Carabus intricatus Linnaeus, 1761
Blue Ground Beetle
This species has a rather restricted European distribution; the nominate subspecies is widespread, from France east to Asia Minor, western Russia and Ukraine and north to Denmark, Sweden and the UK and appears to be generally local and rare, while 3 more subspecies are very local; 2 are restricted to Italy and one to Greece. The species is listed as near-threatened on the IUCN Red List and as threatened in certain areas such as the Netherlands, Luxembourg, Belgium and Denmark. It is extinct in Latvia and has undergone a Europe-wide decline in recent decades. In the UK it has always been a very local and rare species and has variously been considered as extinct, in 1994 it was established in only 2 sites, both on the margins of Dartmoor, but has since been recorded from a further Dartmoor location, 3 sites on the margins of Bodmin Moor and a coastal site in South Wales. Adults are long-lived, 2 or 3 years, and occur year-round; they overwinter beneath deep moss on trunks and logs or within dead wood and are active over a long season from early spring to late autumn, and typically occur in established damp and humid beech and oak woodland with deep leaf-litter, plenty of mossy areas and little vegetation. They are nocturnal predators, feeding on worms and other insects but seem to have a preference for certain slugs e.g. Lehmannia marginata (Muller, 1774) and Limax cinereoniger Wolf, 1803, following slime trails across the ground or up tree trunks to find their prey, and by day they rest under debris or loose bark on dead trees. Eggs are laid in the spring and larvae develop through the summer, they are fully-grown by late summer and pupation occurs in the autumn although it is sometimes thought the larvae may take 2 years to complete their development. Adults are flightless and disperse by walking, as with many nocturnal carabids the best way to find them is by searching trunks and the surrounding area by torchlight.
At 25-35mm this is our largest member of the genus. It is very distinctive and unique among our species in having the forebody long and narrow compared with the elytra, rather like Cychrus. Entire body metallic blue, appendages black, head and pronotum flat, elytra convex. Head quadrate with forwardly pointing curved mandibles and long, thin antennae, vertex and frons strongly sculptured and clypeus emarginate anteriorly. Apical segment of all palps triangular, more widely so in the male, penultimate segment of labial palpi with at least 3 setae on the inner margin. Pronotum quadrate, broadest in front of the middle and sinuate in the basal half, more strongly so in the male, surface strongly rugose towards the margins, more weakly and transversely rugose on the disc. Elytra long-oval with sloping shoulders and sinuate before the apex, more strongly so in the female, sculpture consists of multiple interrupted longitudinal carinae, usually with a few larger ones separated by a number of weaker ones. Legs slender and very long, more so than in our other Carabus species, basal pro-tarsal segments dilated in the male.