Oberprielerius Hlaváč & Borovec, 2022

Hlaváč, Peter & Borovec, Roman, 2022, Oberprielerius, a new genus for Anchonidium uniformeVoss, 1974, a microphthalmic species of Rhythirrinini (Coleoptera: Curculionidae: Cyclominae) from South Africa, Zootaxa 5196 (1), pp. 128-134 : 129-132

Oberprielerius Hlaváč & Borovec gen. n.

( Figs 1–9 )

Type species, by present designation: Anchonidium uniforme Voss, 1974 . Gender masculine.

Diagnosis. Small Rhythirrinini , less than 3 mm long; rostrum subcylindrical, almost twice as long as wide at its base; epifrons evenly tapering to antennal insertions; frons glabrous; epistome indistinct; ventral side glabrous; antennal sockets in profile directed towards lower margin of eyes; eyes small, reduced, composed of 6–7 ommatidia; mouthparts phanerognathous; antennae slender, funicles 7-segmented; prothorax slightly longer than wide, lacking ocular lobes; elytra distinctly elongate; protibiae slender, slightly bent inwards apically, not expanded laterally; suture between ventrites 1 and 2 fine, sinuose; venter glabrous; distal gonocoxites elongate, lacking styli, with apical third sparsely setose, setae moderately long and stiff; sternite VIII of female with apodeme terminating inside of long oval plate, there forked.

Description. Body length 1.9–2.6 mm. Body ( Fig. 1 ) integument pale to dark brownish, whole antennae or only funicles with clubs and tibiae and tarsi paler, reddish or yellowish brown. Dorsal part of body, scapes and legs except tarsi covered by appressed scales, scales not fully covering integument, leaving narrow glabrous spaces between scales on pronotum; striae on elytra distinct; venter of body ( Fig. 2 ) glabrous, only subgenae densely squamose and meso- and metaventrite sparsely squamose. Elytra with inconspicuous regular row of erect setae on each interstria, pronotum, head and rostrum with similar, densely irregularly scattered setae. Venter ( Figs 2–3 ) with very short and sparse, inconspicuous, piliform appressed setae.

Rostrum narrow, subcylindrical, slightly less than twice as long as wide at base, evenly tapering apicad in basal third and then widening apicad again, rounded around antennal sockets; in profile with slightly arcuate dorsal margin and straight ventral margin; epifrons dorsally flat, widest at base, tapering apicad with slightly rounded sides in majority of its length, with short and shallow concavity only just before antennal insertions, posteriorly separated from head by shallow transverse sulcus. Frons glabrous, smooth, conspicuous, slightly declined, posteriorly not carinate, with 6–7 pairs of fine erect setae, unevenly scattered. Epistome indistinct. Mandibles small, asquamose, without mandibular scars, bisetose. Antennae inserted in about apical quarter; antennal sockets in dorsal view narrowly reniform with visible continuation to scrobes; scrobes narrow, only slightly enlarging posteriad, almost straight, not sharply set off from densely squamose rostrum all around, directed towards lower margin of eye, not continuing onto venter of rostrum.Head short and broad, distinctly enlarged posteriad.Eyes small, reduced, composed of 6–7 ommatidia, in dorsal view hardly visible, flat, not prominent from outline of head; in lateral view placed in middle of head, much smaller than height of head above or below eyes, diameter about half width of antennal clubs. Mouthparts ( Fig. 3 ) phanerognathous, leaving maxillae exposed continuously at sides of prementum.

Antennae slender, scapes in repose reaching posterior border of eyes, funicles 7-segmented, segment 1 longest, 3–7 shorter and subequal, 7 not closely approximated to club.

Prothorax elongate, slightly longer than wide, slightly narrower than elytra, anterior margin laterally straight, not forming ocular lobes, lacking vibrissae, directed distinctly obliquely ventrad to procoxae. Procoxal cavities circular, confluent; procoxae subglobular, placed much closer to posterior margin of prothorax; anterior margin ventrally arched. Scutellar shield indistinct.

Elytra distinctly elongate, slender, somewhat convex, 10–striate; strial punctures large, not hidden under vestiture or encrustation; interstriae flat. Apices of elytra visible in dorsal view. Wingless. Mesocoxal cavities circular, separated by about one third their width. Metacoxae slightly transverse, laterally not reaching elytral margins, separated by 1.25 their width.

Legs moderately slender. Femora of all legs unarmed, slightly inflated in distal third; tibiae straight, not denticulate, distinctly mucronate, lacking spurs and unci, apices not expanded laterally or mesally, protibiae slightly bent inwards apically, meso- and metatibiae straight; tarsi slender, with segment 1 slightly longer than wide and shorter than 2 + 3 together; 2 slightly transverse; 3 deeply lobed and onychium longer than 2 + 3 together; claws free, moderately long, distinctly divergent.

