Pteryx suturalis (Heer, 1841)
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POLYPHAGA Emery, 1886
STAPHYLINOIDEA Latreille, 1802
PTILIINAE Erichson, 1845
Pteryx Matthews, C.G., 1859
A widespread western Palaearctic species occurring from Spain to Asia Minor in the south, and extending north to the UK, Denmark and the Baltic countries where it reaches the far north of Norway, Sweden and Finland, also known from many of the Mediterranean islands, though not in North Africa, and parts of Western Russia. Because of its small size and cryptic habits the species is likely to be under-recorded but it is locally common in central and northern regions and probably much more local in warmer parts of Europe. In the UK it is widespread though generally very local and scarce across England and Wales and there are records from Ireland. The species usually occurs under bark or among decaying wood, less often in sporocarps (recorded from Laetiporus sulphureus on the continent) or among nearby moss or leaf-litter; it often occurs on oaks (Quercus L.) or beech (Fagus L.) but has been recorded from a wide range of deciduous trees including limes (Tilia L.), alders (Alnus Mill.), poplars (Populus L.), willows (Salix L.), birches (Betula L.) and elms (Ulmus L.), and much less often from conifers including pines (Pinus L.) and Norway Spruce (Picea abies (L.)). In northern Europe it is also recorded from mammal and bird nests in wooded areas, and among nest material of the Wood ant (Formica rufa Linnaeus, 1761). Adults occur year-round, they are active from February until November and they peak in abundance during June and July and again in late summer. Little is known of the biology but both adults and larvae are thought to feed on fungal spores and/or hyphae, and larvae probably develop through the summer to produce a fresh generation in late summer or early autumn. Adults tend to be active in all but the coldest winter spells and so may be sieved or extracted from suitable samples at any time, they (at least some, see below) also fly and so may appear in flight-interception traps placed in suitable trees, they usually occur in numbers and sometimes alongside other members of the family.
0.75-0.85mm. Elongate and discontinuous in outline; the elytral base much narrower then the base of the pronotum, body rather shiny brown with recumbent pale pubescence, appendages pale brown. Two forms occur and both may be present in a single population; in apterous forms the wings are much reduced and not functional, the eyes are smaller and the body is pale brown, in alates the wings are fully developed and functional, the eyes are larger and more convex and the body is dark brown, sometimes almost black. Head broadest across the eyes and smoothly rounded anteriorly, surface evenly convex and extremely-finely punctured. Antennae inserted laterally in front of the eyes, the insertions hidden from above, 11-segmented; two basal segments enlarged, segments 3-7 elongate and narrow, 8-11 broader and forming a loose and narrow club. Pronotum transverse, broadest at or a little in front of the base and narrowed to obtusely-rounded anterior angles, posterior angles perpendicular or slightly obtuse, apical margin gently curved and much narrower than the basal margin, surface evenly convex, without depressions etc. and with very fine mesh-like microsculpture, especially towards the apical margin. Scutellum large and triangular with straight lateral margins. Prosternum not produced between the coxae. Front and middle coxae closely approximated, hind coxae widely separated, the metasternal margin between gently sinuate. Basal margin of mesosternum with produced into a sharp lateral tooth below the elytral humeri, then broadly-curved to the lateral margin of the middle coxae. Elytra elongate, broadest about the middle and evenly curved laterally from sloping shoulders to separately-curved and almost truncate apical margins, surface smooth and very finely punctured, without depressions or striae, epipleura demarked by a fine lateral keel which is visible from above, at least towards the base. Abdomen at least partly visible from above (there are usually two or three segments visible beyond the elytral apex but they tend to contract when drying and so only the apex may be visible in set specimens), pygidium smoothly rounded or with, at most, a single tiny tooth at the apex. Legs short and delicate with slender pubescent tibiae which lack apical spurs. Tarsi 3-segmented. The sexes are very similar and so specimens will need to be made translucent or dissected in order to be sexed.