Dactylosternum abdominale (Fabricius, 1792)
POLYPHAGA Emery, 1886
HYDROPHILOIDEA Latreille, 1802
SPHAERIDIINAE Latreille, 1802
Dactylosternum Wollaston, 1854
With an almost cosmopolitan distribution this species is generally common in tropical and sub-tropical regions but less so and rather patchily distributed in northern temperate regions; it occurs throughout the Palaearctic region from Europe and North Africa to China and Japan and including the Mediterranean and Atlantic islands, it is widespread in North America and often abundant in southern regions and on many of the Caribbean islands. The origin of the species is unknown but it seems to be most closely related to endemic Pacific and New Caledonian species. The species is partly synanthropic and so much of the expansion has been due to trade; in tropical regions it is often associated with banana roots and residual rhizomes following harvesting, here it is considered to be an important predator of weevil pests etc. and this association alone may have contributed to its spread into temperate regions. Much of the temperate expansion seems to have occurred during the 20th century and is ongoing; the species is widespread in Europe and generally common in Mediterranean regions, but while it is spreading north into the UK it is thus far generally absent from the Baltic region, but this is likely to change as it was only recently recorded from e.g. the UK, Hungary and northern Germany. It was first recorded from the UK in 2003 and has since become widespread and locally common across much of southeast England. In temperate regions it is generally associated with decaying organic matter such as leaf-litter, decaying fungi and rot holes in old trunks etc. but they more often occur near human habitation in manure and silage and frequently among domestic waste stored in bins. Adults are present year-round; in warmer regions they are active throughout the year but in temperate regions only during spring and summer when they have two peaks in abundance, during spring and late summer, they fly well and can be quick to colonize new sites. Females produce small numbers of eggs in flat silken cases attached to host material in spring and early summer and larvae predate small insects and their larvae. Development depends on conditions but larvae are usually fully-grown within three or four weeks and they complete cycle from egg to adult takes between four and six weeks. The species is likely to be univoltine in the UK. Adults are primarily saprophagous but may also be partly predatory, they may be sampled by sieving suitable material and here they often occur in numbers, they may also occur in tussocks and old straw etc. and they are frequently attracted to light. In certain parts of the world they frequently occur in maritime habitats and may be common among decaying carrion on beaches.
3.8-5.4 mm. Elongate and continuous in outline, dorsal surface glabrous and finely punctured throughout, black to dark brown or with the forebody a little paler than the elytra, palps and antennae bright yellow but for the antennal clubs which are at least in part darkened, legs dark brown. Head smoothly convex between weakly convex and incised eyes and strongly converging temples, cheeks rounded laterally and covering the antennal insertions, anterior clypeal margin notched medially. Antennae 9-segmented; the basal segment as long as the next five together and the last three form an elongate club. Pronotum widely transverse, broadest at acute posterior angles (from above) and smoothly narrowed to weakly projecting anterior angles, surface evenly convex, without impressions or structure. Elytra almost parallel-sided from angled shoulders to a continuous apical margin that completely covers the abdomen, each with ten punctured striae which fade before the base and become deeper apically. All tibiae with several fine spines along the external margin and strong terminal spurs. Tarsi with five simple segments; the middle and hind basal tarsomere much longer than the second segment and he last segment elongate. Claws smooth and without a basal tooth.