Acrolocha sulcula (Stephens, 1834)
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POLYPHAGA Emery, 1886
STAPHYLINOIDEA Latreille, 1802
OMALIINI MacLeay, 1825
Acrolocha Thomson, C.G., 1858
A Western Palaearctic species with a rather limited distribution; extending from Spain to Italy and Hungary in the south and north to the UK, Denmark and the Baltic countries where it reaches into southern provinces of Fennoscandia, so known from North Africa but not recorded from many of the Mediterranean islands. The species is known mostly from lowland situations; in Southern and Central Europe it is very local and generally rare but it becomes less so further north and it is locally common in Southern Sweden. With the exception of the West Country it is widespread in England and Wales; it is locally common in Kent, parts of the midlands and East Anglia, but otherwise very local and uncommon. Adults are present year round but are recorded mostly in late summer and autumn; they appear in numbers during July and peak in abundance from late August until October, otherwise appearing as odd specimens. The usual habitat is any type of dung, but often horse or cattle dung, but they may also occur more generally in decaying vegetation; straw, compost, decaying terrestrial fungi, and they have been found in numbers among decayed sedge and reed litter. Little is known of the biology but it is likely that breeding occurs from late spring and that larvae develop through the winter and pupate the following spring to produce adults during summer and autumn. Adults may be sieved from old and dry dung or compost etc, but they are mostly nocturnal and often active on the surface of dry dung etc at night, they occasionally climb grass stems and they fly well, sometimes swarming in large numbers over dung pasture as the light fades, and sometimes attracted to light traps.
1.5-2.8 mm. Elongate, broad and discontinuous in outline, body black to dark brown, usually with the elytra and margins of the abdominal tergites paler, glabrous but for extremely short and fine hairs on the abdomen, antennae dark with one or two pale basal segments, legs pale brown, usually with the tibiae darkened apically. Head transverse, broadest across large and prominent eyes, temples strongly narrowed to a broad and almost parallel-sided neck, surface unevenly convex (but without distinct furrows or depressions), with rather random and strong cellular microsculpture and two ocelli in line with the posterior margin of the eyes. Terminal maxillary palpomere much longer and about as wide as, at least across the base, as the penultimate segment. Antennae mounted laterally in front of the eyes; 11-segmented; segment 3 broadened from a very narrow base, and segments 7-11 broader and more pubescent than segments 3-6. Pronotum transverse, broadest about the middle and narrowed to widely-rounded anterior angles and obtuse posterior angles, lateral margin smooth, all margins finely bordered, surface rather flat with at most weak depressions on the disc, microsculpture similar to that on the head but usually more uniform. Elytra quadrate or nearly so, weakly dilated from rounded shoulders to an almost continuous apical margin, surface without striae but with uneven and sometimes rather oblique longitudinal impressions that are often confused by large and strong cellular microsculpture. Abdomen broad and strongly tapering apically, basal tergites strongly bordered, second visible tergite with a small patch of pubescence either side of the middle, all tergites with dense cellular microsculpture and, at most, extremely fine and sparse punctures. Legs short and slender, all tibiae with several rows of short spines externally and short apical spurs. Tarsi 5-segmented, basal segments not expanded or densely pubescent below, terminal segment about as long as the others combined. Easily distinguished among our fauna by the microsculpture to the head, pronotum and elytra which consists of meshes united at fine punctures, coupled with the very narrow base of the third antennomere.