Aploderus caelatus (Gravenhorst, 1802)
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POLYPHAGA Emery, 1886
STAPHYLINOIDEA Latreille, 1802
THINOBIINI Sahlberg, J., 1876
Aploderus Stephens, 1833
Present throughout Europe to the far north of Fennoscandia and generally common in central and northern regions, otherwise rather local except in mountain regions where it is common, also present in North Africa and recorded further east through Asia Minor and Russia to Siberia. In the UK it is widespread though very local and sporadic across Central and South Eastern England, it was formerly much more widespread, extending into Scotland and known from Ireland, but there seems to have been a general decline over recent decades and most modern records are from the south east and East Anglia. The species is associated with dung, compost and other decaying organic matter in a wide range of fairly humid habitats; grassland and pasture, parks and gardens, wasteland, woodland, wetland margins, heather moorland, peat bogs, dunes and coastal marshes, and adults have been found under bark and in subterranean mammal nests. Adults are present year-round; they overwinter among host material or in leaf-litter or tussocks etc., and are active over a long season from March until October, peaking in abundance between July and September. They do not diapause and may be active during all but the coldest winter periods, reproduction occurs in spring and autumn and there are two oviposition periods, the early one starting in April and the later one during October and November, these later eggs will overwinter to produce larvae in the spring alongside larvae from the early eggs. Larval development occurs between April and June and pupation occurs in June. New generation adults appear during July; these will aestivate during the summer and enter host material to feed before the autumn breeding period. Breeding and larval development is strongly influenced by temperature and so adults may appear earlier or later than usual; under laboratory conditions the time from egg to adult was 32 days at 25°C but increased to about 157 days at 10°C. Adults can be collected from dung or compost at any time but spring and autumn are optimum, they usually appear in numbers and sometimes swarm in flight on warm evenings or come to light or baited dung traps. A detailed account of the biology is given by Staniec (1998) and the developmental stages are described by Staniec (1997).
4.0-4.5 mm. Elongate and rather parallel-sided, forebody black, elytra pale to dark brown, abdomen black with terminal tergites paler, antennae dark with basal segments reddish below, legs brown. Head transverse (often more robustly developed in males) with small and weakly convex eyes and long curved temples, surface convex and usually longitudinally impressed, at least on the vertex, finely punctured and pubescent and with dense cellular microsculpture. Mandibles sharp and projecting forward, terminal maxillary palpomere narrow and pin-like. Antennae inserted anteriorly outside the base of the mandibles, weakly thickened from the base; three basal segments elongate, subsequent segments quadrate and becoming slightly wider towards the apex. Pronotum transverse, broadest behind perpendicular anterior angles and almost smoothly curved to a straight basal margin, lateral and basal margins smooth and finely bordered throughout, surface microsculptured as the vertex, sparsely punctured (these often in groups) and pubescent and with a longitudinally arcuate impression either side on the disc, centreline not impressed. Elytra quadrate to slightly transverse, parallel-sided or weakly dilated from rounded shoulders to straight apical margins, surface flat, randomly and closely punctured, sparsely pubescent and smooth, without microsculpture. Abdomen strongly bordered, tergites only weakly impressed across the base, sparsely punctured and pubescent and distinctly microsculptured, tergite 7 recurved apically, tergite 8 straight apically. External margin of front tibiae with a single row of fine spines in the apical half, middle and hind tibiae with a single long seta about the middle and very fine apical spurs. Tarsi 3-segmented; the curved terminal segment longer than the others combined. Claws smooth and not toothed at the base.