Silis ruficollis (Fabricius, 1775)
This species has a rather patchy European distribution extending from France and northern Italy to Ukraine but it is absent from the Balkans and south of the Black Sea, to the north it extends to the UK, Denmark and into southern provinces of Fennoscandia but has not been recorded from many of the northern Baltic countries such as Latvia and Estonia, and to the east it extends through Russia as far as the Caspian Sea, through most of this range it is locally common though restricted by habitat and in certain northern areas e.g. Denmark, it seems to be increasing its range. In the UK it is locally common in the south and east of England north to the Wash and around the Severn estuary and coastal south Wales, beyond this there are a few scattered records from the West Country and further north as far as Leeds; it was for a long time considered to be rare in the UK and was designated as nationally notable but there has been an increase in both range and abundance over recent decades. Adults occur over a short season from May until July although in the UK they are rarely seen before early June; they occur in a range of wetland and permanently damp situations; floodplains, bogs, fens and river and pond margins etc. Adults are diurnal and may be found among herbaceous vegetation and on trees and shrubs in suitable situations, they are predaceous but during warm spells they visit umbels and other flowers where they have been observed feeding on pollen, they are fly readily and in warm weather may occasionally occur far from suitable habitats. Little is known of the species biology but larvae are typical of the family, they are predaceous, terrestrial and occur in much the4 same habitats as the adults, they develop through the summer and probably overwinter in the soil or among litter etc and pupate in the spring. Sweeping vegetation in suitable habitats is the best way to sample the species; in south Hertfordshire, where it is generally common, we often see them in flight over wetland vegetation during warm weather.
Adults may casually be mistaken for one of our smaller dark species of Cantharis but the overall colour, robust black antennae and the form of the pronotum will soon become familiar in the field. 6-7.5mm. Vertex of head black, clypeus and frons pale, pronotum pale, elytra dark grey to black, including the epipleura, antennae entirely black, legs black with the tibiae substantially pale. The pronotum is transverse, broadest in front of the middle rounded anteriorly to a more or less straight anterior margin, the lateral margin is strongly sinuate before protruding posterior angles and the basal margin is sinuate laterally, produced backwards and incised medially, the surface is irregular and mostly smooth but the disc and the basal margin are strongly punctured and there is a sinuate ridge extending from each posterior angle laterally to about the middle, the sexes may be distinguished by the form of the lateral margin; in the male it is more strongly indented before posterior angles that are rounded or truncate, in the female it is less strongly indented and the posterior angle is sharply acute. Elytra roughly sculptured and densely punctured throughout, without striae but usually with three variously-developed longitudinal ridges, shoulders rounded and slightly narrower than the base of the pronotum, apical margins separately rounded.