Phloeocharis subtilissima Mannerheim, 1830
POLYPHAGA Emery, 1886
STAPHYLINOIDEA Latreille, 1802
PHLOEOCHARINAE Erichson, 1839
PHLOEOCHARIS Mannerheim, 1830
This very widespread and locally common species occurs from lowland to low mountain altitudes throughout Europe and north west Africa, extending north to the UK and the Arctic Circle in Fennoscandia, east into western Russia, and it has recently (2004) been recorded from Halifax, Nova Scotia as an introduction from Europe. In the UK it is widespread though very local and sporadic, occurring north to the Scottish Highlands and Northern Ireland; it is generally absent from The West Country and much of the midlands and most frequently recorded from the south east and Wales. Adults occur year-round, they are active from early spring until the autumn and may also be found during mild winter spells, the typical habitats are all types of woodland where they occur in moss on trees and logs, under bark on standing and fallen timber or among fungi; in the UK it has been recorded from the bracket fungus Daedaleopsis confragrossa (Bolton) J. Schröt. 1888 on Salix and other trees, occasionally from other fungi and from debris under decaying beech and oak bark. On the continent it has been recorded commonly under dry pine bark and in deep layers of decomposing litter, it is locally common in Poland under dead deciduous bark, especially on poplars, and in Italy it occurs under bark and among detritus in deciduous forests at low and middle mountain altitudes. In central Europe it has been recorded from the galleries of various bark beetles including Ips typographus (Linnaeus, 1758), Tomicus piniperda (Linnaeus, 1758) and Xyleborus cryptographus (Ratzeburg, 1837), these last two on Pinus sylvestris L. (Scots pine), where both adults and larvae are thought to be predatory. In Canada it has been recorded from a wide range of deciduous and coniferous trees and associated scolytid galleries. Because of their small size and cryptic lifestyle adults are infrequently recorded, the best ways to find them are by sieving likely material or taking samples for extraction.
Phloeocharis subtilissima 1
© Lech Borowiec http://www.cassidae.uni.wroc.pl/Colpolon/index.htm
Phloeocharis subtilissima 2
© U.Schmidt https://www.kaefer-der-welt.de/index.htm
1.5-2.0mm. Elongate and somewhat fusiform in appearance, very convex and discontinuous in outline with the pronotal and elytral base narrowed and the head much narrower than the pronotum. Dark brown with the elytra partly reddish, often extensively so, and the apical and lateral margins of the abdominal tergites pale, entire dorsal surface with dense pale pubescence, appendages pale to dark brown. Head transverse with convex and prominent coarsely-faceted eyes, vertex finely and densely punctured and clypeus produced beyond the antennal insertions, labrum smoothly curved anteriorly. Antennae indistinctly clubbed; the 2 basal segments longer and broader than the rest, 3 elongate, 4-7 quadrate, 8 slightly transverse and 9-11 a little broader. Pronotum broadest about the middle and smoothly rounded laterally, posterior angles distinct but, from above, the anterior margin appears continuously curved without angles, surface smoothly convex and finely and densely punctured. Elytra transverse and almost parallel-sided, in most specimens a little narrower than the pronotum, surface finely punctured though less densely so than the pronotum, without striae or larger punctures. Elytra strongly bordered, the tergites finely punctured and without basal depressions or ridges. The small size, distinctive habitus and dense pubescence should serve to identify the species; the 5-segmented tarsi and strongly developed posterior trochanters are diagnostic but very difficult to appreciate.
PHLOEOCHARINAE Erichson, 1839
This is a small subfamily of about 55 species in 7 genera; it is widely distributed throughout the New World, Palaearctic, Oceanic and Australian regions although only the single genus Phloeocharis Mannerheim, 1830 occurs in Europe including the UK. The monotypic genera Vicelva Moore & Legner, 1973 and Dytoscotes Smetana & Campbell, 1980 are Nearctic while the New World genus Ecbletus Sharp, 1887 includes 2 species and extends south into Central America. Charhyphus Sharp, 1887 includes 5 species and occurs throughout the New World and a single species is recorded from Russia. The monotypic genus Phloeognathus Steel, 1953 is restricted to New Zealand and the 6 species of Pseudophloeocharis Steel, 1950 occur in Australia with one extending to New Zealand. Phloeocharis Mannerheim, 1830 includes 37 species and is most diverse around the Mediterranean; a single species occurs in the western United States and the remainder occur in southern and central Europe (28 species) and across North Africa with western parts being particularly rich in species. Many species are of restricted distribution, France and Spain are rich in species and some are endemic to islands but only a single and very widespread species, P. subtilissima Mannerheim, 1830, occurs in much of Central Europe and extends north to the UK. Adults generally occur among leaf-litter or in the soil beneath, especially in wooded habitats, and the structure of both adults and larvae mouthparts suggests a predatory way of life.
All species are small, rather parallel-sided and somewhat cylindrical, most are drab black or brown or with contrasting elytra and most are finely and densely pubescent. Members may be recognized by the following combination of characters. Antennae 11-segmented and inserted laterally outside the base of the mandibles, the insertions mostly hidden from above, gradually thickened towards the apex; the last 3 segments forming at best an indistinct club. Temples absent or very short, vertex without ocelli or distinct depressions. (The hypopharynx is unique in shape among the staphs) Pronotum simply convex, without structure. Abdomen with strongly raised lateral margins; tergites 4 and 5 have a pair of circular ‘combs’. Front coxae without a mesal groove, posterior trochanters strongly developed, about a third the length of the coxae. Tarsi 5-segmented. Very similar to various Aleocharinae but distinguished by the lateral antennae insertions, from small Oxytelinae by the 5-segmented tarsi and the form of the hind trochanters and from Omaliinae by the absence of ocelli. The habitus is also suggestive of Tachyporinae but the small size, dense dorsal pubescence and strongly raised abdominal margins are distinctive.