Pterostichus adstrictus Eschscholtz, 1823
This Boreo-arctic species has a circumpolar distribution; it is locally common across northern Siberia east to Kamchatka, Japan and North Korea, and across North America from Labrador to Alaska and south along the mountainous west, in Europe it is present in the UK and throughout Norway and Sweden and it is patchily distributed in Finland, it occurs on Faroe and is present in near-coastal lowland areas in Iceland. The species is otherwise almost absent from Europe but relict post-glacial populations surviving in the Swiss and Austrian Alps represent the southern limit of the distribution. In the UK it locally common in Wales and Northern England and rather less so throughout Scotland, including Orkney and Shetland, and across northern and eastern Ireland. Through most of the northern coniferous forest belt it is generally common and in suitable habitats from lowlands to above 2200 m, in Northern Europe and North America it is often the most common carabid. The usual habitats are upland heaths and moors where it occurs under rocks and debris in a range of both dry and wet situations, often in open fields or grassland with patches of exposed soil or gravel etc., but also among deep litter in open woodland or extensive forests. Adults are present year-round; they are active from April until September or October and peak in abundance during June and July. Reproduction occurs early in the season and larvae develop through the summer, new-generation adults appear from August and these will go on to overwinter but it is not known whether the larvae develop over a single summer. Both adults and larvae are predatory and hunt for other insects etc. under stones or among scree or patchy vegetation. Adults are active both by day and at night, they are fully-winged but details of their dispersion are not known. Sampling is usually by hand searching or pitfall trapping, the beetles usually occur in numbers and often alongside other medium-sized carabids.
Pterostichus adstrictus 1
Pterostichus adstrictus 2
10-13 mm. A rather broad and flattened species, glabrous with the body and appendages shiny black or, in females, with the elytra strongly microsculptured and often with a dark bronze lustre. Head with two setiferous punctures beside each eye and robust and sharp mandibles, antennae filiform with the basal segment as long as the third segment. Pronotum broadest in front of the middle and narrowed to obtuse anterior angles and slightly protruding posterior angles, lateral border wide and of equal width before it widens towards the base, surface longitudinally impressed medially, often more strongly so towards the base, and with linear and deep basal fovea which may be punctured or wrinkled, basal margin almost straight. Elytra parallel-sided or only slightly dilated from rounded shoulders to a subapical constriction, basal border complete, striae, including a scutellary striole, narrow, often rather fine, and unpunctured, interstices flat, the third with four to six foveate punctures (a good field character). Epipleura crossed before the apex. Legs long and robust. All tibiae with paired apical spurs distinctly shorter than the first tarsomere, front tibiae strongly widened from the internal notch. Tarsi with 5 simple segments (without dorsal furrows), the front tarsi only slightly wider in males, terminal segment without ventral setae.
Superficially similar to P. oblongopunctatus but with the legs black, or at least very dark, throughout, the basal antennomere is slightly longer, the pronotal border is wider and the base straighter.