Carabus arvensis Herbst, 1784
This is a very widespread Palaearctic species; absent from North Africa but occurring throughout Europe and eastward through Asia Minor, Ukraine and Russia to Siberia and Japan. There are at least 10 subspecies of more restricted range, the nominate form occurs throughout Europe and extends north above the Arctic Circle while the UK population is represented by subspecies sylvaticus Dejean, 1826 which otherwise has a restricted central European distribution, extending south to Switzerland. The UK distribution includes most of the mainland, the Isle of Wight, Anglesey, Man Orkney and the Western Isles although it is very local and scarce in the southeast. Throughout much of the European range it is local and generally rare and there has been a recent and widespread decline, more generally it is a species of sparsely vegetated areas and blanket bogs in mountain habitats but in the north it is mostly a lowland heath and conifer forest species while further south it is more typical of woodland margins. There has also been a decline in the UK, both in abundance and range, and it is now absent from many of its former sites, especially in the south, here it is typically an insect of dry Calluna heathland and moorland, as it was in many southern Baltic areas where heathland is now very reduced or destroyed completely and the beetles now occur in pine forests on sandy soils. Adults are flightless, they disperse by walking and so are seriously affected by habitat destruction or fragmentation, they are long-lived and active from early spring until late in the year although older adults become dormant in the summer and remain inactive until the following spring, they are diurnal as well as nocturnal predators and hunt other insects etc. on the ground. Abundance peaks in May and June when mating occurs, eggs are laid in the soil and larvae develop through the summer producing new adults in August and September, these will become active through the late summer and autumn and overwinter among moss or in tree stumps etc.
Carabus arvensis ♀
Carabus arvensis ♂
Although the colour is very variable this species is distinctive among our fauna due to its small size and elytral sculpture. 16-20mm. Dorsal surface usually shiny metallic bronze or coppery but varies from black to green, purple or blue. Head slightly transverse with prominent convex eyes, surface roughly sculptured and finely punctured, antennae long and slender, palps only weakly broadened apically, penultimate segment of labial palps with 2 long setae on the inner surface. Pronotum transverse and evenly curved laterally to rounded and weakly produced posterior angles, only slightly convex anteriorly and flattened across the disc, surface roughly sculptured; punctures large and sparse behind the anterior margin becoming dense and confluent towards the base. Elytra with rather narrow and sloping shoulders and evenly curved to the apex; not, or only very weakly, sinuate before the apical angle. Surface sculpture consists of 3 longitudinal rows of large elongate tubercles, each separated by 2 or 3 weaker ridges which are often interrupted and flattened; at X20 the whole arrangement is roughened and nowhere smooth, in contrast to that in the larger C. monilis Fab., the only species with which this might be confused.