Elaphrus cupreus Duftschmid, 1812
This widespread and generally common Palaearctic native occurs from lowland to mountain altitudes throughout Europe from the northern Mediterranean to Scandinavia and the UK; here it is common in wetland situations throughout including the Isle of Weight, Anglesey, Isle of Man, Western Scottish Islands and Orkney. Typical habitats include open or vegetated margins of both standing and moving waters; rivers, fens, marshland and sphagnum bogs etc., they are likely to occur in almost any undisturbed situation and new habitats are often quickly colonized as they disperse by flight in the spring. Compared with the other common species, E. riparius (Linnaeus, 1758), they prefer more shady and vegetated situations but this is by no means general and the two often occur together. Adults occur year-round and are generally active from April to September, they live for about a year, overwinter once and breed in the spring, and usually occur in colonies of numerous individuals which may extend for many metres along the water edge and away from the water for as far as the ground is permanently damp. They are diurnal and active in bright sun where they may be seen running across bare areas of soil, they move rapidly and are cryptic, especially among vegetation, and are difficult to follow because when disturbed they scatter among plants or leaf-litter, under debris or into crack in the soil, and if near the water edge will run across the water for several metres to escape a threat. Mating occurs in the spring when pairs may be seen on the substrate and oviposition occurs soon after; eggs are laid directly into wet soil or among waterside moss or litter depending on the nature of the habitat but those laid into waterlogged soil are known to have a high rate of survival. Larvae emerge within a few days and develop quickly, they are nocturnal predators of other insects and larvae as well as worms and other small animals active on the surface, and when fully-grown they pupate in the soil or litter etc. among vegetation. The entire cycle from egg to adult takes about 38 days. New generation adults appear in the summer and unlike many other carabids do not aestivate, they remain active and are mature within one or two months. Adults are diurnal predators of other small animals and the males are generally
more active the females, they often live within specific areas, spending much time in a ‘den’ and are generally territorial towards other predatory beetles etc. but nonetheless they will usually be found along with others e.g. species of Agonum or Bembidion; they will threaten other predators or escape by running rapidly to the den, taking flight or remaining motionless, and when alarmed will stridulate. They remain active into October or November, depending upon the season, when they burrow down between five and ten centimetres into wet substrate to overwinter.
8.0-9.5mm, larger and darker than the common E. riparius; usually appearing somewhat violet in sunlight rather than green as in that species. Both will soon become obvious in the field. Dorsal aspect entirely dark brown to black, often with a purple or green reflection. Antennae dark with the first few segments metallic, legs dark metallic; the tarsi and apices of the tibiae blue, the tibiae otherwise pale. Width of the head measured across the huge convex eyes a little greater than the pronotum, mandibles and labrum prominent. Pronotum quadrate or nearly so and heavily sculptured; with a deep longitudinal median furrow and a pair of distinct fovea anterior to the middle, smoothly rounded laterally and strongly sinuate before shape and protruding posterior angles. Prosternum glabrous although there may be a few long hairs on the process, a condition also seen in E. uliginosus Fabricius, 1792. Each elytron with 4 rows of strongly punctured purple depressions, the inner two rows with three or four raised, flat and smooth ‘mirrors’. Elytra much wider than the foreparts, with prominent shoulders, gradually widened towards the middle and smoothly and continuously rounded apically. Male with basal pro-tarsal segments dilated.