Amara plebeja (Gyllenhal, 1810)
A very widely distributed and generally common species throughout Europe from Northern Italy, Yugoslavia Romania and Ukraine north to the Arctic circle in Scandinavia and east through Siberia to northern China; in the UK it is common and often abundant north to Angus and local and scattered further north including the Western Isles. Often described as eurytopic this species inhabits two distinct habitats; through the spring and summer it occurs in open, often damp, situations such as grassland, agricultural headlands or among vegetation near water although it is not riparian, and through the winter in drier habitats, often among tussocks or under logs in woodland or along wooded borders. Adults migrate from their overwintering sites by flight in the spring and at this time may disperse to new habitats; once established their flight muscles are autolysed and they remain localized until the autumn when their muscles develop once more prior to migration to their overwintering sites by flight. They breed in the spring and larvae develop through the spring and summer to produce adults from July or August, they are long-lived and both old and new generation adults occur at both summer and winter sites, there may be a short diapause when adults enter the soil during the warmest part of the summer and then a peak in abundance as they emerge alongside new-generation adults. Both adults and larvae are known to be seed-feeders. Adults may be found at night on pathways etc., often in numbers and often among populations of other common carabids e.g. Harpalus affinis (Schrank), Poecilus cupreus (Linnaeus) or Amara aenea DeGeer, although this last species generally inhabits much drier situations, and in the spring and autumn they occasionally occur at light traps or by sweeping vegetation. Specimens will also occur occasionally in very dry habitats, including domestic gardens and parks.
This is one of only two species of subgenus Zezea Csiki, 1929 to occur in the UK, they are unique among our fauna in having the pro-tibial spur trifid; our other species, A. strenua Zimmermann, 1832 is distinctly larger, 8.0-9.6mm, the pronotal base is largely unpunctured and the anterior angles only weakly projecting. In the field plebeja can sometimes be identified by a bicoloured body, the foreparts greenish and the elytra contrasting faintly purple but specimens will generally need to be examined carefully to produce an accurate identification.
6.3-7.8mm. Dorsal surface shiny metallic bronze or with various coloured overtones, head and pronotum with weak and indistinct microsculpture. Antennae black with segments 1-3 and the base of 4 pale yellow or orange, palps entirely black or sometimes lighter at the tips. Eyes moderately convex, with distinct longitudinal furrows and 2 supra-orbital setae internally. Pronotum transverse, almost parallel-sided in the basal half, with strongly protruding anterior angles and a sinuate basal margin. Basal fovea doubled, the inner often represented by a longitudinal streak, as in A. aenea, punctation in basal third irregular and rather strong. All elytral striae distinct to the apex, scutellary striole with a distinct pore at the base, and there are usually with 2 preapical punctures adjacent to the seventh stria. Leg colouration usually strongly contrasting; black femora and tarsi and pale tibiae. Male basal pro-tarsal segments dilated.