Poecilus cupreus (Linnaeus, 1758)
This is one of the most widespread and generally common member of the genus; it is present throughout Europe except for the far north of Fennoscandia and extends through Asia Minor and Russia to eastern Siberia; the nominate subspecies is present throughout most of this range, including the UK, but several others are more local e.g. P. cupreus dimmiki (Lutshnik, 1912) from Ukraine and southwest Russia or P. cupreus erythropus (Dejean, 1828) from southwest Russia and the eastern Palaearctic region. Here it is common and often abundant throughout England and Wales, including all the islands, though more sparse in the north and confined to the south and west in Scotland where it seems to have declined over recent decades. Adults occur year-round; occasionally in woodland but mostly in open and dry habitats exposed to the sun, usually grassland and pasture but often agricultural land, parkland and even domestic gardens although in central and northern Europe they often prefer permanently damp pasture and even wetland margins with plenty of tall vegetation. They are active on the warmest days in the spring and early summer when they disperse by flight in bright sunshine but they are generally crepuscular and nocturnal and may be found by torchlight on pathways and among vegetation. Reproduction occurs from April until July and larvae develop through the spring and summer, the first new-generation adults appear in August and these will go on to overwinter and breed the following spring and at least some will survive and go on to overwinter and breed for a second time. Larvae are terrestrial predators, feeding upon eggs and larvae of other small arthropods while adults are omnivorous; for most of their active season they predate other insects as well as worms and slugs and will feed on crushed insects on pathways but they also consume grass seeds etc, especially in the spring when they have been known to damage beet seedlings.
Adults are large, 11-13mm and bright metallic green, coppery, bluish-red or purple with black appendages but for the two basal antennal segments which are pale red; in the rare variety affinis Sturm the body is black and the appendages pale. Among our UK carabids it may be distinguished by the combination of size and colour, two setiferous punctures beside each eye and the two or three basal antennomeres which have a fine dorsal longitudinal keel, the only confusion should be with the our other members of the genus, see below. Head with the vertex finely but distinctly punctured (easiest to appreciate behind the level of the eyes), otherwise smooth to a distinct but often faint frontoclypeal suture, palps black with the tips narrowly yellow, antennae black with two basal segments pale brown to red, segments 1-3 glabrous and finely keeled above. Pronotum transverse and widest about the middle, lateral margins evenly curved to rounded anterior angles and slightly protruding posterior angles, basal margin weakly sinuate, surface widely explanate behind the middle and extensively punctured across the base, basal fovea well-impressed; the outer short and oblique, the inner longer and straighter. Elytra broadly oval and rather flattened, with unpunctured or only finely punctured striae (mostly towards the base), including an abbreviated scutellary stria, interstices weakly convex, the third with two setiferous punctures close to the second stria, epipleurs crossed subapically. Hind tibiae with at least eight fine setae along the inner margin; the first of which being as long as the others, basal segments of hind tarsi with a deep external furrow. Males are shinier than females and have the basal segments of the front tarsi strongly dilated.
Head unpunctured behind the eyes
Hind tibiae with at most 8 fine setae along the inner margin
Elytral striae more extensively punctured