Pselaphus heisei Herbst, 1791
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POLYPHAGA Emery, 1886
STAPHYLINOIDEA Latreille, 1802
PSELAPHINI Latreille, 1802
Pselaphus Herbst, 1791
A locally common species throughout most of Europe from Spain to the Black Sea and north to the UK and the Arctic Circle in Scandinavia, it is generally absent from Italy and the Balkan Peninsula although it is present on Corsica, there are also records from the eastern Palaearctic region but it is not known whether this distribution is continuous. Several subspecies are known from Mediterranean regions. In the UK it is locally common throughout England with the exception of the West Country, rather more common across Wales, and there are scattered records to the north of Scotland, including the Western Isles, and in the north of Ireland. Adults occur year-round, they overwinter among moss or in tussocks etc. and become active in March or April, peaking in abundance from May until July and becoming scarce during the warmer parts of summer. Typical habitats are well-vegetated wetland margins and peat bogs etc. but they also occur on permanently wet floodplain grassland and wooded borders; adults spend most of their time among moss or under decaying plant debris but they occasionally climb stems and may sometimes be found on leaved during the day. Little is known of the biology but larvae are thought to be carnivores and adults have been observed capturing and feeding upon small mites and springtails. Adults may be found by sieving or extracting suitable samples, in the collecting tray they begin to move after a while and may be seen walking slowly while rapidly tapping the tray with their antennae and maxillary palps, this is probably hunting behaviour, maybe trying to detect chemical signals from prey. They capture prey items readily and may take some considerable time manipulating and consuming them, here the antennae and palps are held out laterally and neither is involved with feeding; unlike some other members of the subfamily the palps are not furnished with adhesive setae or surfaces and so are probably not involved with prey capture. Kept out of strong light adults may be observed feeding in the collecting tray, this is a protracted process but is readily abandoned if another prey item is presented. On rare occasions, especially during the spring and early summer, adults may occur in numbers but more generally they will be found as single specimens or pairs.
1.3-1.9 mm. Readily recognized on general habitus and the form of the pronotum and palps, forebody long and slender, elytra broad and truncate, dorsal surface shiny brown with sparse pale pubescence. Head with various depressions and two patches of dense recumbent pubescence between protruding and coarsely-faceted eyes, temples curved and converging to a narrow neck, clypeus with a deep median furrow and produced and parallel-sided in the form of a rostrum. Maxillary palps inserted laterally behind the antennae and much longer than half the antennal length, basal segment long, sinuate and abruptly widened before the apex, second segment short and globular, the (apparently) terminal segment narrow from the base and then with a long, rounded club, the surface with several rows of small dark tubercles. Antennae inserted on proximate apical tubercles, 11-segmented with a 2-segmented club. Pronotum elongate, broadest about the middle and narrowed to obtuse and rounded angles, surface smoothly convex, without furrows or basal impressions. Elytra curved and expanded from a narrow base to broadly-truncate and densely pubescent apical margins, without basal impressions but with an impressed sutural stria and one or two fine longitudinal lines on the disc. Abdomen substantially exposed; the widest part of the basal tergite about as wide as the widest part of the elytra. Male with the metasternum raised either side of a deep groove and the basal sternite with a wide median depression. Legs long and slender with clavate femora and narrow tibiae, tarsi with three simple segments although the basal segment is diminutive and may be difficult to see, and all with a single smooth claw. Several other UK members of the subfamily are broadly similar and have long maxillary palps but the present species is unique in having a long and comparatively narrow club towards the end of the apical segment, this club is not grooved and has rows of small dark tubercles.