Lebia chlorocephala (Hoffman, J., 1803)
This western Palaearctic species is one of the most common and widespread members of the genus; it is locally common and sometimes abundant in warmer southern regions of Europe, extending south to the Mediterranean coast of Spain, central Italy and the Balkans, but more local and generally scarce north to the UK and central Fennoscandia, and to the east it extends through Asia Minor, The Caucasus and Russia into the west of Siberia. In the UK it remains very local across southern England and Wales, although adults may occasionally occur in numbers, and more sporadic and rare further north to the Scottish Highlands. In the UK its typical habitat is open grassland with plenty of herbaceous vegetation, often on sandy soil or calcareous hillsides etc, but in Europe it is more eurytopic, occurring in forests, parks and domestic gardens as well as grassland and often on moist clay or peaty soils. Adults occur year-round; they overwinter among tussocks or under stones or debris and become active early in the year, they are mostly crepuscular but may also be active in warm weather when they roam the soil or climb grass stems in search of aphids etc, but they are thought to be primarily specialist predators of various Chrysolina eggs and larvae on which their larvae are also parasitic. Breeding occurs in the spring when pairs mate on the ground and climb the stems of various herbaceous plants such as thistles, Hawkweeds, St. John’s worts and yarrow and they may also be found among foliage on trees and shrubs, this is probably how they detect their larval host and find suitable places for laying eggs, at this time the adults may be swept from vegetation in numbers but they are otherwise solitary and will generally be found as single specimens. First instar larvae are of the normal carabid type, slender and agile, and will predate small animals such as worms, molluscs and insects as they search for a host Chrysolina larva or pupa. The preferred host is a fully-grown larva within its prepupal or pupal cell, and once located the Lebia larvae will feed and grow rapidly but without moulting, the larva becomes greatly distended with its various tergites appearing as small plates on the soft integument of the swollen body. At this fully-grown stage it will moult to produce a non-feeding second instar stage which has reduced appendages and mouthparts, this stage is brief and a further moult soon occurs to produce the pupa, the entire development from egg to adult is rapid and may take only two or three weeks. There is only a single generation each year but adults remain active until late in the autumn before entering tussocks to overwinter, often alongside adults of their host species. Adults are fully-winged and capable of flight but this is rarely observed.
4.8-8.5mm. Broadly-oval and rather flattened, this species is easily recognized on colour alone; head and elytra shiny metallic green or bluish green, pronotum and scutellum red, ventral surface of head and abdomen metallic blue, all thoracic segments red or orange, legs pale red with the tarsi and sometimes the tibial apices dark, antennae dark two basal segments and often the base of the third segment pale. Head smooth and finely punctured, with convex and protruding eyes and temples strongly converging to a short neck. Pronotum transverse, widest in front of the middle and rounded laterally to protruding posterior angles, surface smoothly convex and finely and sparsely punctured, explanate margin narrow anteriorly and broadened before the base, without basal fovea but slightly depressed before an extended basal margin. Elytra with rounded shoulders and dilated towards roundly-truncate apical margins, striae finely punctured throughout, interstices randomly and finely punctured; more finely so than the striae, marginal interstice with a series of widely separated deep pores. Claws dentate in both sexes, male with basal pro-tarsal segments dilated.