Calosoma sycophanta (Linnaeus, 1758)
This is the most widespread and generally common member of the genus; it occurs in lowland areas across northwest Africa and throughout Europe from the Mediterranean north to Germany and east through Asia Minor and Siberia to China, and further north it is occasionally recorded from Scandinavia and the UK. Following intentional introductions to control gypsy moths it has now become established in several areas in the eastern United States. In many European countries, especially in southern areas, it remains generally abundant but in central areas e.g. Germany, has suffered a recent and abrupt decline thought to be caused by forestry management. It is probably native to the UK and has been recorded fairly frequently since the 19th century, many sightings have been near-coastal from the southeast and so attributed to occasional immigration but inland records may relate to specimens introduced by other means and the only verified breeding population was recorded from West Suffolk. Adults generally occur during the warmer months and, at least on the continent, large populations may occur in line with those of the host caterpillars which include various species of tussock moths (Lymantriidae) and processionary moths (Thaumetopoeidae). The typical habitat is deciduous woodland and orchards etc although adults have also been recorded from grassland and conifer woods on the continent, they occur year-round but are mostly active during the spring and early summer, rarely after July, they are excellent fliers and regularly recorded from light, especially in the spring. Both adults and larvae feed on moth larvae and pupae and both are gregarious, they climb trees and actively stalk prey both by night and by day, they also hunt on the ground where they have a more diverse diet and females generally spend more time on the ground than males or larvae. Adults are long-lived, between 2 and 4 years, they overwinter in subterranean cells between 5 and 50cm deep and some individuals have been observed to remain dormant for almost 2 years, and emerge in the spring to feed before mating begins, this has been observed through the spring and into the early summer. Eggs are laid in soil or among litter and freshly emerged larvae feed for a while on the ground before ascending trees to hunt, they develop rapidly and may be fully grown within a
month, pupation occurs in a cell in the soil and adults emerge from mid-summer although late eclosing adults may remain within the cell to overwinter. Populations tend to increase in line with those of the prey and for this reason they are thought to be an important regulating factor and biocontrol agent for moth populations, each adult may consume several hundred larvae during it lifetime and each larvae up to 50 during its brief development.
This large and spectacular carabid might only be mistaken with our other UK member of the genus, C. inquisitor (Linnaeus, 1758), which is consistently smaller and lacks the brilliant metallic elytral colouration.
24-30mm. A broad and flat species with a narrow head, transverse pronotum and parallel-sided elytra, forebody metallic dark blue and strongly contrasting with the brilliant golden green or coppery elytra. Head slightly transverse when measured across the convex and prominent eyes, evenly convex and roughly sculptured with broad, forwardly produced mandibles and long palps truncate palps that are only weakly broadened apically. Pronotum strongly rounded and sinuate just before the produced posterior angles, margin widely explanate and strongly bordered to the base, surface rugose and quite strongly punctured, especially towards the base. Scutellum smooth, triangular and dark; coloured as the pronotum. Elytra with 15 finely punctured striae and weakly convex interstices, the fourth and eighth with several larger punctures that usually adjoin the adjacent outer stria. Legs robust and very long, male with dilated pro-tarsal segments.