Dryops luridus (Erichson, 1847)
This widespread and generally common species occurs throughout Europe from Portugal to Greece and north to Southern Scandinavia and the UK, it is present on most of the Mediterranean islands as well as the Azores and occurs from lowland to medium altitudes; on Sardinia it is recorded at 950m. Here it is common throughout the UK north to Shetland, including all the islands, and is generally our most common member of the family. Typical habitats are the margins of fresh and brackish water, both running and still, and it is tolerant of stagnant water and so should be expected from most wetland situations. Adults occur year-round, they are active from April or May, usually among marginal vegetation or substrate and often in numbers, and are readily swept from such situations through the summer. During the winter they will occasionally occur in extraction samples, among flood debris or marginal litter. Larvae develop within substrate out of the water, generally near marginal situations, feeding on organic matter among roots or litter, and pupation occurs in similar situations.
For certain determination the aedeagus will need to be examined and females are best identified by comparison and association.
Adults are medium-sized beetles, 3.7-4.3mm and entirely black or very dark brown with the antennae and tarsi variously lighter. The dorsal pubescence is double, consisting of quite long and semi-erect setae above dense, short and very fine recumbent hairs. Head strongly microsculptured; with coarse punctures at the base which become very fine anteriorly, and large, convex and pubescent eyes. Antennae 10-segmented; second segment greatly enlarged, tapering to an acute apex and with 3 distinct lengths of pubescence on the inner surface, terminal segment very small and difficult to see. Antennal insertions closer together than either to the inner margin of the adjacent eye. Pronotum transverse and at most only slightly narrower than the elytra, broadest in front of acute posterior angles and evenly curved to sharp anterior angles, sometimes with an obscure median longitudinal ridge towards the base. The sub-lateral grooves are almost straight in the
basal half then curve inwards beyond the middle, the cuticle between roughly sculptured and finely, often obscurely, punctured. Elytra elongate and parallel-sided or weakly dilated behind the middle, rather flat between convex and prominent shoulders but otherwise convex, the surface roughly sculptured and finely and randomly punctured, usually with distinct rows of punctures between the shoulders and the scutellum and distinct longitudinal depressions. Legs long and slender with proportionally short tarsi; the pro- and meso-tarsi shorter than the respective tibiae. Tarsi 5-5-5, without lobed segments; the terminal segment by far the longest. Claws paired and equal on all legs; long, smooth and sharply pointed.