Abdominal ventrites slender; ventrite 1 in middle 1.3 × longer than 2; 2 about as long as 3 + 4 combined, these subequal in length; 5 in males shorter than 3 + 4 combined, in females as long. Suture between ventrites 1 and 2 fine, sinuose, the others straight, wide and coarse. Metaventral process obtuse.

Male terminalia ( Figs 4–6 ). Penis ( Figs 4, 5 ) short, temones twice as long as body of penis; endophallus with two short, parallel sclerites. Tegmen with narrow complete ring, lacking parameres, manubrium distinctly longer than diameter of ring. Sternite IX ( Fig. 6 ) anteriorly slightly curved with small oval plate, posteriorly with basally fused arms.

Female terminalia ( Figs 7–9 ). Ovipositor ( Fig. 7 ) long and slender; distal gonocoxites cylindrical, elongate, evenly tapering apicad, lacking styli, apical third sparsely setose, setae moderately long and fine, denser at apex. Sternite VIII ( Fig. 8 ) with medium-sized apodeme, terminating inside of plate, there forked; plate long oval, weakly sclerotised, more laterally sclerotisation stronger, anterior margin membranous, fringed by short and fine setae. Spermatheca ( Fig. 9 ) C-shaped, with distinct ramus and collum.

Sexual dimorphism. Ventrite 5 in males short, apically subtruncate; in females longer, apically rounded.

Derivation of name. We cordially dedicate this new genus to our colleague and friend, Rolf G. Oberprieler (CSIRO National Collection of Insects, Canberra, Australia), specialist on weevils, author of the last Cyclominae studies and also an expert on the South African weevil fauna.

Distribution. Republic of South Africa (Western Cape, Table Mountain).

Taxonomic placement. The single species included in Oberprielerius thus far, O. uniformis , lacks the typical character of the subfamily Molytinae , i.e., the long tibial uncus, and must therefore be removed from this subfamily. Among other characters, its phanerognathous mouthparts and the absence of mandibular scars excludes it also from the subfamily Entiminae Schoenherr, 1823 , which also includes edaphic microphthalmic forms. Its combination of characters, namely the elongate, slightly curved rostrum, bisetose mandibles, indistinct epistome, 7-segmented funicles with elongate segment 1, long scrobes directed towards ventral margin of flat eyes, mucronate tibiae and distal gonocoxites of ovipositor produced into prongs, lacking styli but with long apical setae, correspond to the cyclomine tribe Rhythirrinini Lacordaire, 1863 , as delineated by Oberprieler (2010) and later characterised in more detail by the same author (Oberprieler 2014). Oberprielerius differs from this definition only by lacking tubercules on the pronotum and elytra (but Rhyparosomus Schoenherr, 1842 also has no such tubercles) and by lacking ocular lobes.

Oberprielerius shares no obvious characters with any currently known genus of Rhythirrinini . Its small body size, with reduced eyes and lacking small protrusions, corresponds to a way of life in dense plant litter or even in the soil, which is typical of other Rhythirrinini living in such habitats in the fynbos and karoo biomes of South Africa, as observed by the second author by way of numerous specimens of Rhyparosomus and also Terapopus Schoenherr, 1845 collected in such habitats. Oberprielerius can be thus easily distinguished from other genera of Rhythirrinini by the following set of unique characters: epifrons tapering anteriad, at apical portion with dorsolateral carinae closer together than the lateral outlines of the rostrum in its respective part, eyes small, reduced to 6–7 ommatidia, prothorax lacking ocular lobes, ventral side of body glabrous, distal gonocoxites sparsely scattered with long fine setae in addition to apical tuft.

Remarks. Microphthalmy in weevils was recently defined by Escalona & Oberprieler (2021) as the reduction in the number of ommatidia so that there are only four or fewer ommatidia across the length of the eyes. The eyes of Oberprielerius uniformis are only three ommatidia long, counted in a row from the anterior to the posterior margin, and the species can thus also be regarded as being microphthalmic. According to our present knowledge, it is the first microphthalmic species of Rhythirrinini .

Figures

FIGURES 1–3. Habitus and head of Oberprielerius uniformis. 1. Dorsal habitus. 2. Ventral habitus. 3. Head, ventral view.

FIGURES 4–9. Genital structures of Oberprielerius uniformis. 4. Aedeagus, lateral view. 5. Aedeagus, dorsal view. 6. Sternite IX (spiculum gastrale) of male. 7. Ovipositor, ventral view. 8. Sternite VIII of female, ventral view. 9. Spermatheca.