Micridium halidaii (Matthews, 1868)
POLYPHAGA Emery, 1886
STAPHYLINOIDEA Latreille, 1802
PTILIINAE Erichson, 1845
Micridium Motschulsky, 1869
As with many of these tiny and neglected species the distribution is probably only poorly understood, but thus far the species is known to be widespread in Central and Northern Europe; it is recorded from Austria, Belarus, Western Russia, Czech Republic, Denmark, France, Germany, Poland (where its presence was confirmed in 2015), Romania, Slovakia, Switzerland, Sweden and Finland, and Sicily seems to be the only Mediterranean island with records of the species. Records are generally few and far between except for Sweden, where it is frequently recorded from southern provinces bordering the Baltic, including Gotland, and some northern provinces near the Arctic Circle. Known in the UK from only a few sites in south-eastern and Central England but despite being very local and scarce it is sometimes common where it occurs. UK records are from ancient woodland pastures where adults occur among decaying wood and bark of old Oaks and are thought to be associated with mycelia of Laetiporus sulphureus. Adults have been recorded year-round on the continent with peaks in abundance during May and June, and again during August and September.
0.58-0.63 mm. Elongate and discontinuous in outline, body smooth and shiny, without microsculpture, pale brown with recumbent creamy pubescence, appendages often a little lighter. Head broadest across convex and prominent eyes and narrowed to a rounded anterior margin, temples short and converging, vertex flat, clypeus weakly convex, surface extremely finely punctured. Antennae inserted laterally in front of the eyes, 11-segmented and more or less filiform; segments 9-11 are longer and slightly wider than preceding segments but do not form a club, two basal segments short and much broader than the others, segments 6-8 smoothly narrowed from the centre; not constricted before the base. Pronotum transverse, broadest slightly in front of the middle and smoothly narrowed to rounded anterior angles and obtuse posterior angles, apical and basal margins straight and about equal in length, surface with an oblique furrow either side of the disc (but without a central depression), these begin at the base outside the base of the scutellum and converge to beyond the middle. Prosternum without a distinct keel, front coxae meeting at the middle, middle coxae narrowly divided by a pointed mesosternal process, hind coxae broadly divided. Scutellum large and equilateral. Elytra elongate, broadest at or in front of the middle and smoothly curved from sloping shoulders to separately-curved apical margins, surface randomly and finely but always distinctly punctured, lateral margins smoothly deflexed; the epipleura not delimited by a keel. Legs long and slender, middle tibiae broadened internally before the apex. Tarsi 3-segmented, the terminal segment slender and longer than the others combined. The sexes are very similar but in males the plate between the hind coxae has an apical fringe of short bristles.