Bolitochara Mannerheim, 1830
This genus of small rove beetles is included within Bolitocharina Thomson, C.G., 1859, a subtribe of the Homalotini Heer, 1839, which is included in the subfamily Aleocharinae Fleming, 1821. As with many of the aleocharine genera, the world faunas remain poorly understood but the present genus is very probably confined to the Palaearctic region with the greatest diversity in the west. Only six species are generally widespread; B. bella Märkel, 1844, B. mulsanti Sharp, 1875, B. obliqua Erichson, 1837, B. pulchra (Gravenhorst, 1806), B. tecta Assing, 2014 and B. lucida (Gravenhorst, 1802) and all but the last of these extend north into the UK. Three are widespread in the Mediterranean region; B. humeralis Lucas, 1846, B. schusteri Bernhauer, 1908 and B. varia Erichson, 1839 while the rest are limited to particular regions. B. anatolica Assing, 2014, B. recta Assing, 2014 and B. lauferi Bernhauer, 1908 are endemic to Turkey, B. smetana Pace, 1989 from Nepal, B. niticeps Assing, 2014 from Azerbaijan, B. persica Assing, 2014 from Iran and B. tenuicollis Assing, 2014 from the Caucasus. Four species are known only from the Far East; B. lobata Sawanda, 1970 and B. varipes Sharp, 1888 from Japan, B. sinica Pace, 2010 from China and B. taiwanensis Pace, 2008 from Taiwan.
Members of the genus have a 4-4-5 tarsal formula, these being surprisingly easy to count at high magnification. Among our other genera with a similar tarsal formula they may be identified by the long and curved temples and broad neck, only slightly transverse pronotum which is distinctly narrower than the rugosely and strongly punctured elytra, and long, parallel-sided or only slightly dilated abdomen. The genus can be generally described as follows. 2.5-5.0 mm. Elongate with broad elytra, long and slender legs and antennae slightly too distinctly thickened from the third segment. Dorsal surface finely pubescent throughout, colour variable but usually with the head dark, pronotum pale to dark brown, elytra pale with dark markings, usually around the scutellum and towards the posterior angles, abdomen pale brown with several contrasting darker segments, usually towards the apex, antennae pale to mid-brown, often
Bolitochara obliqua 1
Bolitochara tecta 1
Bolitochara bella 1
Bolitochara pulchra 1
Bolitochara mulsanti 1
© Lech Borowiec
Bolitochara obliqua 2
Bolitochara bella 2
Bolitochara tecta 2
with the terminal segment and several basal segments paler, palps and legs pale to dark brown. Head rather flat between large convex eyes that are continuous in outline with the temples, clypeus narrowed and produced in front of the antennal insertions, surface smooth, finely punctured and without structure. Temples smoothly curved, often giving the basal half of the head a semi-circular outline, and sometimes finely bordered ventrally. Maxillary palpi well developed, second segment long and slender, third segment broad; expanded from the base to an almost truncate apex, terminal segment elongate and slender. Antennae inserted laterally, near the outer margin of the mandibles, three basal segments long and slender, 4-10 variable; quadrate to strongly transverse, club elongate and pointed. Neck always present but often partially retracted into the thorax. Pronotum broader than the head although sometimes only slightly so, transverse, rounded anteriorly and parallel-sided or converging to perpendicular or obtuse posterior angles, basal margin sinuate and finely bordered, lateral margin finely bordered, surface weakly and evenly convex, without structure, and usually finely punctured throughout. Scutellum transverse, triangular and pointed. Elytra broader and longer than the pronotum, weakly curved or dilated laterally from rounded shoulders to acute and slightly projecting posterior angles, basal margin rather strongly sinuate, sutural margin straight and finely bordered, surface weakly convex and strongly punctured throughout, in some species sexually dimorphic; males having a raised keel near the suture. Abdomen long and strongly bordered, the four basal tergites impressed across the base, the fifth with a raised and almost impunctate basal border and the sixth smoothly convex, all tergites finely punctured, usually more strongly and densely so across the base. Males of some species have a raised median keel on the seventh, and also sometimes on the eighth tergite. Front and hind coxae almost touching, middle coxae more widely separated, front and middle trochanters normal, hind trochanters enlarged. Femora unarmed, long and only weakly thickened from the base. Tibiae slender throughout, without external bristles or teeth and each with a tiny apical spur. Tarsi slender in both sexes; basal hind tarsomere as long as the next two combined.
Our species are very distinctive and because several are generally common they will soon become familiar, at least to the generic level, even in the field. Males may usually be distinguished on morphological features but females often need to be identified by comparison or association. Dissection is rarely necessary but will decide the identity of doubtful males (and females of obliqua and bella), see HERE.
Head less strongly rounded to the base, neck short (often hidden) and broader where it meets the temples; more than half the width of the head measured across the eyes. (Males with or without a raised keel beside the elytral suture, seventh abdominal tergite with or without a median keel.)
