Bulirschius Borovec, 2025

Borovec, Roman, 2025, Two new and one enigmatic genus of Oosomini from South Africa with description of seven new species (Coleoptera: Curculionidae: Entiminae), Zootaxa 5642 (2), pp. 101-126 : 105-118

Bulirschius Borovec gen. nov.

http://zoobank.org/ urn:lsid:zoobank.org:act:760C2CCF-9008-447D-80A9-F40CB9BDA76A

Figs (3–7, 15–43)

Type species. Bulirschius tesinskyi Borovec sp. n. by present designation. Gender masculine.

Diagnosis. Small edaphic Oosomini 1.8–3.1 mm long; rostrum in dorsal view wider than long, at base as wide or slightly wider than at apex; epifrons at base narrower than space between anterior margins of eyes, posteriorly separated from head by moderately wide transverse furrow with ill-defined margins; frons glabrous; antennal sockets dorsally placed, pit-shaped to reniform, in lateral view not reaching eyes; scape at most as wide as club; metatibia with apical surface glabrous and with setose bevel; claws free, divaricate; ventrite 1 at middle as long as ventrites 2–4 combined, ventrite 2 slightly shorter than ventrites 3 and 4 combined; suture between ventrites 1 and 2 straight; female sternite VIII with apodeme terminating inside of plate, plate umbrella-shaped with membranous basal margin.

Description. Body length 1.75–3.09 mm. Ground colour of body ( Figs 3–7 ) dark brownish to blackish, basal part of scapes, funicles with clubs and tarsi paler, reddish brown. Vestiture of body consisting of very dense appressed scales of different shape, completely hidden integument, only in one species appressed scales somewhat sparse; antennal scapes and legs with similar, but slightly smaller scales; funicles with tarsi sparsely setose, clubs finely densely setose; underside densely or sparsely scaled, abdominal ventrites in several species glabrous. Elytra with one regular row of dense, semi-appressed, subspatulate, spatulate or clavate scales; pronotum and rostrum with head with irregularly scattered identical setae; scapes with moderately long slender erect setae at inner sides; funicles with erect setae; femora and tibiae with short, semi-appressed to erect slender scales; tarsi setose. Colour pattern of body inconspicuous, light or dark brownish, elytra often marbled with small spots, pronotum with 2–3 longitudinal stripes, only in one species appressed scales with green sheen.

Rostrum ( Figs 15–24 ) robust, 1.04–1.40× as wide as long, in dorsal view with concave or straight sides, at apical portion rounded around scrobes, here as wide, exceptionally slightly wider than at base; in lateral view regularly vaulted. Epifrons narrow to wide, at base 0.5–0.7× as wide as rostrum in respective part, mostly with slightly concave sides, at base narrower than space between anterior margins of eyes, dorsally flat or longitudinally slightly depressed, posteriorly separated from head by shallow to deep transverse furrow, moderately wide, with ill-defined margins, at level between anterior and posterior margins of eyes. Epifrons under scales solidly laterally carinated, medially in some species with shallow longitudinal furrow. Frons short to long, glabrous, deepened, posteriorly not carinated, with 4 pairs of fine and long apical setae. Epistome short, U-shaped, posteriorly carinate. Antennal sockets in dorsal view well visible in anterior half of rostrum, pit-shaped to reniform; in lateral view short, placed near dorsal margin of rostrum, somewhat enlarging posteriad, slightly curved, with dorsal margin directed towards dorsal margin of eye and ventral margin towards ventral margin of eye, separated from eye by wide squamose stripe. Vertex almost flat, wide. Head very wide, behind eyes short and distinctly enlarged, when cleared of scales with fine longitudinal ridges converging towards base of rostral median groove, giving vertex a lirate appearance, or densely punctured. Eyes moderately small, weakly convex, hardly or slightly prominent from outline of head in dorsal view, in lateral view placed nearer dorsal margin of head, subcircular. Submentum with pair of fine setae. Mandibles with three fine setae, asquamose. Gena and subgena densely squamose. Submentum with a pair of fine setae.

Antennae ( Figs 3–7 ) with scape moderately short and robust, 4.4–6.7× as long as at apex wide, 1.2–1.3× as long as funicle, slightly exceeding anterior margin of pronotum when folded, slightly curved at basal third, evenly enlarging apicad, at apex slightly narrower to as wide as club. Funicle with 7 articles; articles 1 and 2 slender, long, conical, articles 3–7 isodiametric to wider than long. Club narrowly to widely spindle-shaped with article 1 longest, comprising half of club length, less setose and more glabrous than other articles.

