Rhagonycha nigriventris Motschulsky, 1860
POLYPHAGA Emery, 1886
ELATEROIDEA Leach, 1815
CANTHARINAE Imhoff, 1856
CANTHARINI Imhoff, 1856
Rhagonycha Eschscholtz, 1830
More generally referred to in the literature by the older name of R. limbata Thomson, C.G., 1864, this species occurs across the Palaearctic region from France to Mongolia and eastern Siberia, in Europe it is generally common and often abundant from lowlands to the tree line in mountain areas in central and northern regions but absent from many Mediterranean countries including Italy, most of the Balkans and Asia Minor, to the north it reaches the UK and the far north of Sweden and Finland but is absent Norway. It is generally common throughout the UK north to Orkney and the Western Scottish islands and in Ireland is common in the north but very local and scarce in the south. Adults occur from early May until early July in open dry grassland and scrub, they often occur on disturbed land and may be common in parkland and gardens, they will usually be found by sweeping long grass and mixed herbage but they fly well and visit a range of flowers, more especially umbels and, early in their season, hawthorn blossom where they may occur in numbers and will often be found mating. Both adults and larvae are predaceous, adults hunt small insects among foliage and flowers while the larvae are terrestrial and hunt nocturnally; they develop through the summer and autumn and overwinter in the ground although they are often active on the surface during mild spells, they finish developing and pupate in the spring. In northern continental regions the species is also, or even mainly, hygrophilous and associated with a range of wetland habitats including peat bogs, carr and riparian forests.
Adults are small, 5-6mm, but very distinctively coloured and so with a little practice should easily be identified in the field. Head black, evenly convex and very finely punctured and pubescent, eyes small but convex and protruding, temples long and curved, palps black or very dark brown; the terminal segment securiform, antennae dark grey with at least two basal segments pale. Pronotum quadrate or slightly transverse, pale brown or reddish brown with a variable but characteristic dark central marking which does not extend to the anterior or posterior margins, finely and sparsely punctured and pubescent and slightly dull when compared with the head due to microsculpture which is just visible at X20. Scutellum black. Elytra with rounded shoulders and weakly dilated to separately-rounded apical margins, the surface without striae or longitudinal ridges (although these may be barley suggested on the disc), very finely punctured and with pale, semi-erect pubescence. Front femora darkened at least in the basal third, middle and hind femora dark except for the apex, tibiae entirely pale, at most only obscurely darkened, tarsi mostly dark grey or black. Tarsi 5-segmented, the third expanded but not bilobed, claws split longitudinally.