Pseudopsis sulcata Newman, 1834
This is the only widespread European member of the genus and the only one to occur here; it is present throughout Europe north to the Baltic coast and the UK, extending into Russia, Asia Minor and northwest Africa and has been recorded from Central America. Through most of the European range it is a very rare beetle with only very few or single records from many countries e.g. Poland, Germany and Czech Republic, it occurs mostly at mountain altitudes, between 900 and 1900m, but there are records from disturbed lowland areas where it occurs among straw and leaf-litter etc. on arable field margins, meadows and in deciduous and mixed woodlands, mostly between October and March. Adults occur very sporadically and are rarely found at one site for long. While still very local and rare the species seems to be more common in the UK than in Central Europe and there are records scattered across England although it seems to be absent from The West Country and there is a single record from North Wales; Joy (1932) states that it is rare in vegetable refuse while Tottenham (RES Handbook, 1954) states ‘In stack refuse; not common, very local; England, Ireland’. Adults may be recorded by sifting decaying straw, moss and leaf-litter, they are thought to have good dispersal abilities and should, in theory, be caught in flight-interception traps or attracted to light.
2.5-4.0mm. Body pale to dark brown, usually with the head darker and the appendages paler. Head with a longitudinal ridge between small and weakly convex eyes, temples long and converging towards the base but usually mostly retracted into the prothorax, clypeus weakly rounded anteriorly, and mandibles with several large internal teeth. Antennae inserted on the anterior margin outside the base of the mandibles, basal segment long and broad, 2-11 gradually broadened to an indistinct club. Pronotum transverse, rounded laterally to distinct anterior angles and rounded posterior angles, surface densely punctured and with four strongly-raised longitudinal ridges. Elytra transverse with rounded shoulders and a straight apical margin, strongly and densely punctured and each with two strong longitudinal ridges. Abdominal tergites with an oblique impression from near the middle of the base towards the apex, each with a short and curved seta at the apical angle.
PSEUDOPSINAE Ganglbauer, 1895
Historically this small group included only the single genus Pseudopsis Newman, 1834, and while the limits and even the placement of the subfamily within the Staphylinidae are still far from certain, it is now generally accepted to include 4 genera and about 35 species. The majority of species, about 50, are included in Pseudopsis; this is the only widespread genus and is represented in the Holarctic, Oriental, Neotropical and Australasian regions. Nanobius Herman, 1977 includes the single species N. serricollis (LeConte, 1875) from western North America. Asemobius Horn, 1895 and Zalobius LeConte, 1874 both include 2 species and are restricted to western North America. The Nearctic fauna includes 8 species of Pseudopsis, 5 have been recorded from the Neotropical region and a single species, P. arrowi Bernhauer, 1939 occurs in New Zealand, 2 occur in Europe and the remainder occur in the eastern Palaearctic and northern Oriental regions. Of the European species one, P. cypria Zerche, 1992, is endemic to Cyprus while P. sulcata Newman, 1834 is widespread and extends into Asia and Mediterranean North Africa.
Little is known of the biology of the group and larval stages are largely unknown, most species occur among litter in temperate wooded areas although Zalobius and Asemobius are associated with wet moss and flood refuse by small mountain streams. Pseudopsis occur among litter and decaying vegetation but have also been recorded from mammal nests, mouldy pine-cones, dung and decaying fungi, and adults are sometimes swept from dry vegetation in warm weather. The feeding habitas are not known but gut-content analyses show a lack of fungal spores or organic detritus etc. typical of saprophagous species and the structure of the mouthparts suggests a predatory way of life.
Members of the Pseudopsinae are distinguished from other staphylinid groups by the abdominal morphology, in both sexes the ninth tergite is fused dorsally and has a stridulatory file on each side, more practically they may be recognized by the 11-segmented antennae which lack a club, coarsely punctured head and pronotum and longitudinal costae or carinae to the pronotum and elytra and sometimes also the head. So far as our UK fauna is concerned the only confusion might be with species of Micropeplus Latreille, 1809 but these are distinctive due to (among other things) the clubbed antennae. All species are small, 1.8-7.0mm, they have a distinctive appearance and the majority should be recognized from a familiarity with our single UK species (see below). Body broad and flattened, most are entirely brown or reddish brown and lack any metallic reflection, and apart from the usual sensory setae are only very finely pubescent. All body parts are generally distinctive, the head is quadrate to widely transverse with convex eyes and distinct temples, the dorsal surface is variously impressed and in some with raised carinae, the mandibles are often produced and prominent and the labrum is truncate or sinuate anteriorly. Antennae relatively short, the basal segment long and much broader than the rest, 2-8 elongate to transverse, 9-11 broader and often transverse, forming a weak, elongate and poorly-delimited club. Pronotum very variable but usually transverse and sometimes very widely so, lateral margins simply rounded or variously toothed, in Zalobius with a strong lateral tooth and strongly narrowed to a short basal margin, dorsal longitudinal carinae always present, procoxae transverse and convex, closely approximated but usually with a carinate or spiniform process between. Mesosternum sometimes carinate, mesocoxae transverse and either narrowly separated by meso- and meta-sternal processes or contiguous, metacoxae transverse and contiguous. Scutellum always visible. Elytra transverse with rounded shoulders and parallel or rounded lateral margins, basal margin straight, sinuate or emarginate, lateral epipleural ridge and longitudinal dorsal carinae always present. Abdomen long and tapering, the segments transverse and strongly raised laterally, basal segments usually with a wide oblique line from near the middle of the base to the lateral impression, usually with a strong seta at the posterior angles, surface densely punctured and very finely pubescent. .Legs short and slender with femora substantially visible from above, tibiae smooth or with longitudinal series of spines, terminal spurs small but distinct. Tarsi 5-segmented (3-segmented only in the Nearctic Pseudopsis minuta Fall, 1901), basal segments short and often transverse, the terminal segment longer, claws small, curved and smooth with a bisetose empodium between. Pseudopsis may be distinguished by the form of the maxillary palpi, here the terminal segment is diminutive and less than a third of the width of the penultimate segment while in the other genera it is about the same width.