Epistomius, Borovec & Skuhrovec, 2017

Borovec, Roman & Skuhrovec, Jiří, 2017, Epistomius, a new genus of African forest litter Trachyphloeini, with descriptions of seven new species (Coleoptera: Curculionidae: Entiminae), Acta Entomologica Musei Nationalis Pragae (Acta. Ent. Mus. Natl. Pragae) 57 (2), pp. 645-676 : 649-654

Epistomius gen. nov.

( Figs 1A–C , 2A–I , 3A–G , 5A–G , 6A–G , 7A–G , 8A–G , 9A–G , 10A–G , 11A–G )

Type species. Epistomius colonnellii sp. nov., here designated.

Diagnosis. Small Trachyphloeini , less than 2.6 mm in body length, dorsum sparsely covered with appressed scales and glabrous ventrally; rostrum different in both sexes, not separated from head by any sulcus; frons glabrous; epistome short but wide, prominent anteriad and laterally creating sharp teeth directed dorsally; antennae and tibiae long and slender; metatibiae with apical surface glabrous, without corbels; claws connected at base; abdominal ventrites glabrous; tegmen without parameres; sternite VIII in females with triangular plate, short and robust apodeme terminating inside plate and reaching apex of plate, tip of plate with distinct Y-shaped process, prominent anteriad.

Description. Length 1.6–2.6 mm. Body dark brownish, antennae, extreme apical part of tibiae and tarsi paler, reddish brown, tarsi sometimes paler than antennae. Elytra sparsely covered with appressed irregularly shaped scales - subcircular, subsquared, subtriangular, or awned apicad, not covering integument, with moderately wide space between scales. Pronotum, and head with rostrum with dense subrounded scales, with fine fan-shaped striae, creating short, fine and dense fringes on almost half of circumference; scales leaving only short spaces between them. Gena and subgena densely squamose. Scape, femora and tibiae squamose; funicle and tarsi glabrous; club finely moderately densely setose with appressed and also short semiappressed setae. Scale-like setae on elytra long and conspicuous, distinctly longer on posterior declivity than on anterior disc, lance-shaped or subspatulate, creating one regular, moderately dense row on each interval. Setae on pronotum and head with rostrum slightly shorter than setae on elytral disc, on interocular space twice as long as the others. Scape, femora and tibiae with only very short and inconspicuous semiappressed setae, not prominent from outline. Colour pattern of body light brownish to greyish; raised setae paler. Head ( Fig. 1A ). Rostrum in four species more slender in males than in females ( Figs 5B–C , 6B–C , 9B–C , 10A–G ), in males 1.1–1.2× as wide as long, at base as wide as at apex to 1.1× wider at apex than at base, with distinctly and regularly concave sides, in place of anterior border of antennal scrobes abruptly, angle-shapedly tapered anteriad; in females 1.2–1.3× as wide as long, at base as wide as at apex to 1.1× wider at base than at apex, in basal half weakly tapered anteriad with faintly concave sides, in anterior half regularly rounded around antennal scrobes; in two species equal in both sexes, formed as females rostrum of previous species. Rostrum in lateral view ( Figs 5D , 6D , 7D , 8D , 9D , 10D , 11D ) weakly regularly convex, not separated from head. Epifrons widest at base, here equally wide as space between anterior margins of eyes, tapered anteriad with distinctly concave sides, flat, with slender longitudinal median stria along whole length. Epifrons when cleared of scales shiny, not separated from head by any stria or furrow, shallowly deepened, with longitudinal median stria and lateral longitudinal narrow keels, differently shaped in species. Frons glabrous and deepened, sometimes finely longitudinally striate, very short, creating narrow stripe along posterior border of epistome, without setae. Epistome distinctly developed, short but wide, asquamose, shiny, posteriorly distincly carinate and elevated, carina regularly arched, anteriorly declined to mandibles, bigger in males than in females, creating in lateral view sharp teeth directed dorsally, longer in males; in males epistome distinctly wider, in females equally wide as epifrons at midlength, in two species equal in males and females, similar to female epistome of previous species. Antennal scrobes ( Figs 5A , 6A , 7A , 8A , 9A , 10A , 11A ) in dorsal view clearly visible on anterior half of rostrum, open, pit-shaped; in lateral view short, reaching about half distance from antennal insertion to eyes, glabrous, weakly curved and moderately enlarged posteriad, with dorsal border directed to dorsal border and ventral border directed to ventral border of eyes. Head wide and convex; when cleared of scales shiny, sometimes with fovea and fine, narrow, longitudinal striae, mostly radiate. Eyes moderately large and convex, dorsally weakly prominent from outline of head; laterally subcircular, placed in dorsal third of head. Head including eyes in males 1.1–1.2× as wide and in females 1.2–1.3× as wide as rostrum at apex. Mandibles small, asquamose, trisetose. Submentum with pair of long, very fine setae. Gena densely squamose, subgena squamose in basal and lateral part, middle part glabrous.

