Rugilus erichsonii (Fauvel, 1867)
This is a mostly Western Palaearctic species, it occurs throughout Europe and the Near East and extends into parts of Western Russia, to the north it extends to the UK, Denmark and into central provinces of Fennoscandia, it is generally common in western and central areas but becomes less so going east. In the UK it is locally common throughout England and Wales and very local in parts of South West Scotland and Northern Ireland. Adults are active throughout the year although they are less frequently seen during August and December; they peak in abundance from May until July and again in September or October, suggesting spring and summer breeding. Typical of the group both adults and larvae are predatory but beyond this little is known of the habits or life cycle. The species is generally associated with decaying vegetation in wetlands and permanently damp grassland etc, but it also occurs more generally e.g. on agricultural borders or in damp woodland and it often frequents compost and decaying straw etc in ruderal situations. Adults may be sampled by sieving suitable material, they often occur in flood refuse and among winter extraction samples and occasionally appear in flight-interception traps.
4.0-4.5 mm. Very typical of the genus, but here the elytra are broader than the pronotum but narrower than the head. Body entirely dull black to dark brown, elytra reddish inside the outer apical angles, sometimes this may continue narrowly along the apical margin, mandibles and appendages entirely reddish-brown. Head quadrate or slightly transverse (measured to the anterior clypeal margin) and broadest across large eyes that occupy at least half the lateral margin, temples rounded from the eyes to a straight basal margin, surface densely and finely punctured but for a smooth median patch. Pronotum elongate, almost straight laterally and strongly narrowed to a rounded apical margin and straight basal margin, surface closely punctured but for a median smooth strip which may be weakly impressed towards the base. Elytra quadrate, weakly curved from rounded shoulders to separately incurved apical margins, surface rather shiny and with punctures only about half as strong as those on the pronotum and separated by more than their own diameter, without striae but impressed alongside the suture. Abdomen long and dilated about the middle, basal tergites strongly bordered, all tergites finely punctured but for much stronger punctures in the transverse grooves of the basal tergites. Seventh tergite in males with a shallow arcuate excision on the apical margin.