Habrocerus capillaricornis (Gravenhorst, 1806)
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POLYPHAGA Emery, 1886
STAPHYLINOIDEA Latreille, 1802
HABROCERINAE Mulsant & Rey, 1876
HABROCERUS Erichson, 1839
Habrocerus capillaricornis is native to the western Palaearctic and North Africa; it occurs throughout Europe north to mid-Scandinavia and is locally common throughout England and Wales although generally absent from the West Country and more sparse in the north, and there are a few records further north to the Scottish Highlands. Adults occur throughout the year in a range of habitats ( e.g. in Canada they have been recorded from the walls of a beaver lodge); under damp bark on both broadleaf and coniferous trees, among decaying fungi and compost and, through the winter, regularly appear among extraction samples of tussocks, fungi and leaf litter. They are also rather synanthropic and may soon appear in gardens in the spring among decaying grass cuttings and vegetable refuse. Mating and dispersal by flight occur in the spring when they sometimes appear at light, and larval development takes about a month during spring and summer, adults are probably mycophagous or saprophagous while larvae have been observed feeding on moulds. The tiny larvae are distinctive in having five pigment-spots arranged in an irregular line on each side of the head while adults may be recognized by the rings of setae around the apex of most antennal segments. This antennal feature is also seen in Trichophyinae but the two groups are readily separated on general morphology (see below). Adults are easily sampled by sieving suitable material over a sheet but they need to be looked for very carefully because, as well as the small size and rather nondescript appearance, they tend to run very rapidly and remain within the cover of debris on the sheet.
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2.5-3.5mm. very shiny black with the appendages, pronotal and elytral margins and abdominal apex variously pale. Head transverse and narrowed and produced anteriorly, eyes weakly convex and about the same length as the curved and strongly tapering temples, surface shiny and very finely and sparsely punctured. Antennae inserted laterally in front of the eyes, the insertions not visible from above, 11-segmented; all segments elongate, the 2 basal segments broad, the remainder long and slender, each with a ring of several long erect setae. Pronotum broadest in front of rounded posterior angles and roundly narrowed to obtuse anterior angles, anterior margin straight, posterior margin unbordered and weakly bisinuate, surface with scattered micropunctures and very fine, sometimes obliterated, transverse
microsculpture. Lateral margins with several long erect setae, generally 2 near the anterior angles, 2 behind the anterior margin and 4 along the posterior margin. Elytra slightly transverse, very finely and sparsely punctured and with transverse cellular microsculpture, all margins, including the sutural margin, very finely bordered, each elytron with 3 strong erect setae, one laterally near each angle and one in the anterior half. Abdomen broadest at the base and evenly tapering to a truncate apex, basal tergites strongly bordered, distal ones only weakly so, all tergites finely and densely punctured and pubescent, the distal segments a little less so, surface shiny and lacking microsculpture. Lateral margins of all segments with various long erect setae.
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Compared with Trichophya the eyes are larger and much less convex, and the antennae are inserted laterally, the insertions being covered by the lateral margin of the clypeus and so not visible from above; in Trichophya they are also inserted laterally in front of the eyes but on the upper surface so that the insertions are clearly visible from above.
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HABROCERINAE Mulsant & Rey, 1876
This is a small subfamily containing 2 genera and 26 species. Nominocerus Coiffait & Saiz, 1965 includes 6 species; 4 from southern Chile and 2 from southern Chile and southern Argentina. Habrocerus Erichson, 1839 is a Holarctic group (with 3 Nearctic species) of 20 species that is now much more widespread due to the spread, owing to human activity, of the widespread H. capillaricornis Gravenhorst, 1806, this species was first recorded from the United States in 1931 and has since spread to South America, Tropical Africa, Southeast Asia, Australia and New Zealand; it is also the only species recorded throughout much of Europe, including the U.K., but other species occur in North Africa, The Middle East, Greece and Turkey etc. and there is a Canary Island endemic, H. canariensis Assing & Wunderle, 1965. All species are associated with decaying leaf litter, fungi, wood debris and bark in woodland etc. They resemble small Tachyporinae but differ in the antennae which are long and slender and have rings of long setae around the apex of most segments; this feature is also seen in Trichophyinae (above) but these are distinct in having the meta-coxae transverse, in the present group they are triangular. The head, pronotum and elytra are smooth; without coarse punctures or sculpture and the whole body has prominent lateral setae. All tarsi are five segmented.