Antennae ( Figs 5A , 6A , 7A , 8A , 9A , 10A , 11A ) long and slender. Scape long and slen- der, 4.9–6.1× as long as wide, 1.5–1.6× as long as funicle, faintly curved at midlength, weakly gradually enlarged in apical third, weakly slenderer than club or at most equally wide. Funicle 7-segmented, with segment I enlarged, long, slender and conical; segment II conical, distinctly shorter and narrower than segment I; segments III–VII at most 1.5× as wide as long; segments III–V weakly shorter than segments VI or VII. Segment I in club the longest one.

Pronotum ( Figs 5A , 6A , 7A , 8A , 9A , 10A , 11A ) in males weakly slenderer than in females, in males 1.4–1.5×, in females 1.4–1.6× as wide as long, regularly rounded, widest at midlength or just behind, more tapered anteriad than posteriad, regularly convex at disc without any furrow, stria or depressions. When cleared of scales shiny, sparsely irregularly and coarsely punctured, behind anterior margin bordered by transverse dense row of fine punctures. Pronotum laterally almost flat, behind anterior border lowered. Base straight. Anterior border in lateral view perpendicular to longitudinal axis, without ocular lobes or setae. Procoxal cavities contiguous, round, in middle of prosternum; procoxae subglobular. Scutellum not visible.

Elytra ( Figs 5A , 6A , 7A , 8A , 9A , 10A , 11A ) oval, widest at midlength with regularly rounded sides and broadly rounded at apex, in males 1.1–1.3×, in females 1.2–1.3× as long as wide, in lateral view strongly convex, posterior declivity overhanging apex. Base straight, slightly wider than base of pronotum, elytra in short distance behind base distinctly constricted; posthumeral calli weakly developed, visible in dorso-lateral view. Elytra 10-striate, striae slender, deeply sparsely punctured, intervals when cleared of scales shiny, almost flat, equally wide and elevated; interval 1 behind base somewhat tapered anteriad. Mesocoxae semiglobular, narrowly separate, mesosternal process about as wide as quarter of diameter of mesocoxa. Metacoxae shortly transverse.

Legs ( Figs 5A , 6A , 7A , 8A , 9A , 10A , 11A ). Femora unarmed, medially inflated, flattened. Tibiae long and slender; protibiae ( Figs 5E , 6E , 7E , 8E , 9E , 10E , 11A ) 5.5–6.4× as long as wide at midlength, at apex obliquely subtruncate, armed with 5–6 sparse, fine and slender yellowish, almost translucent spines and one conspicuous long and slender, almost straight spine directed inwards; lateral edge weakly curved inwards with short and shallow indentation just at apex; mesal edge distinctly enlarged inwards; meso- and metatibiae laterally fringed by dense fringe of fine, long, yellowish, bristle-shaped setae and one inward curved mucro, mucro longer in mesotibiae than in metatibiae and longer in females than in males. Apical surface of meso- and metatibiae glabrous, shiny; metatibiae without corbels. Tarsi long and slender, tarsomere I shorter than tarsomeres II and III together, tarsomere II transverse, tarsomere III distinctly wider than tarsomere II and bilobed, onychium long and slender, distinctly enlarged apicad. Claws fused in short basal part, then divergent.

Abdominal ventrites ( Fig. 1B ) in males equally wide and long to 1.04× wider than long, in females 1.06–1.13× as long as wide; ventrite 1 in middle slightly shorter than ventrites 2–4 together, behind metacoxa equally long as ventrite 2; ventrite 2 in middle slightly longer than ventrite 3 or 4; ventrite 5 in males shorter, subtrapezoidal, in females longer, subtriangular. Suture between ventrites 1 and 2 straight, fine and narrow, between 2–5 weakly arched, wide and deep. All ventrites asquamose, shiny, unpunctured, with several inconspicuous, short and fine, appressed piliform setae. Metaventral process obtuse, slightly wider than transverse diameter of metacoxa.

Sexual dimorphism. Males and females are easily distinguished by many external characters; males have rostrum more slender with distinctly wider and more conspicuous epistome ( Figs 5B , 6B , 7B , 8B , 9B , 10B , 11B ), rostrum at apex abruptly angularly tapered anteriad, while females have rostrum at apex regularly rounded around antennal scrobes ( Figs 5C , 6C , 7C , 8C , 9C , 10C , 11C ); pronotum slenderer in males; elytra slenderer in females; females have mucro in meso- and metatibiae longer than males; females have longer abdominal ventrites and longer, subtriangular ventrite segment 5.

