Carabus granulatus Linnaeus, 1758
This is a generally common Holarctic species; it occurs throughout Europe north to mid-Scandinavian latitudes and east to the Pacific and Japan, and following introductions from 1890, is now widespread across the United States and Canadian border regions; in the UK it is locally common throughout including all the islands except Orkney and Shetland. It is typically a species of wetland margins but may also occur in permanently damp and shaded woodland etc., in Ireland it is the most common member of the genus and occurs also in coastal regions and occasionally in gardens, and across much of its range it occurs in upland and mountain regions among peat and blanket bogs etc. Adults occur year-round; they overwinter under bark, among litter or under logs etc. and become active in March or April although they may also become active during mild winter spells, they are nocturnal predators feeding on a variety of insects and worms etc. but they also, or even predominantly, predate snails; they have been observed inspecting numbers of snails before deciding upon a suitable prey item and it is thought they may be adapted to feed primarily on dextral snails, those that coil to the right and which comprise more than 80% of European specimens, and as most of the beetles have the left mandible overlaying the right this may be an adaptation to hunting dextral snails, sinistral snails being largely immune to attack. Unlike Phosphuga and Cychrus, C. granulatus does not attack the snail with digestive enzymes but simply reaches into the shell with its mandibles, butchers it extensively and then pulls it from the shell. Mating occurs from April and oviposition begins a little later, individual eggs are laid in burrows a few cm deep which are then filled with soil and they hatch within a week or two. The nocturnal and predatory larvae develop through the summer, they pass through 3 instars and are fully grown within 40 to 60 days, pupation occurs from late summer and new-generation adults appear in the autumn. Overwintered adults may reproduce in the spring but some, and perhaps a majority, do not and will overwinter a second time before doing so. In the UK the species has reduced wings and is flightless but in central Europe fully winged specimens have been observed to fly. Adults may be found by searching under debris or among marginal vegetation, although we have found them under logs some distance from water, and they will remain in damp woodland through the summer, but pitfall trapping is undoubtedly the easiest way to record them.
This is the type species of the genus and at least 9 subspecies occur throughout the range; the nominate subspecies occurs on the mainland whereas in Ireland it is represented by ssp. hibernicus Lindroth, 1956 which has weaker elytral keels but is more strongly microsculptured, intermediate forms occur in the west of England. 16-23mm. A narrow and elongate species; usually entirely dark metallic bronze but greenish or bluish specimens occur, with dark appendages although pale-legged forms occur on the continent. Head long and narrow with robust projecting mandibles, prominent and convex eyes and long palps and antennae. Pronotum transverse with variously produced posterior angles, lateral margins raised and posteriorly sinuate, surface roughly sculptured, with more-or-less well-defined basal fovea. Elytra evenly rounded from sloping shoulders, each with a single row of long tubercles between 3 raised carinae, the sutural abbreviated about the middle, the outer 2 continued at least into the apical third. Legs long and robust; middle and hind legs slender, fore-legs broader, all tibiae with 2 strong apical spurs, fore-tibiae without an internal antennal-cleaning notch. Basal pro-tarsal segments dilated in the male.