Leistus rufomarginatus (Duftschmid, 1812)
A native of central and eastern Europe extending through Russia, Ukraine and Asia Minor, this species has expanded north and west in recent decades and is now established through much of western Europe and reaches north to the UK, Sweden and, since 2017, Norway, this northwards expansion is thought to be due to milder winters. It was first recorded in the UK in 1942 and is now locally common throughout England, Wales and Scotland north to Inverness, the first record from Ireland was in 1996 and it is now widespread in the north. Adults occur year-round, they overwinter among litter or under logs etc but are often active during mild spells, typical habitats include rather open woodland e.g. beech woods, and wooded borders but they also occur in more closed and darker situations and below hedgerows etc. They become active very early in the year and are generally nocturnal, they remain among litter or under logs or bark etc. during the day and become active at night when they may be found by searching around the base of trunks or among logs on damp soil or litter, they are easily seen by torchlight but they can run fast and will generally hide in cracks in the soil or among litter when disturbed. Both brachypterous and macropterous adults occur but it is not known if they can fly and the mode of dispersal is not well understood. Adults and larvae overwinter and new generation adults eclose during late May and June, they feed until the warmest part of the summer when they enter the soil, often in groups, to aestivate until late August or September. Mating and oviposition occurs in late summer and autumn and some of these adults will go on to overwinter but most will die off before the following spring. Larvae develop through the winter and pupate in the soil during the following spring to produce adults from May, and along with other members of the genus both larvae and adults are specialist springtail predators.
The overall appearance will soon make this a familiar species; distinguished among our fauna by the dark, non-metallic dorsal surface with broad red margins to the pronotum and elytra. 8-9.5 mm. Dorsal surface dark brown to black and lacking a metallic reflection; head black with the mouthparts and antennae entirely pale, the vertex is smooth and shiny; at most indistinctly wrinkled beside and in front of the eyes, the antennae are long and slender and segment is distinctly longer than the third. Pronotum strongly transverse, about 2:1, broadest in front of the middle and evenly narrowed to obtuse or, in fine detail, almost perpendicular, hind angles which bear a setiferous puncture. The disc is smooth and shiny and the explanate margins broad and punctured. Elytra characteristically elongate and narrow, up to twice as long as broad, and bearing a small shoulder tooth-an extension of the basal border-which may be hardly discernible, and punctured striae well-impressed to the apex. The interstices are weakly convex and finely punctured.