Pronotum ( Figs 3–7 ) 1.16–1.78× as wide as long, widest at midlength or slightly behind, with sides rounded, tapering more anteriad than posteriad, behind anterior margin weakly constricted. Disc regularly domed, base slightly arched. Pronotum in lateral view slightly vaulted, flattened behind anterior margin. Anterior margin in lateral view without setae or ocular lobes, directed slightly obliquely ventrad to procoxae. Procoxal cavities contiguous, round, located very near to anterior margin; procoxae subglobular. Scutellar shield dorsally invisible.

Elytra ( Figs 3–7 ) oval to long oval, 1.13–1.37× as long as wide, widest at midlength, only in one species widest at basal quarter, with sides rounded, apically narrowly to broadly rounded, humeral calli missing, in one species with small, dorsally visible posthumeral callus; apex of elytra not visible in dorsal view, hidden by overhanging slope. Elytra 10-striate, striae punctate, interstriae flat. Elytral profile in lateral view almost flat. Mesocoxae semiglobular, mesosternal process about as wide as a quarter of diameter of mesocoxa, reaching half of mesocoxa length. Metacoxae shortly transverse, placed laterally. Mesanepisterna large, squamose, reaching metaventrite; mesepimera narrow. Metanepisterna narrow, separated from metaventrite, with visible suture.

Femora medially somewhat swollen, unarmed. Tibiae short, robust, straight; protibia ( Fig. 25 ) 5.2–6.4× as long as at midlength wide, with lateral side straight, apically obliquely subtruncate or rounded, with fringe of fine, in some species sparse, yellowish to blackish setae, inner portion with brownish mucro; meso- and metatibia with short mucro, in two species metatibia lacking mucro; tibiae in some species finely denticulate at apical inner part, prominences mostly hardly visible with incrustation; apical surface of meso- and metatibia glabrous, outside fringed by fine setae, inside armed with short sparse spines, yellowish to blackish; metatibia with densely setose bevel, not fringed outside. Tarsi slender, tarsomere 1 slightly shorter than tarsomeres 2 and 3 combined; tarsomere 2 transverse; tarsomere 3 deeply bilobed and distinctly wider than the others; onychium 0.9–1.6× as long as tarsomere 3; claws free, weakly divaricate.

Abdominal ventrites ( Figs 26–28 ) short and wide, from 1.1× as long as wide to 1.2× as wide as long, distinctly tapering apicad; ventrite 1 largest, in middle about as long as ventrites 2–4 combined, laterally about 3× longer than ventrite 2; ventrite 2 slightly shorter than ventrites 3 and 4 combined; ventrite 5 in males shorter than 3 and 4 combined, subtrapezoidal, apically obtuse, in females longer than 3 and 4 combined, subtriangular, apically rounded. Sutures straight, suture between ventrite 1 and 2 fine, narrow, the others wide and deep. Ventrites densely squamose with single transverse row of semi-appressed, slender, subspatulate setae, or glabrous with sparse piliform setae. Metaventral process obtuse, narrower than transverse diameter of metacoxa to wide, about 1.5× as wide as transverse diameter of metacoxa.

Male terminalia. Penis ( Figs 29–33 ) moderately small, slender, temones about twice longer than body of penis; endophallus with 2–3 very short to long, irregularly shaped sclerites. Tegmen ( Fig. 34 ) with short slender parameres, distant at their bases, in one species with long parameres connected at base, in one species lacking parameres; manubrium 1.5× as long as diameter of ring. Sternite IX anteriorly curved with slender apical plate, posteriorly with fused basal arms.

Female terminalia. Sternite VIII ( Figs 40–42 ) with medium long to long apodeme, 1.6–3.5× as long as plate, terminating inside of plate, near its apex; plate umbrella-shaped, with membraneous basal margin; gonocoxites ( Fig. 43 ) subtriangular, with long and slender apical styli with tuft of fine setae; spermatheca ( Figs 35–39 ) U-shaped, with developed ramus and collum, differing in shape between species.

Sexual dimorphism. Sexes externally indistinguishable except for slight differences in shape of ventrite 5.

Derivation of name. This genus is dedicated to Petr Bulirsch (Prague, Czech Republic), eminent specialist on Carabidae , mainly the tribe Scaritini Bonelli, 1810 , a good friend of the author, who has participated in 10 field trips to South Africa and provided me with extensive material of sifted broad-nosed weevils.

Biology. All type material was collected by sifting or into pitfall traps in two different types of habitats: two species were collected from litter in indigenous forests, and three species were collected in fynbos or mountain fynbos.

Distribution. The genus is native to the Western Cape of South Africa.

Species included. Five new species described below.

