Tribasodites dilophus, Yin, 2022

Yin, Zi-Wei, 2022, The Batrisini of Tibet: unveiling an enigmatic ant-loving beetle diversity at Earth’s “ Third Pole ” (Coleoptera, Staphylinidae, Pselaphinae), Zootaxa 5111 (1), pp. 1-211 : 152-154

Tribasodites dilophus sp. nov.

( Figs 65 , 86A , 96B, C )

Chinese common name: ḦẆûḃà甲

Type material (20 exx.). HOLOTYPE: CHINA: ♂ , ‘ China: Xizang, Nyingchi City, pass nr. Chongzhe , 29°34’31”N, 94°23’01”E, 3230 m, 03.vii.2018, mixed leaf litter, sifted, Cheng, Peng & Shen leg. [ƱẪffżΦĖṉữ]’ ( SNUC) . PARATYPES: CHINA: 2 ♂♂, same data as that of holotype; 5 ♂♂, 12 ♀♀, also from Nyingchi, except ‘ Kading Valley , 29°45’32”N, 94°10’09”E, 3200 m, 08.vii.2021, Peng, Yin & Zhang leg., Ʊ Ẫffż 市巴Ù区ϮŤ沟 Ḩā 区 ’ ( SNUC) .

Diagnosis. Male. Body length approximately 2.1 mm. Head sub-rounded at base, approximately as wide as pronotum, tempus moderately long, with rounded posterolateral margin, vertex lacking sulcus, with relatively large, sparsely setose foveae, with distinct mediobasal carina extending from head base anteriorly slightly beyond level of anterior margin of vertexal foveae, with distinct lateral carina from base to posterior margin of antennal tubercle; antenna elongate, lacking modifications, antennomeres elongate. Pronotum with laterally carinate median and shallow lateral longitudinal sulci, with pair of longitudinal discal carinae composed of spines, with pair of large antebasal and small marginal spines. Discal stria of elytron extending posteriorly to approximately basal 1/3 of elytral length; disc finely punctate. Mesotrochanter with distinct ventral spine; metatrochanter with strongly curved projection on ventral margin. Aedeagus slightly asymmetric; median lobe with large basal capsule and elongate foramen, ventral stalk broad apically, lacking distinct dorsal lobe or parameres. Female. Body length approximately 2.0 mm, antenna shorter than male, legs lacking modifications, genitalia as in Fig. 65I .

Description. Male. Body ( Fig. 65A ) length 2.08–2.15 mm; color reddish-brown, tarsi and mouthparts lighter. Dorsal surface of body covered with relatively dense pubescence.

Head ( Fig. 65B ) sub-rounded at base, approximately as wide as long, length 0.44–0.46 mm, width across eyes 0.46 mm; vertex smooth, lacking sulcus, vertexal foveae (dorsal tentorial pits) setose, relatively large, mediobasal carina distinct, extending from head base anteriorly to slightly beyond level of anterior margin of vertexal foveae, lateral carina distinct, extending from base to posterior margin of antennal tubercle; posterolateral margin rounded; frons anteriorly demarcated from clypeus by thin frontal-clypeal ridge, area between moderately raised antennal tubercles weakly impressed; clypeus with smooth surface, its entire anterior margin strongly carinate and moderately raised; ocular-mandibular carina complete. Venter with smooth surface; small gular foveae (posterior tentorial pits) originating from shared oval opening, with thin median carina extending from opening anteriorly to mouthparts. Compound eyes prominent, composed of approximately 45–50 ommatidia. Antenna elongate, length 1.08–1.16 mm, indistinct club formed by enlarged apical three antennomeres; antennomere 1 thick, subcylindrical, 2–8 each slightly elongate, 8 shortest, 9 much wider and longer than 8, elongate, 10 shorter than 9, subconical, 11 largest, slightly longer than 9 and 10 combined, sub-fusiform.

Pronotum ( Fig. 65B ) approximately as long as wide, length 0.46–0.48 mm, width 0.44–0.45 mm, widest at middle; lateral margins rounded at middle, convergent apically and parallel at basal 1/4; disc slightly convex, finely punctate, thin median longitudinal sulcus with slightly carinate margins, posteriorly confluent with oval antebasal impression and short mediobasal carina, pair of discal longitudinal carinae ( Fig. 65C ) each composed of five distinct spines, with shallow lateral longitudinal sulci; with pairs of large antebasal and small marginal spines; lateral antebasal foveae small and setose; with small outer and inner pair of basolateral foveae. Prosternum with anterior part slightly longer than coxal part, with small lateral procoxal foveae; distinct hypomeral ridge extending from base to middle of anterior part, with punctiform lateral antebasal hypomeral pit; margin of coxal cavity slightly carinate.

