Cercyon terminatus (Marsham, 1802)

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POLYPHAGA Emery, 1886

HYDROPHILOIDEA Latreille, 1802

HYDROPHILIDAE Latreille, 1802

SPHAERIDIINAE Latreille, 1802

Cercyon Leach, 1817

Cercyon Leach, 1817

This widespread Palaearctic species is generally common from lowlands to middle mountain altitudes from the Pyrenees to Siberia, China and the far east of Russia; it is common in north-west Africa and occurs on most of the Mediterranean and Atlantic islands. The European distribution is rather patchy; it extends continuously from France to Italy and northern parts of the Balkan Peninsula and north to the Arctic Circle in Fennoscandia but is absent from much of the south east and some of the Baltic countries. The species was thought to have been introduced into the United States in the 1800s but archaeological evidence shows that it was established around Boston by the late 1600s, it is now widespread though sporadic and rarely abundant across The United States and Canada, except for northern Parts, but its origins remain unclear. In the UK it is generally common across southern and central England and Wales and much more local and rare in the West Country and further north to the Scottish Highlands, there are records from Scilly, Anglesey and Man and it is very local and mostly coastal in Ireland. Adults are present year-round; they overwinter among decaying organic matter and are active from early spring until late in the year, peaking in abundance from June to August. The typical habitat is herbivore dung, mainly cattle and horse dung, but they may occur among decaying vegetation in a wide range of habitats, including wetland margins, and may be common among garden compost and grass clippings, they occasionally occur at carrion and we have found them among decaying seaweed. They are good fliers and during warm weather will sometimes swarm over dung pasture in large numbers; they also fly at night and are attracted to UV light. Sampling is easiest by working dung; they are often among the earliest species to arrive at freshly deposited dung, especially horse dung on bridle paths through wooded areas, but they also occur in old dry samples in the autumn. Sieving compost or well-decayed leaf litter is often productive and they regularly occur among winter flood refuse. During the warmer months they usually occur in large numbers, especially among manure or decaying straw, but often along with other small Cercyon and so will need to be taken for critical examination. The species is univoltine, mating pairs will frequently be found through the spring and fresh adults occur during late spring and summer. Typical of the group, adults are thought to be mostly saprophagous while larvae are mostly predatory.

Cercyon terminatus 1

Cercyon terminatus 1

At 1.6-2.3mm this is among the smallest of our UK members of the genus. Elongate-oval and continuous in outline, dorsal surface glabrous, head and pronotum black to dark brown, sometimes with the anterior pronotal margin a little paler, elytra variable from dark to pale brown, usually with a darker triangular mark below the scutellum, appendages pale brown, sometimes with the antennal clubs darker. In side view the pronotum and elytra are equally convex and form a continuous curve. Head produced and narrowed in front of rounded (not excised) eyes, weakly convex and finely and rather densely punctured, anterior clypeal margin truncate, not sinuate or concave. Maxillary palpi about as long as the antennae, the second segment elongate and expanded from the base and the penultimate and terminal segments long and slender. Pronotum broadest across obtuse posterior angles, smoothly convex and evenly curved laterally (not sinuate towards the base), without impressions and punctured about the same as the head. Mesosternal process moderately broad, smoothly convex (not keeled) and meeting or slightly overlapping the basal margin of the metasternum which is produced forward but not notched. Metasternum without oblique lines from the central raised area. Elytra broadest in front of the middle and smoothly narrowed to a continuous and rounded apical margin, lateral margin smooth throughout (without an impression below the shoulder) and with very narrow epipleura, surface with impressed and punctured striae complete to the apex, the outer stria (number 10) more finely punctured than the others. Interstices flat across the base, becoming slightly convex towards the apex, with fine but distinct microsculpture and fine punctures throughout although the punctures often fade towards the apex. Legs short and robust. Front tibiae rounded apically, middle and hind tibiae truncate, all with stout spines along the external margin and paired apical spurs. Tarsi 5-segmented; the basal segment of the middle and hind tarsi much longer than the following segment.