Taxonomic remarks. Bulirschius belongs to the tribe Oosomini based on its free claws, trisetose mandibles, dorsally placed antennal sockets, glabrous frons, lack of ocular lobes and vibrissae on lateral margins of pronotum, lack of laterally protruding humeral elytral calli and the setose bevel of the metatibiae. This genus differs from all other Oosomini in that it includes edaphic species, thus they have characteristics closely connected to a life in forest litter or fynbos soil, such as shortening of extremities, lateral placement of metacoxae with a wide metaventral process between them, and reduced eyes and small body size.

Bulirschius shares free claws and a small body size with members of the tribe Namaini Borovec & Meregalli, 2021 , but it does not belong to this tribe in that the head separated from the rostrum by a shallow, wide, transverse furrow (rostrum posteriorly continuous with head in Namaini ), epifrons at base narrower than space between anterior margins of eyes (epifrons at base reaching inner margins of eyes in Namaini ), frons glabrous (frons densely squamose in Namaini ) and antennal sockets dorsally clearly visible (antennal sockets in dorsal view hardly visible in Namaini ).

Several species of Bulirschius with concave sides of the rostrum resemble several species of the embrithine genus Luciculio Borovec, 2022 , a genus known from north-eastern South Africa, in the provinces of Limpopo, Mpumalanga and Eastern Cape and Eswatini. Both genera share the following characters: rostrum separated from head by shallow transverse sulcus, glabrous frons, antennal sockets fully dorsally placed and apical surface of metatibiae glabrous. Both genera are possible to distinguish by the metatibiae with setose bevel in Bulirschius (metatibiae with squamose corbel in Luciculio ), tibiae mucronate in Bulirschius (at least in females with mucro and premucro in Luciculio ), free claws in Bulirschius (free or connate in Luciculio ).

Bulirschius resembles the embrithine genus Glyptosomus Schoenherr, 1847 , of which 11 species are described and another at least 80 or more are undescribed, deposited in various collections. Both genera share small body size, densely squamose body, rostrum short and wide, elytral interstriae with dense row of short, subspatulate setae and in one Bulirschius species with dorsally visible, laterally prominent subhumeral bumps. Glyptosomus is known from the north-eastern part of the southern part of Africa, i.e., South Africa (provinces Eastern Cape, KwaZulu-Natal, Gauteng, Limpopo, Mpumalanga), Mozambique and Zimbabwe. Bulirschius can be easily distinguished from this genus by claws free (connate in Glyptosomus ), metatibiae with setose bevel (squamose corbel in Glyptosomus ), frons glabrous (squamose in Glyptosomus ), rostrum separated from head by wide, shallow transverse furrow with ill-defined margins (separated by narrow, well-edged transverse sulcus in Glyptosomus ), apical surface of metatibiae glabrous (squamose in Glyptosomus ) and tegmen with short parameres (lacking parameres in Glyptosomus ).

Within Oosomini , Bulirschius is easily distinguishable from other known genera by a rostrum wider than long, small, laterally placed eyes, short and robust antennal scapes, small body size and densely scaled dorsal body parts. Bulirschius is most similar to Basothorhynchus Borovec, 2019 , another genus with an edaphic way of life. Both genera share all the characters stated above, except for the densely scaled body which is glabrous or very sparsely scaled in Basothorhynchus . It is possible to distinguish Bulirschius from Basothorhynchus by the following characters: Bulirschius : All femora edentate; epifrons at base narrower than space between anterior margins of eyes; rostrum posteriorly separated from head by transverse furrow; ventral margin of rostrum in lateral view distinctly shorter than thickness of rostrum at its base; slope of elytral declivity distinctly overhanging apices of elytra in dorsal view; ventrite 1 in middle about as long as ventrites 2–4 combined; female sternite VIII with apodeme distinctly longer than small plate. Basothorhynchus : Femora with tooth; base of epifrons as wide as space between anterior margins of eyes; rostrum posteriorly continuous with head; ventral margin of rostrum in lateral view as long as thickness of rostrum at its base; slope of elytral declivity hardly overhanging apices of elytra in dorsal view; ventrite 1 in middle distinctly shorter than ventrites 2–4 combined; female sternite VIII with apodeme subequal in length with large plate.

A key to Oosomini genera containing species with a terricolous life style and smaller than 3.50 mm, including Bulirschius , is given below in the description of the other new genus of Oosomini .

Remarks about intrageneric variability. The genus is well defined by the characters stated above, which allow it to be separated from other genera of Oosomini . Some characters vary within Bulirschius : abdominal ventrites are either densely squamose (2 species) or glabrous, sparsely covered by piliform setae (3 species); metaventral process is distinctly wider than transverse diameter of metacoxa (3 species) or slightly narrower than its diameter (2 species); two species have metatibiae without mucro, while others have metatibiae with long mucro; all species have tegmen with short, inconspicuous parameres, while one species has long parameres connected at the base and one species has the ring of tegmen lacking parameres; one species has plate of female sternite VIII with longitudinal sclerites, while all other species have plates without sclerites. Future research on additional new species can help determine if these differences allow for the placement of these species in two different genera.

