Pterostichus aterrimus (Herbst, 1784)
Widespread but very local and rare throughout lowland Europe and North Africa, reaching north into Ireland, Denmark and the Baltic countries to about 62°N in Fennoscandia, also present in the Azores and Madeira and known from Western Siberia the nominate subspecies occurs throughout this range while ssp. nigerrimus (Dejean, 1828) occurs in Spain, Portugal, France and North Africa, and ssp. ausonicus (Bucciarelli & Perissinotto, 1959) is endemic to Italy. In the UK it was formerly known from East Anglia and Hampshire but the species has not been recorded since 1973 and both colonies are believed to have died out, it is known from about a dozen sites in Ireland, mostly in the north, although beyond this the status is unknown. Typical habitats are densely-vegetated wetlands, often on acidic substrates with oligotrophic conditions; peat bogs, marshes and reed beds, sometimes in areas disturbed by cattle or people, in Ireland it occurs only the early stages of raised bog formation, and in the Azores it is known from salt marshes. Adults are present year-round they are active from March until July or August and peak in abundance during the spring later in Northern Europe). Reproduction occurs in the spring and new-generation adults appear in the autumn, they are mostly nocturnal and are believed to disperse by flight; most specimens have fully-developed wings and flight muscles and flight has been observed in Northern Europe. Adults should be sought among areas of dense grasses, sedges and reeds or among waterlogged moss etc. on wet soil beside standing or slow-moving water, and specimens should be examined carefully as other interesting carabids e.g. Carabus clatratus Linnaeus, 1761, Pterostichus rhaeticus Heer, 1837, P. anthracinus (Illiger, 1798) and Agonum ericeti (Panzer, 180) occur in much the same situation. Pitfall trapping is an ideal way to record the species but this can be very destructive and should be done only when the traps can be inspected frequently.
13-15 mm. Robust and rather parallel-sided species with a large head and rounded pronotum, glabrous and entirely shiny black. Head with weakly-convex eyes and long temples and cheeks, vertex smoothly convex, inner margin of each eye with two setiferous punctures, clypeus with two curved furrows, Pronotum transverse, curved laterally to slightly-projecting anterior angles and widely-rounded posterior angles, explanate margin narrow throughout, basal furrows deep and rather sharply delimited externally, Elytra rather parallel-sided from rounded shoulders to a continuous apical margin, inner striae well-impressed and finely punctured, outer striae weak, interstices flat or weakly convex, the third with three or four deep and foveate punctures, epipleura crossed before the apex, Legs long and robust; front tibiae strongly broadened beyond the antennal-cleaning notches, all tibiae with strong apical spurs. First meta-tarsomere with a fine external keel or furrow, last segment of all tarsi without ventral setae. Easily distinguished among our species by the rounded posterior pronotal angles, foveate elytral punctures and lack of setae beneath the claw-bearing tarsomeres.