Aplocnemus nigricornis (Fabricius, 1792)
POLYPHAGA Emery, 1886
CLEROIDEA Latreille, 1802
RHADALINAE LeConte, 1867
Aplocnemus Stephens, 1830
This Western Palaearctic species occurs throughout Europe from the Pyrenees to Italy and Greece in the south and north to the UK, Denmark and the Baltic countries where it reaches into some central provinces of Norway, Sweden and Finland; it is locally across Central and Southern Europe but otherwise sporadic and generally scarce e.g. it is frequent in southern parts of Fennoscandia but has not been recorded from Poland since the 1980s. In the UK it is widespread but very local and scarce in Southern and Central England and Wales although our other species, A. impressus was formerly confused with this species and so many older records may be unreliable. The typical UK habitats are ancient deciduous woodland and wooded pasture and here there may be an association with old hollow oaks (Quercus L.), in much of Europe it is mainly associated with conifers, especially pines (Pinus L.) and spruces (Picea Mill.) although in Sweden it also often occurs on birches (Betula L.) and Aspen (Populus tremula L.). Adults are active from April until July and peak in abundance during June. They diurnal and they fly well, visiting flowers and blossom in warm weather but otherwise remain on trees or under bark, little is known of the biology but the predatory larvae are known to develop under bark or among decaying wood during the summer, it is also likely that adults are fully formed by late summer as small numbers have been recorded throughout the year. Adults may be sampled by inspecting trunks and fallen timber or by sweeping flowers and blossom and they are likely to appear in suitably placed flight-interception traps.
4.0-4.8 mm. Elongate and discontinuous in outline, dorsal surface dark metallic green or blue with long semi-erect and erect pubescence, antennae dark with several pale basal segments, legs pale brown. Vertex flat and finely punctured between large and prominent eyes, temples short and converging, clypeus produced and angled beyond the antennal insertions. Maxillary palps securiform, antennomeres 4-10 serrate, terminal segment elongate and rounded apically. Pronotum transverse, broadest at or behind the middle and smoothly narrowed to rounded angles, surface weakly convex and narrowly explanate, finely but not densely punctured, about the same as the head, and with mostly erect pubescence. Scutellum widely triangular and curved laterally. Elytra elongate and only slightly broadened from angled shoulders to a continuous apical margin, lateral margin at most only weakly crenulate, surface smooth and shiny between random and rather strong punctures, without striae or micropunctures, pubescence mostly semi-erect with isolated erect setae. Tibiae slender and with tiny apical spurs, tarsi 5-segmented; basal segments weakly lobed and the apical segments long and thickened towards the apex. Claws smooth and without a basal tooth, at the base of each there is a pale membrane which is obvious in fresh specimens but soon shrinks and resembles a long appendage below each claw so that they sometimes appear doubled, this feature will distinguish Aplocnemus from superficially similar species of Dasytes. Distinguished from A. impressus by the colour, much more weakly crenulate elytral margin and erect setae among the elytral pubescence.