Key to Bulirschius species

1. Appressed scales on dorsal part of body sparse, not covering integument; on elytra shallowly, on pronotum and head with rostrum deeply bifid, their emargination reaching half of scale length. Appressed scales form greenish spots with metallic sheen. Erect setae long, clavate, distinctly prominent from outline of elytra and pronotum in dorsal view. Body size 2.1–2.6 mm .................................................................... B. dyssomatiformis Borovec , sp. nov.

- Appressed scales on dorsal part of body dense, fully covering integument; regularly rounded or oval, not bifid. Appressed scales brownish without metallic sheen. Erect setae short, subspatulate or spatulate, not prominent from outline of elytra and pronotum in dorsal view......................................................................................... 2

2. Elytra widest at basal quarter with laterally prominent subhumeral bumps, visible in dorsal view. Rostrum in apical portion slightly wider than at base. Antennal scapes with tip subequal in width with clubs. Body size 2.2–3.1 mm ............................................................................................. B. tesinskyi Borovec , sp. nov.

- Elytra widest at midlength, lacking subhumeral bumps. Rostrum in apical portion as wide as at base. Antennal scapes with tip narrower than clubs.................................................................................... 3

3. Rostrum slender, 1.04–1.09× as wide as long, with distinctly concave sides. Eyes not prominent from outline of head. Elytra elongate, at least 1.32× as long as wide. Metaventral process 1.5× as wide as transverse diameter of metacoxa. Spermatheca with ramus and collum subparallel to each other, subequal in length. Body size 1.8–2.5 mm .... B. ruiterbos Borovec , sp. nov.

- Rostrum wider, at least 1.31× as wide as long, subparallel-sided with straight sides. Eyes prominent from outline of head. Elytra wider, at most 1.32× as long as wide. Metaventral process narrower than transverse diameter of metacoxa. Spermatheca with ramus perpendicular to distinctly longer collum............................................................. 4

4. Body wide, pronotum 1.7–1.8× as wide as long, elytra oval, at most 1.16× as long as wide. Semi-erect elytral setae densely placed in rows, distance between them shorter than length of one seta. Furrow between head and rostrum at level of anterior eyes margins. Abdominal ventrites glabrous. Onychium longer than tarsomere 3. Plate of female sternite VIII lacking sclerites. Body size 1.9–2.8 mm .......................................................... B. densatus Borovec , sp. nov.

- Body narrow, pronotum 1.1–1.2× as wide as long, elytra long oval, at least 1.28× as long as wide. Semi-erect elytral setae sparsely placed in rows, distance between them at least 3× as long as length of one seta. Furrow between head and rostrum at level of posterior eyes margins. Abdominal ventrites squamose. Onychium shorter than tarsomere 3. Plate of female sternite VIII with longitudinal sclerites. Body size 1.9–2.2 mm .............................. B. inconspicuus Borovec , sp. nov.

Figures

FIGURES 1–4. Dorsal habitus. 1. Andringitrabius polymitus. 2. Holotype labels of Andringitrabius. 3. Bulirschius densatus. 4. B. dysommatiformis. Not to scale.

FIGURES 5–8. 5–7: Dorsal habitus. 5. Bulirschius inconspicuus 6. B. ruiterbos. 7. B. tesinskyi. 8: Ventral habitus. 8. Kostalius rotundisetis. Not to scale.

FIGURES 13–24. 13–24: Head including rostrum in dorsal and lateral view. 13, 14. Andringitrabius polymitus. 15, 16. Bulirschius densatus. 17, 18. B. dysommatiformis. 19, 20. B. inconspicuus. 21, 22. B. ruiterbos. 23, 24. B. tesinskyi. Scale 0.50 mm.

FIGURES 25–43. 25: Right protibia. Bulirschius tesinskyi. 26–28: Abdominal ventrites. 26. B. densatus. 27. B. ruiterbos. 28. B. tesinskyi. 29–33: Penis in dorsal view. 29. B. densatus. 30. B. dysommatiformis. 31. B. inconspicuus. 32. B. ruiterbos. 33. B. tesinskyi. 34: Tegmen. B. tesinskyi. 35–39: Spermatheca. 35. B. densatus. 36. B. dysommatiformis. 37. B. inconspicuus. 38. B. ruiterbos. 39. B. tesinskyi. 40–42: Female sternite VIII. 40. B. densatus. 41. B. inconspicuus. 42. B. tesinskyi. 43: Ovipositor. B. tesinskyi. Scale 0.50 mm for 25–28, 34, 40–43; 0.25 mm for 29–33, 35–39.