Cercyon haemorrhoidalis (Fabricius, 1775)
Widely distributed, occurring throughout mainland Britain, Scilly, anglesey, the Western Isles, Orkney and Shetland (NBN). Lack of records from the Isle of Wight and the Isle of Man seems likely to be due to lack of recording activity as the species is otherwise generally abundant (Skidmore). Common and usually abundant throughout the Watford area where the adults become active during the first warm days of spring; in the first week of March 2008 we netted them in flight in warm sunshine throughout Whippendell wood and along the canal margins which border dung pasture near the A412. They soon become abundant, occurring in herbivore dung in just about any situation. In late spring adults appear within days of the cattle arriving on Common moor and are soon abundant both in dung and, during hot weather, in flight. They may also be found in various types of decaying vegetable matter; we have extracted them from piles of rotting grass cuttings on West Herts golf course, from compost heaps in several town centre gardens, from deep within heaps of decaying pond clearance below Cassiobury park and, in large numbers, from decaying terrestial bracket fungi beneath fagus in Whippendell wood during the autumn of 2006. The species comes readily to light in many situations; on warm July and August evenings on Common moor they will be attracted in large numbers. Hansen records the species from flood debris, carrion, at sap and in the nests of various birds.

Due to its abundance this species will soon become familiar in the field, especially when working dung pasture. Extensively red species resemble in colouration and size the equally abundant C.melanocephalus and both are often found together, the best field characters are the triangular dark elytral markings and dark epipleurs of melanocephalus, both characters can be appreciated in good light with a X20 lens.

2.5-3.1mm (Vogt, 1971) A broadly oval and convex species, shiny and usually extensively darkened. Head shining black, quite densely and strongly punctured, without microsculpture. Widest at eyes which produce but form a continuous outline with head, strongly narrowed in front of eyes, front margin of clypeus straight. Palps and antennae black or very dark brown. Pronotum entirely shiny black (examine lateral margins), puncturation a little finer denser than on head. Lateral margin bordered and evenly curved from weakly protruding front angles to obtuse hind angles, basal margin strongly sinuate. Surface smooth in front of basal margin, without fovea or longitudinal impression. Viewed from the side the pronotum and elytra form a single curve(cf. C.ustulatus). Scutellum shiny black, punctured as surrounding elytra. Elytra usually extensively darkened although at least some dark red colouration is generally visible under strong light, usually near suture or around the humeral area. Lateral margin and apical area yellow. Sometmes the elytra are extensively red or orange with only the sutural margins and base dark so forming a T, never with the triangular black marks characteristic of C.melanocephalus. Epipleurs light, generally pale brown or orange. Cuticle shiny, without reticulate microsculpture, becoming dull in apical half. Interstices flat, finely and distinctly punctured between well impressed, punctate striae which are weaker in basal half. Apex produced, usually strongly but sometimes (rarely) almost straight. Legs testaceous, tarsi paler. Tibiae with a series of short spines on outer edge and strong apical spurs. Protibiae rounded at apex. Tarsi 5-5-5. Basal segment of meso and meta tarsi elongate, longer than second.

Description from 12 Watford specimens at X40

Vogt, in Freude,H., Harde, K.W. and Lohse, G.A. 1971 Die Kafer Mitteleuropas Vol 3 pp 130-139