Variability ( Figs 2A–I ). In three newly described species conspicuous variability in shape of raised elytral setae was registered. Similar variability in shape of setae is known only in Palaearctic Trachyphloeini , where parthenogenetic species with a large region of occurrence also show different shape of raised setae, because each new population is cloned without recombinations of genes. But this variability of amphigonic species in small regions is exceptional and for the time being known only from several other undescribed South African Trachyphloeini (R. Borovec, unpublished data). Although different shapes of setae suggest possibility of different species, these populations with different setae are conspecific in all other characters, as shape of rostrum, ratio of setal length in comparison between setae on the disc and posterior declivity, shape of antennal segments, tarsomeres, and penis. However, to conserve typical characters for all these three species, we include only one type of raised setae in the type series.

Male genitalia. Penis short, well sclerotised, temones 3.1–4.7× longer than body of penis and 1.7–3.1× longer than tegminal manubrium; endophallus with thick flagellate sclerite ( Figs 5G , 6G , 7G , 8G , 9G , 10G , 11G ). Tegmen with moderately wide ring without parameres, its manubrium 1.3–2.3× as long as ring diameter. Sternite IX with spiculum gastrale anteriorly enlarged to flat, slender elongate plate, posteriorly with fused basal arms and with two very slender, regularly curved hemisternites. Shape of penis differing among the species ( Figs 3A–G ).

Female genitalia. Gonocoxites short and wide, evenly tapered apicad, with long and slender apical styli with tuft of 3–4 fine setae ( Fig. 1C ). Sternite VIII ( Fig. 1C ) with short and robust apodeme, 2.0–2.5× as long as plate, evenly enlarged to plate, terminating just inside plate and here also robust, reaching apical part of plate; plate subtriangular, with basal and apical margin slender but developed, tip of plate distinctly more sclerotised then remaining part of plate, Y-shaped, enlarged, prominent anteriad. Spermatheca ( Figs 5F , 6F , 7F , 8F , 9F , 10F , 11F ) large, crescentic, with short and robust cornu and elongated corpus, irregularly tapered anteriad and posteriad, without differentiated nodulus and ramus. Gonocoxites, sternum VIII and also spermatheca not differing among the species.

Etymology. The Latin name of this new genus reflects the conspicuous large epistome. Gender is masculine.

Biology. All type material was collected either by sifting or in unbaited pitfall traps, all in afromontane indigenous forest or rain forest. All species are amphigonic.

Distribution. Known only from South Africa, provinces Eastern Cape, KwaZulu-Natal, and Mpumalanga ( Fig. 4 ).

Species included. Seven newly described species below.

Taxonomical remarks. Epistomius gen. nov. belongs to the tribe Trachyphloeini based on the following morphological characters: rostrum wider than its length; scrobes placed subdorsally, laterally directed towards the eyes and evanescent before them; epifrons with well defined margins along the whole length, at base as wide as the space between anterior eye margins; elytra without developed humeral calli, grown together; the entire dorsal part of body densely squamose; and metatibiae lacking corbels. The last character is in fact the only character allowing the separation of both tribes, Trachyphloeini and Embrithini , which include not only large arboricolous and floricolous genera and species, but also many small terricolous forms, for example Afrophloeus Borovec & Oberprieler, 2013 , and also some still undescribed genera with undescribed species (Borovec, unpublished data).

The group of South African Trachyphloeini includes up to now only two described genera - Pentatrachyphloeus Voss, 1974 and Nama Borovec & Meregalli, 2013 . The genus Epistomius gen. nov. is easily distinguishable from Pentatrachyphloeus species by the following characters: rostrum continuous with the head, without any transverse sulcus (vs. with slen- der transverse sulcus); protibiae slender and long, 5.5–6.4× as long as wide, with fringe of yellowish setae only at apex (vs. short and robust, 3.6–4.9× as long as wide, armed with 4–6 small, short and fine, sparse spines); frons glabrous (vs. squamose); ventrites glabrous (vs. densely squamose); epistome prominent anteriad and laterally creating sharp teeth directed dorsally (vs. small, dorsally hardly visible); elytra without posthumeral calli (vs. with posthumeral calli); and tip of plate in female sternite VIII with distinct Y-shaped process, prominent anteriad (vs. plate umbrella-shaped, apically broadly rounded). The genus Epistomius gen. nov. is also very easily distinguishable from the genus Nama mainly thanks to claws connected at base ( Nama species has free claws).

