Agonum fuliginosum (Panzer, 1809)
This is a generally common species from lowlands to boreal regions up to about 1200m throughout central Europe from France to northern Italy, Caucasus and western Siberia, extending to the far north of Fennoscandia and the UK where it is common and often abundant throughout including all the islands to Shetland. Adults occur year-round and are active over a very long season, from early spring until late in the autumn or into the winter depending on the season, peaking in abundance during March and April. In northern regions, including the UK, it is more or less confined to wetland habitats, especially where they are shaded; water margins, fens, marshes and peat bogs etc but in more southern European areas they are more prevalent in damp deciduous and mixed forests and less often occur in wetlands. Adults are predominantly nocturnal when they are easily recorded among vegetation and debris on permanently damp soil near water, by day they remain hidden under logs or loose bark and will often be found alongside other carabids such as Paranchus albipes (Fab.), Agonum emarginatum (Gyllenhal), A. thoreyi Dejean or Pterostichus minor (Gyllenhal). They overwinter under logs or loose bark on fallen willow branches etc. and often in numbers, sometimes in large aggregations, and in the spring they are often the first carabids to be found in such situations. Mating occurs through the spring and early summer and larvae emerge from June, they complete their development during the summer and new-generation adults appear over a long season from August to December. Both adults and larvae are predatory, feeding on various small animals such as mites and aphids but the main prey, at least for adults may be small springtails. The proportion of fully-winged to brachypterous specimens varies in Europe and may be influenced by habitat but the majority of UK specimens are brachypterous. Adults are readily sampled by pitfall trapping in most wetland habitats and will often be found to be the most abundant medium-sized carabid present.
5.5-7.0mm. An elongate and slender species with long appendages; body glabrous, entirely unmetallic black or with dark brown elytra, antennae black or with the basal segment dark brown, legs dark brown, often with the femora darker, almost black. Head, including the neck, smooth, without deep furrows, with two setiferous punctures by the inner margin of each eye, mandibles sharp apically and without a setiferous puncture on the outer face, palps dark or with the apex of each segment pale; penultimate labial palpomere with at most a pair of setae on the inner margin, terminal segment of all palps long and well-developed. Pronotum transverse and evenly rounded laterally to weakly protruding anterior angles and rounded hind angles, lateral explanate margin narrow throughout. Elytra evenly curved laterally to a continuously rounded apical margin, basal border abruptly angled at the humerus and epipleural margin not crossed with the elytral margin before the apex, striae narrow and well-impressed to the apex, without distinct punctures although there are usually a small number of setiferous punctures in the third interstice adjoining the second and third striae, interstices only very weakly convex. Legs long and slender, fore tibia with a deep antenna-cleaning notch, and all tibiae with a single long spur on the inner apical angle. Tarsi glabrous; each segment with stiff setae but without fine pubescence, hind tarsi with a variously developed, usually weak and partial, lateral furrow, claws smooth. Basal segments of pro-tarsi wider in the male.