Carabus auratus Linnaeus, 1761
Golden Ground Beetle
This species has a restricted western and central European distribution extending east from Spain to central Poland and Romania although it has been spreading east in recent decades and so the range may increase, it is locally common in the Netherlands but is generally absent from the north and most of the Mediterranean regions though following introductions has become established in Turkey, southern Scandinavia and the UK. It was also introduced into the United States in the 1940s to help control gypsy moth and brown-tail moth and has become established and widespread; it was first recorded in Canada in 2013. Throughout Europe they occur from lowlands up to 2500m. It has long been recorded as an occasional vagrant in the UK and there are a couple of (introduced) populations established in Berkshire and Kent. Adults occur year-round and are active from May until August, they are sun-loving and inhabit open situations such as grassland and agricultural borders, often on clay soils, avoiding wooded areas and other shaded situations and they often occur in parks and gardens. Unlike most members of the genus they rest in the soil or among litter during the night and are diurnal predators, hunting worms, molluscs and other insects and their larvae among vegetation; they often take prey much larger than themselves but also regularly consume dead slugs and snails and climb trees in search of prey. Adults live for 2 years, they overwinter in the soil and breed early in the year, mating occurs mostly in the spring and females lay up to 50 eggs, singly or in small batches, in the ground. Larvae develop through the spring and summer, they predate worms and other insects on the ground during the morning and evening and develop rapidly; they pass through 3 instars and pupate in the soil from late summer, new generation adults appear in the autumn but are seldom active, generally moving under rocks or into the soil to overwinter.
This large and brightly coloured ground beetle is quite distinctive among the UK fauna and might only be confused with the smaller (13-18mm) Carabus nitens L. 20-27mm. Entirely bright metallic green to coppery-green with contrasting metallic red or coppery margins to the pronotum and elytra and pale legs. Antennae dark with 4 pale basal segments. Pronotum transverse and widest in front of the middle, lateral margins strongly bordered, surface transversely winkled but otherwise smooth and shiny on the disc becoming strongly rugose towards the margins. Elytra each with 3 strongly raised longitudinal keels which are smooth compared to the finely rugose adjacent cuticle but similarly coloured, in C. nitens the raised keels are black and contrasting with the green and strongly rugose intervals.