Head more strongly rounded to the base, neck appearing longer and more distinct but narrower where it meets the temples; about half the width of the head measured across the eyes. (Males with a raised keel by the elytral suture and on the seventh and eighth tergite.)
Seventh tergite in males with granular microsculpture (appearing as numerous small tubercles at high magnification), but lacking a median keel. Elytra unmodified. [Head and pronotum dark brown, sometimes black, densely punctured and clearly microsculptured. Temples finely bordered ventrally. Elytra extensively darkened around the scutellum and hind angles, often with a striking reddish oblique stripe from the shoulders to the sutural angle. Abdomen extensively dark or with the margins of some tergites reddish. Antennae dark brown with two or three basal segments pale, antennomeres 6-10 strongly transverse. Legs brown, often with darkened femora.]
Seventh tergite in males with a median keel. Elytra with or without a sutural keel.
Head matt, densely and rather strongly punctured, the distance between the punctures smaller than the puncture diameter. Temples finely bordered ventrally. Elytra more transverse and less than 1.1X longer than the pronotum, smoothly convex. Males with a raised keel adjacent to the elytral suture. Antennae rather short, with segments 6-10 strongly transverse. [Head dark, pronotum orange to dark brown, elytra pale with scutellary and outer angles darkened, sometimes extensively so, abdomen pale with at least some distal segments darkened. Legs pale, antennae dark with the terminal and several basal segments pale.)
Head shiny, less strongly and densely punctured, about the same as the pronotum. Temples simple. Elytra less transverse and about 1.1X longer than the pronotum, surface distinctly raised before an oblique impression from the shoulders to the sutural margin, sutural margin not raised. Appendages more elongate, antennomeres 6-10 less strongly transverse. [Head and pronotum concolorous pale to dark brown, elytra and abdomen as in bella but often paler. Legs pale brown, antennae brown with the terminal and several basal segments pale.]
Head dark and strongly contrasting with the orange or brown pronotum. Width across the neck constriction slightly greater than half the head width. Antennomeres 9 and 10 more transverse. Forebody more finely punctured, elytra smoothly flattened dorsally, less strongly and closely sculptured. [Elytra often extensively dark below the shoulders.] Abdomen pale with at least one subapical tergite darkened.] On average smaller, 3.5-4.5 mm.
Head and pronotum more or less concolorous reddish brown to dark brown. Width across the neck constriction about half the head width. Antennomeres 9 and 10 less transverse. Forebody more strongly punctured. Elytra obliquely depressed from the shoulder to the sutural angle, more strongly and closely sculptured. [Elytra usually with a distinctly contrasting pale band from the shoulders to the sutural angle, apical margin often narrowly pale. Abdomen with at least one dark subapical segment, basal tergites often darkened across the base or the middle.] On average larger, 4.0-5.0 mm.
All species are associated with decaying trees, fallen timber and leaf litter in deciduous woodland and wooded parkland etc, less often in mixed or conifer woodland. They are often associated with sporocarps or masses of sub-cortical mycelia although adults sometimes occur under dry bark devoid of fungi. Adults rarely occur on the surface and are most easily sampled by tapping fungi over a sheet, especially old and decaying specimens, or by breaking apart terrestrial fungi, they rarely occur in large numbers and several species may occur together. Both adults and larvae are fungivores and larvae have also been observed feeding on dead insects and sub-cortical detritus. Adults may be found throughout the year; they are often active in the winter and they peak in abundance during late spring and early summer. Many species have suffered a drastic Europe-wide decline over the 20th century.
B. bella is locally common across southern and central England as far north as the Humber, and there are only occasional and sporadic records from Wales and the West Country. It is usually associated with large fleshy fungi on dead or decaying deciduous trees, often in damp woodland or old trees in parkland etc.
B. mulsanti is a very rare species in Europe as well as the UK; there are a few widely scattered records from England and Wales and it has been recorded from the Scottish Highlands-although this last record remains unconfirmed. The species occurs among fungoid decaying wood on various deciduous trees as well as Pine, and has been recorded from Birch polypore (Fomitopsis betulina (Bull)) developing on decaying birch.
B. obliqua is generally common throughout England and Wales although less so in the north and generally absent from the West Country, and there are records from the Scottish Highlands, the Western Isles and Northern Ireland. Adults occur under bark and among decaying wood on trees and fallen timber, and both adults and larvae are particularly associated with the bracket fungus Trametes versicolor (L.) Lloyd (1920).
B. pulchra is another very rare species, both in the UK and across Europe generally; here it is known from North Wales and there are a few widely scattered records from England although these remain unconfirmed. Adults have been found in Birch polypore fungus (Fomitopsis betulina (Bull)), under bark on decaying Beech trees (Fagus L.) and in decaying wood.
B. tecta With the general exception of the West Country, this species is widespread though rather local across England and Wales and much more local and scarce further north into southern Scotland and in the West Country. Adults occur among fleshy sporocarps developing on old and well decayed stumps and trunks.