Russia to Korea. It was discovered in the Nearctic region in Quebec in 1959 and is now widespread in Canada and the United States. In the UK it is generally common across England and Wales north to South Yorkshire, further north it is more local and mostly eastern although it occurs on Man, and there are a few records from the east of Scotland. It is a widely eurytopic species and adults occur in a range of habitats; most commonly around decaying logs or stumps but also among bracket fungi, leaf-litter, moss, old hay and straw, in tussocks and even old dry dung and it has been found in the nests of a range of ant species including Formica rufa Linnaeus, 1761, Lasius brunneus (Latreille, 1798), L. fuliginosus (Latreille, 1798), L. niger (Linnaeus, 1758) and Myrmica ruginodis Nylander, 1846. In general they prefer shaded and damp habitats but they also occur among damp decaying vegetation in exposed marginal habitats. Adults will be encountered when searching under logs or among decaying timber and during the warmest weather they may be active on the surface but they are mostly nocturnal, here they are active on the surface of wood and fungi etc. and are readily observed by torchlight although they are easily startled, run extremely rapidly and vanish into crevices or among litter very quickly. Adults occur year-round and are most common in the autumn when they are easily sampled by sieving or pitfall trapping, during the winter they regularly occur in suitable extraction samples or among tussocks and they occur in ant nests through the autumn and winter.
This species will soon become familiar in the field, the very elongate 'fusiform' shape (which usually contracts in set specimens), contrasting head, pronotum and elytral colouration and overall silky appearance produced by the rather dense pubescence is distinctive.
4.0-5.5mm. Head shiny black with the labrum and mouthparts testaceous, finely punctured and pubescent, eyes reniform and weakly convex. Antennae long and slender, inserted laterally in front of the eyes and pale with the middle segments darkened; segments 1-4 elongate, 5 -8 less so and 9 and 10 more or less quadrate, terminal segment asymmetric. Pronotum convex and distinctly wider than the elytra; broadest behind the middle and evenly rounded to obtuse hind angles, basal margin evenly curved; not sinuate towards the posterior angles, shiny black with the lateral margins pale. Surface finely punctured and pubescent and with very fine transverse microsculpture which is just visible at X40. Elytra quadrate or slightly transverse, broadest near the base and narrowed to rounded posterior angles, surface finely punctured and pubescent; lacking outstanding long setae. Colour when mature distinctive chestnut-brown with darker areas around the scutellum and shoulders. Abdomen long and evenly tapering to the apex although it is often contracted in set specimens, lateral margins weakly developed and present only on the basal segments. Finely punctured and pubescent, segments dark with paler apical margins, apical segments with long dark setae. Legs long, slender and entirely testaceous. Tarsi 5-segmented, basal pro-tarsal segments dilated, more strongly so in the male.