Clivina fossor (Linnaeus, 1758)
This is the most widespread of the Western Palaearctic species; it is generally common throughout Europe from lowlands to boreal mountain altitudes, extending north to UK and the north of Fennoscandia, south to Egypt and east through Asia Minor and Russia to China and the Kamchatka peninsula, it is also widespread across the northern United states following introductions in the early twentieth century. Here it is locally common and often abundant throughout the UK including all the islands north to Shetland. Adults occur year-round and are active over a long season from late winter until late in the autumn, they breed in the spring and the new-generation appears from late summer, they are fully-winged and strong fliers and so may suddenly appear in well-worked habitats. The species is quite widely eurytopic; typically occurring under stones or debris in open and permanently damp situations, often in grassland on heavy, slow-draining soils or in marginal wetland situations, though they are not particularly riparian, they sometimes occur on beaches among tidal drift but otherwise usually not in sandy situations, they also occur on arable land, or among well-decayed leaf-litter below hedgerows or on damp woodland borders and are sometimes common around upland peat bogs etc. Adults generally remain underground by day but will occasionally be found by turning stones etc; by night they become active and may be seen roaming areas of open damp soil in search of prey, they are mostly active in the spring and early summer and rarely encountered in the autumn.
Measuring 6.0-6.8mm this is the largest member of the subfamily and likely to be confused only with C. collaris; it is readily separated from the larger species of Dyschirius by the more-or-less continuous series of setiferous punctures between the elytral humerus and apex. Body entirely unmetallic black or dark brown, often with the sutural interval or lateral margin paler, appendages pale to dark brown. Head elongate with large convex eyes and short, slightly diverging temples, vertex impressed beside the eyes and the frons with a central fovea, moderately strongly punctured around the base but otherwise finely and sparsely punctured throughout. Antennae inserted under a lateral extension of the clypeus, segments 1-3 elongate, 4-10 quadrate to slightly elongate. Pronotum quadrate or nearly so, with distinct anterior and posterior
angles, the posterior angles finely toothed, surface with a longitudinal impression diverging anteriorly to inside the front angles and with fine transverse wrinkles and very fine punctures. Lateral margins narrowly explanate, with a setiferous puncture inside each angle and another in the anterior third. Elytra elongate, about 3:2, with rounded shoulders and a continuously curved apical margin, each with eight punctured striae complete to the apex, the third with three or four larger setiferous punctures, and a continuously punctured lateral margin. Forelegs fossorial with expanded femora and broad, strongly toothed tibiae, middle and hind femora normally developed. Mid tibiae with numerous stiff setae along the external margin and a long spur at the inner apical angle. Hind tibiae with stiff setae towards the apex and a long apical spur. Tarsi 5-segmented, pro-tarsi not expanded in the male. Dimorphism is slight but the sexes may be determined by the arrangement of four fine setae along the apical margin of the terminal sternite; in the male the central pair is closer than either is to the outer pair whereas in the female they are equidistant.