Andringitrabius Hustache, 1956

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 : 102-104

Andringitrabius Hustache, 1956

Figs (1, 13, 14)

Andringitrabius Hustache, 1956: 73 (original description); Alonso-Zarazaga & Lyal 1999: 187 (catalogue).

Type species. Andringitrabius polymitus Hustache, 1956 by original designation. Gender masculine.

Diagnosis. Small Oosomini 3.2 mm long; rostrum in dorsal view wider than long, at base slightly wider than at apex; epifrons at base distinctly narrower than space between anterior margins of eyes, posteriorly separated from head by wide transverse furrow with ill-defined margins; frons glabrous; antennal sockets dorsally placed, pit-shaped, in lateral view slightly enlarged posteriad, directed towards eye but not reaching it; antennal scape reaching anterior margin of pronotum when folded, at apex narrower than club; antennae and legs glabrous; apex of elytra not hidden by overhanging slope; metatibiae with apical surface glabrous and with setose bevel; claws free, divaricate.

Description. Body length 3.20 mm. Ground colour of body ( Fig. 1 ) black, antennae and legs reddish brown. Vestiture of body consisting of dense appressed rounded scales completely hidden integument, leaving only narrow elytral rows and median longitudinal stripe on pronotum glabrous; the entire antennae and legs glabrous with very sparse appressed short piliform setae and short, sparse, semi-erect piliform setae. Elytra with one regular row of short, semi-erect piliform setae; pronotum and rostrum with head with irregularly scattered identical setae, distinctly shorter than elytral ones, visible only in lateral view. Colour pattern of body vestiture green with weak metallic sheen on elytra and head with rostrum, grey on pronotum.

Rostrum ( Figs 13, 14 ) short, 1.2× as wide as long, in dorsal view widest at base, evenly tapering apicad, with concave sides; in lateral view slightly regularly vaulted. Epifrons narrow, at base 0.5× as wide as rostrum in respective part, with slightly concave sides, at base distinctly narrower than space between anterior margins of eyes, dorsally with longitudinal furrow, posteriorly separated from head by shallow transverse furrow with ill-defined margins. Frons moderately large, glabrous, posteriorly not carinated, with 4 pairs of fine apical setae. Epistome not developed. Antennal sockets in dorsal view well visible in anterior third of rostrum, pit-shaped; in lateral view short, placed near dorsal margin of rostrum, slightly enlarging posteriad and curved, with dorsal margin directed towards dorsal margin of eye and ventral margin towards middle of eye, separated from eye by wide squamose stripe. Vertex almost flat, wide. Head wide, behind eyes short and distinctly enlarged posteriad. Eyes moderately small, weakly convex, hardly prominent from outline of head in dorsal view, in lateral view placed nearer dorsal margin of head, subcircular. Mandibles with three fine setae, asquamose.

Antennae ( Fig. 1 ) with scape somewhat slender, 6.4× as long as at apex wide, 1.2× as long as funicle, reaching anterior margin of pronotum when folded, slightly regularly curved at middle, slightly evenly enlarging apicad in apical half, at apex slightly narrower than club. Funicle with 7 articles; articles 1 and 2 slender, long, conical, articles 3–7 not distinctly wider than long. Clubs spindle-shaped.

Pronotum ( Fig. 1 ) 1.3× as wide as long, widest at midlength, with sides rounded, tapering more anteriad than posteriad, behind anterior margin weakly constricted. Disc regularly domed, base slightly arched. Pronotum in lateral view almost flat. Anterior margin in lateral view without setae or ocular lobes. Procoxal cavities contiguous, round, located at middle of prosternum. Scutellar shield dorsally invisible.

Elytra ( Fig. 1 ) oval, 1.4× as long as wide, widest slightly before midlength, with sides weakly rounded, apically narrowly rounded, humeral and subhumeral calli missing; apex of elytra visible in dorsal view, not hidden by overhanging slope. Elytra 10-striate, striae punctate; interstriae flat. Elytral profile in lateral view slightly vaulted.

Femora medially somewhat swollen, unarmed. Tibiae moderately slender, straight; protibiae almost 8× as long as at midlength wide, with lateral side straight, apically rounded, with fringe of fine, sparse and short setae, inner portion with brownish mucro; meso- and metatibiae with short mucro; apical surface of meso- and metatibiae glabrous, outside fringed by fine setae, inside armed with short sparse spines, brownish; metatibiae 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 longer than tarsomere 3; claws free, weakly divaricate.

Abdominal ventrites and terminalia not examined.

Biology. Unknown.

Distribution. The genus is native to Madagascar.

Species included. The genus was described as monotypic.

Taxonomic remarks. Hustache (1956) did not assign his new genus to any tribe, and also did not mention any similar genera with which he made comparisons. He only briefly defined the genus as distinguishable by scrobes fully dorsally placed, completely visible in dorsal view and by free claws. Thus, the genus with this incomplete description was listed as Entiminae incertae sedis in the catalogue of Alonso-Zarazaga & Lyal (1999).

Andringitrabius belongs to the tribe Oosomini based on its free claws, dorsally placed antennal sockets, trisetose mandibles, 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. The precise position of Andringitrabius within Oosomini is not clear. Because it is not possible to borrow type specimens from the Paris museum, I was not able to examine the ventral part of the type specimen or to dissect it, and thus examine the terminalia. In only dorsally visible morphological characters Andringitrabius is similar to the genus Bulirschius described below, as both genera share the rostrum separated from the head by a shallow transverse furrow with ill-defined margins, epifrons at base narrower than distance between the inner margins of the eyes and antennal scapes at apex narrower than clubs. It is possible to distinguish Andringitrabius by the elytra in lateral view gradually tapered apicad, with their apices clearly visible in dorsal view, not obscured by the overhanging slope of the elytral declivity, epifrons mostly glabrous, sparsely covered with appressed scales, antennal scapes and tibiae glabrous and the rostrum in lateral view longer, with the ventral margin not shorter than thickness of the rostrum at its base. When other Madagascan material is available for study, it would be desirable to examine other characters not visible in dorsal and lateral view, including internal characters, to prepare a more precise definition of the genus.

Figures

FIGURES 1–4. Dorsal habitus. 1. Andringitrabius polymitus. 2. Holotype labels of Andringitrabius. 3. Bulirschius densatus. 4. B. dysommatiformis. 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.