Leistus spinibarbis (Fabricius, 1775)
This is a western Palaearctic carabid with six described subspecies; L. s.str. is western European, occurring from Spain to Italy and Germany and extending into the Netherlands and the U.K., ssp. rufipes Chaudoir, 1843 occurs in southeast Europe and is sympatric with the nominate subspecies in the western part of its range, ssp. ponticus Kryzhanovskij & Shilenkov, 1999 occurs in Ukraine and Russia, ssp. abdominalis Reich & Saulcy, 1855 is from Israel and Syria, while in northwest Africa ssp. afer Coquerel, 1859 is restricted to Algeria and Tunisia, ssp. fiorii Lutshnik, 1913 is endemic to Italy. It is common throughout England and Wales becoming scarce and very local in Scotland. The typical habitat is rather dry and open situations exposed to the sun; open woodland and wooded borders, especially in the north, wasteland, grassland, parkland and gardens. Adults spend the day under debris, bark or among litter, often in pairs or small numbers and often with other carabids; they are active nocturnally and readily found around the base of trees, on logs or among grass. New generation adults appear in late spring and early summer and feed for a few weeks before entering an aestivation period during the warmest parts of the summer, they emerge in late summer and resume feeding before mating and ovipositing in the autumn, many survive through the winter and into the spring but the majority will die off after reproducing. Larvae develop through the winter and pupate in the soil in the spring. Both adults and larvae are specialist Collembola predators.
At 8-10.5mm this is our largest member of the genus, it may be recognized in the field by the brilliant blue colouration, the darkened femora and, unique among our species, the darkened basal segments of the antennae. Doubtful specimens might be mistaken for fulvibarbis but the pronotum is distinctive; less transverse and evenly narrowed to finely denticulate hind angles, lacking the sub-basal parallel margin seen in that species. The head is smooth and finely punctured, distinctly wrinkled beside and in front of the eyes, and without the larger punctures seen in montanus. Mouthparts entirely pale. Pronotal explanate margins wide and distinctly punctured, often with the lateral margin narrowly red, and with a setiferous puncture at the base. Elytra rather broad and flat with denticulate shoulders and strongly impressed and punctured striae to well behind the middle, becoming weaker and smooth towards the apex. The legs vary from entirely pale to entirely dark, but typically they are pale with at least the basal part of the femora darkened.