Bolitobius Leach, 1819
Parabolitobius Li, Zhao & Sakai, 2000
These genera form a distinctive group within the Tachyporinae by virtue of the size, the well-developed terminal maxillary palpomere and the proportionally long third antennomere when compared with the second. They are relatively large for Tachyporinae, 6-9mm, colourful and very distinctive in habitus; Parabolitobius was formerly included in Bolitobius. The following brief description applies to the three UK species. Head black and shiny, with only a few scattered sensory bristles, eyes weakly convex and protruding, temples short and near-parallel, mostly retracted into the pronotum, clypeus weakly produced forward and rather strongly narrowed. Mouthparts pale, terminal segment of maxillary palps short but as wide across the base as the apex of the penultimate segment. Antennae narrow and moderately long, reaching back onto the elytra, basal segment long, curved and gradually widened to the apex, second segment much shorter than the first and third, fourth to tenth segments becoming less elongate, terminal segment much longer than the penultimate in Bolitobius, only slightly longer in Parabolitobius. Pronotum widest towards the base and narrowed to distinct anterior angles, basal and lateral margins form a smooth curve, surface convex and shiny, with only a few scattered setiferous punctures, generally close to the margins. Elytra short and near-parallel, finely bordered laterally and with rather strongly-bordered sutural margin and obliquely-truncate or separately-rounded posterior margins. Basal width narrower than the base of the pronotum, shoulders well-developed but generally hidden beneath the pronotal base. Abdomen distinctly tapered to the apex, least so in Parabolitobius, with only weakly-raised lateral margins, tergites strongly punctured throughout in Parabolitobius, mostly towards the base on Bolitobius. Legs long, slender and entirely pale. Front femora short and usually hidden beneath the pronotum, the tibiae smooth and gradually broadened to a rounded apex with a strong internal spine. Mid- and hind femora long, slender and substantially visible from above, the tibiae gradually thickened to the apex, with several long setae along the internal and external margins and long stout spurs on the inner apical angles. Front tarsi relatively short with the terminal segment long and slender, middle and hind tarsi thin and very long; the basal segment longest. Claws short and curved, smooth and at most angled or weakly toothed at the base. Males have wider basal pro-tarsal segments and a longer terminal antennal segment.
This species occurs throughout most of Europe with the exception of the far north of Fennoscandia, it is generally common in southern and western regions and more sporadic further north where there seems to have been a long –term decline since the nineteenth century. Here it occurs sporadically north to the Scottish Highlands; it is locally common in the southeast, East Anglia, the midlands and around the Scottish Borders but either absent or very rare elsewhere. Adults occur year-round, peaking in the spring and autumn, they occur among decaying vegetation and fungi in open woodland and wooded borders, agricultural land and parkland. We have found them among decaying terrestrial fungi in the autumn and extracted them from grass tussocks from agricultural headlands in the winter. Adults may be recorded by pitfall-trapping or sieving suitable samples over a sheet.
Bolitobius is a Holarctic genus of about 30 described species, the greatest diversity is in the Palaearctic region but only three species occur in central Europe; boreomontanicus Schülke, 2010, sometimes considered as a subspecies of the following, is a rare mountain species extending north to the Baltic States but not the UK while B. castaneus (Stephens, 1832) and B. cingulatus Mannerheim, 1830 are locally common and much more widespread, the latter being Holarctic, and extend north into the UK. Of the ten Palaearctic species of Parabolitobius only two occur in central Europe, both are widespread though generally rare but only P. inclinans (Gravenhorst, 1806) extends north to the UK. Our three species are easily identified as follows:
-6.5-7.5mm. Elytra strongly and quite densely punctured throughout. Pronotum and elytra pale, first and last antennomeres pale, abdominal tergites more extensively punctured.
-6-9mm. Each elytron with several longitudinal series of fine punctures; one next to the suture, two or three on the disc and one by the lateral margin, each consisting of four to ten punctures. Pronotum black (rarely pale, see next couplet), at least two basal antennomeres pale, abdominal tergites strongly punctured only across the base.
-Larger, 7-9mm. Antennae with two basal segments and the terminal segment pale, and the penultimate segment at least partly pale. Sutural row with 5-6 punctures. Abdominal apex extensively pale. Male with a broad longitudinal series of short setae on the apical half of the sixth sternite.
-Smaller, 6-7mm. Antennae with at least three basal segments and the terminal segment pale, the penultimate segment dark. Sutural row with 8-10 punctures. Terminal abdominal tergite dark. Male with a narrow longitudinal series of short setae on the apical half of the sixth sternite. In the rare var. merdarius Gyllenhal the pronotum is red.
B. castaneus (Stephens, 1832)
B. cingulatus (Mannerheim, 1830)
With the exception of the Iberian and Balkan Peninsulas, this species occurs throughout Europe extending north to the UK and beyond the Arctic Circle in Scandinavia. It is generally the most common member of the genus, occurring from lowlands to low mountain regions in a variety of damp and sheltered habitats; in lowlands mostly among moss, fungi or decaying litter in deciduous forests or wooded parkland but at higher altitudes under rocks and debris in open situations. Here it is more common and widespread than the previous species, occurring throughout England and Wales although generally absent from the West Country, and extending north to the Scottish Highlands and Outer Hebrides. Adults occur year-round, they may be found under logs or bark etc. by day and we have found them active on fungi at night.
P. inclinans (Gravenhorst, 1806)
This is a generally rare species of southern and central Europe (sometimes described as pontomediterranean) extending sporadically north to the Baltic countries and the UK where it widespread though very local and sporadic north to the Scottish Highlands. It is usually associated with decaying litter, moss or damp decaying wood from lowlands to the subalpine zone although at higher altitudes it also occurs among moss or under stones in more open situations.