The status of the new genus and its comparison with the known Palaearctic Trachyphloeini genera is as follows: Epistomius gen. nov. differs from both Trachyphloeus and Pentatrachyphloeus in the identical set of characters, except that Trachyphloeus lacks the sulcus between head and rostrum, and posthumeral calli. The new genus, Epistomius gen. nov., may probably be close to genera Pelletierellus Borovec, 2009 , Zarazagaia Borovec, 2009 , and Stuebenius Borovec, 2009 , due to the identical status of the following morphological characters: absent ocular lobes, striae in lateral part of head, laterally triangular scrobes, and claws connected at base. The new genus is well distinguishable from the first two mentioned genera also by rostrum not separated by shallow transverse furrow, pronotum without depressions and furrows, ventrites glabrous, tegmen lacking parameres, sternite VIII in females with apical Y-shaped process, and smaller body size; and from Pelletierellus also due to scrobes not visible dorsally. Epistomius gen. nov. is easily distinguishable from the genus Stuebenius by rostrum not separated by shallow transverse furrow, slender and moderately long scape and tibiae, ventrite 2 distinctly shorter than ventrites 3 and 4 together, suture between ventrite 1 and 2 straight, sternite VIII in females with short and robust apodeme, and with apical Y-shaped process.

Figures

Fig. 1. Epistomius colonnellii sp. nov.A – rostrum without scales, dorsal view, B – abdominal ventrites; C – female sternite 8 and gonocoxites, dorsal view.

Fig. 2. Variability in elytral scales in three species.Epistomius colonnellii sp. nov.(A – lateral view, B, C – variability in dorsal view); Epistomius natalensis sp. nov. (D – lateral view, E, F – variability in dorsal view); Epistomius niger sp. nov. (G – lateral view, H, I – variability in dorsal view).

Fig. 3. Apex of penis.A – Epistomius bulirschi sp. nov.; B – Epistomius colonnellii sp. nov.; C – Epistomius janaki sp. nov.; D – Epistomius natalensis sp. nov.; E – Epistomius ngomiensis sp. nov.; F – Epistomius niger sp. nov.; G – Epistomius wanati sp. nov.

Fig. 5. Epistomius bulirschi sp. nov. A – habitus, dorsal view, holotype, male; B – rostrum, male, dorsal view; C – rostrum, female, dorsal view; D – rostrum, male, lateral view; E – protibia, male; F – spermatheca; G – aedeagus. Scale bars: 1 mm (A), 0.5 mm (G) and 0.2 mm (F).

Fig. 6. Epistomius colonnellii sp. nov. A – habitus, dorsal view, holotype, male; B – rostrum, male, dorsal view; C – rostrum, female, dorsal view; D – rostrum, male, lateral view; E – protibia, male; F – spermatheca; G – aedeagus. Scale bars: 1 mm (A), 0.5 mm (G) and 0.2 mm (F).

Fig. 7. Epistomius janaki sp. nov. A – habitus, dorsal view, holotype, male; B – rostrum, male, dorsal view; C – rostrum, female, dorsal view; D – rostrum, male, lateral view; E – protibia, male; F – spermatheca; G – aedeagus. Scale bars: 1 mm (A), 0.5 mm (G) and 0.2 mm (F).

Fig. 8. Epistomius natalensis sp. nov. A – habitus, dorsal view, holotype, male; B – rostrum, male, dorsal view; C – rostrum, female, dorsal view; D – rostrum, male, lateral view; E – protibia, male; F – spermatheca; G – aedeagus. Scale bars: 1 mm (A), 0.5 mm (G) and 0.2 mm (F).

Fig. 9. Epistomius ngomiensis sp. nov. A – habitus, dorsal view, holotype, male; B – rostrum, male, dorsal view; C – rostrum, female, dorsal view; D – rostrum, male, lateral view; E – protibia, male; F – spermatheca; G – aedeagus. Scale bars: 1 mm (A), 0.5 mm (G) and 0.2 mm (F).

Fig. 10. Epistomius niger sp. nov. A – habitus, dorsal view, holotype, male; B – rostrum, male, dorsal view; C – rostrum, female, dorsal view; D – rostrum, male, lateral view; E – protibia, male; F – spermatheca; G – aedeagus. Scale bars: 1 mm (A), 0.5 mm (G) and 0.2 mm (F).

Fig. 11. Epistomius wanati sp. nov. A – habitus, dorsal view, holotype, male; B – rostrum, male, dorsal view; C – rostrum, female, dorsal view; D – rostrum, male, lateral view; E – protibia, male; F – spermatheca; G – aedeagus. Scale bars: 1 mm (A), 0.5 mm (G) and 0.2 mm (F).

Fig. 4. Distribution of Epistomius species in South Africa; Epistomius bulirschi sp. nov. (yellow circle); Epistomius colonnellii sp. nov. (brown circles); Epistomius janaki sp. nov. (violet circles); Epistomius natalensis sp. nov. (blue circles); Epistomius ngomiensis sp. nov. (red circles); Epistomius niger sp. nov. (green circles); and Epistomius wanati sp. nov. (orange circle).