Catops tristis (Panzer, 1794)
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POLYPHAGA Emery, 1886
STAPHYLINOIDEA Latreille, 1802
CHOLEVINAE Kirby, 1837
CHOLEVINI Kirby, 1837
Catops Paykull, 1798
This mostly central and northern European species is generally considered to be the most orophilous (species which thrive in subalpine environments) member of the Cholevinae, it is very sporadic and local in the south from Spain to Italy and Romania where it is it most frequent in mountain areas, and to the north it is locally common from lowlands to sub-alpine altitudes and extends to the UK and above the Arctic Circle in Fennoscandia although it is absent from many of the southern Baltic countries and in some areas e.g. Poland, abundant only in Alpine regions. In the UK it is locally common across England and Wales, becoming scarce in the north and extending sporadically into the Scottish Highlands, it has also recorded from Ireland. The nominate subspecies occurs throughout this range while ssp. infernus Szymczakowski, 1957, an Ice Age relic restricted to caves where it breeds among guano and other organic matter, is known only from Poland. Adults occur year-round; they often appear during mild winter spells and are active over a long season from February or March until late in the autumn, peaking in abundance during May and June and from August until October. Adults are most frequently recorded from carrion, leaf-litter and, later in the year, decaying fungi, and while they seem to prefer open situations may occur in most habitats with suitable host material. They are also associated with subterranean mammal nests and this may be an important overwintering habitat, in the UK mostly with mole, rabbit and fox but on the continent frequently in badger and marmot nests and they are also recorded from wasp (Vespula vulgaris L.) nests. Larvae develop rapidly during the spring and summer; they feed on carrion and organic detritus but are also coprophagous, preferring non-herbivore dung. In certain areas of southern Europe e.g. the Pyrenees, Carpathian Mountains and the Balkan Peninsula, they are frequently common in caves. Adults may be found in abundance at carrion and sometimes in other decaying organic matter, they sometimes appear in pitfall traps placed close to mammal burrows and are regularly recorded at light.
3.0-4.5 mm. Elongate and discontinuous in outline with the pronotum and elytra separately and rather strongly rounded, colour varies from entirely dark chestnut brown to bicoloured with the forebody darker than the elytra, often dark grey or almost black, legs brown, antennae dark with the basal four or five segments and the apex of the terminal segment brown, entire dorsal surface with fine, creamy and recumbent pubescence. Head transverse and evenly rounded from above, surface convex and without structure, the occipital crest resting against the pronotal margin and the frontoclypeal suture at most only weakly defined, eyes convex and almost continuous with the outline. Antennae expanded from the seventh segment; the fifth segment clearly elongate, the sixth slightly elongate in the male and quadrate or slightly transverse in the female, and the seventh more than 1.5X wider than the sixth. Pronotum transverse and broadest about the middle, all angles obtuse and the base slightly narrower than the elytral base, surface evenly convex and with close oblique punctures that face backwards, resembling a rasp. Elytra broadest in the basal half and smoothly curved from rounded shoulders to a continuously-curved apical margin, lateral margin strongly bordered, especially in the basal half, surface finely and densely punctured throughout, with well-developed and arcuate sutural stria and traces of longitudinal impressions across the base but otherwise without striae. Legs long and slender, all tibiae with a strong apical spur and fine stiff setae along the external margin. Tarsi 5-segmented, basal segments of front tarsi dilated, all segments of middle and hind tarsi simple. Species of Catops are closely similar and determination is often best by dissecting males and assigning females by association (although several species often occur together at carrion), in the present species the median lobe is narrowly rounded and weakly arched apically and there are no marginal ridges on the dorsal surface. Typical specimens soon become obvious but a more elongate and usually darker form, sometimes referred to as var. montivagus Heer, is best distinguished by dissection.