Elytra much wider than long, length 0.66–0.69 mm, width 0.76–0.77 mm; each elytron with three moderately large, asetose basal foveae; discal stria short, extending posteriorly from outer basal fovea to approximately basal 1/3 elytral length; humerus denticulate, subhumeral fovea present, carinate marginal stria extending from fovea to posterior margin of elytron.

Mesoventrite short, demarcated from metaventrite by transverse carinae; median mesoventral foveae narrowly separated, originating from shared transverse opening, large lateral mesoventral foveae forked internally, with short mesoventral process, with complete marginal stria. Metaventrite prominent admesally, inclined towards middle, with well-developed lateral mesocoxal foveae, with two lateral metaventral foveae, posterior margin roundly emarginate and with narrow split at middle.

Legs elongate; procoxa with exceptionally long seta at base; mesotrochanter ( Fig. 65D ) with distinct ventral spine, mesotibia with small apical spur; metatrochanter ( Fig. 65E ) with long, strongly curved ventral projection, metatibia with short pencil-like apical tuft of setae.

Abdomen widest at lateral margins of tergite 1 (IV), length 0.54–0.61 mm, width 0.65–0.67 mm. Tergite 1 (IV) approximately twice as long as 2 (V), lacking basal sulcus, with mediobasal and two pairs of basolateral foveae, with pair of moderately long, thick discal carinae, marginal carinae complete, oblique inner carina thinner than outer one; tergite 2 (V) slightly longer than 3 (VI), with one pair of small mediobasal foveae, two pairs of small basolateral foveae and thin marginal carinae, 3 (VI) with small basolateral foveae and thin marginal carinae, 4 (VII) shorter than tergites 2 and 3 combined, with one pair of small basolateral foveae, lacking marginal carinae; tergite 5 (VIII) semicircular, transverse, posterior margin roundly emarginate at middle. Sternite 2 (IV) with one pair of mediobasal and three pairs of basolateral foveae, lacking lateral carina; midlength of sternites 2–4 (IV–VI) gradually shorter, 5 (VII) slightly longer than 4, sternites 3–4 each with three pairs and 5 with one pair of small basolateral foveae, sternite 6 (VIII) transverse, posterior margin broadly emarginate, roundly convex at middle, sternite 7 (IX) ( Fig. 65F ) membranous, with weakly sclerotized central part.

Aedeagus ( Fig. 65G, H ) 0.31 mm long, in dorsal view moderately asymmetric, elongate; median lobe with large laterally broad basal capsule and elongate foramen, ventral stalk in dorsal view broad, largely membranous, with weakly sclerotized, curved and apically expanded ventral lobe; lacking distinct articulated dorsal lobe or parameres.

Female. Similar to male in external morphology; antenna as long as male; legs lacking modifications; each compound eye composed of approximately 35 ommatidia. Measurements (as for male): body length 2.0– 2.07 mm; length/width of head 0.43/ 0.43–0.45 mm, pronotum 0.45/ 0.44 mm, elytra 0.62–0.65/ 0.72–0.74 mm; abdomen 0.57– 0.58/ 0.64–0.65 mm; length of antenna 1.07–1.14 mm; genitalia weakly sclerotized ( Fig. 65I ), with elongate, forked lateral arms, maximum width 0.20 mm.

Comparative notes. Tribasodites dilophus belongs to a group of species that share elongate and simple male antennae, relatively long postocular margins, often with longitudinal rows of discal spines on the pronotum, and the aedeagus usually with elongate median and dorsal lobes. This species differs by the broad ventral stalk and dorsal lobe of the aedeagus, and by its distribution.

Distribution. Chagyib District (Nyingchi), Xizang, SW China ( Figs 86A , 96B, C ).

Etymology. The specific epithet is taken from the Greek ‘ dilophos ’ (two-crested), referring to the two longitudinal rows of spines on the pronotal disc.

Figures

FIGURE 65. Morphology of Tribasodites dilophus sp. nov. (A–H. Male. I. Female). A. Dorsal habitus. B. Head and pronotum. C. Pronotum, in dorsolateral view. D. Mesotrochanter. E. Metatrochanter. F. Sternite 7 (IX). G, H. Aedeagus, lateral (G) and ventral (H). I. Genitalia. Scale bars: 0.5 mm in A; 0.3 mm in B; 0.2 mm in C, G, H; 0.1 mm in D–F, I.

FIGURE 86. Distribution of Tibetan Batrisini. A. Tribasodites dilophus sp. nov. (circle), T. elongatus sp. nov. (triangle) and T. grandiceps sp. nov. (square). B. T. gyirong sp. nov. (circle), T. kiypu sp. nov. (triangle) and T. mirabilis sp. nov. (square). C. T. prolixicornis sp. nov. (circle), T. Tribasodites pugiunculus sp. nov. (triangle) T. vertexalis sp. nov. (square) and T. yatung sp. nov. (diamond).

FIGURE 96. Environment of and collecting sites at Nyingchi area (ffż地区). A. Gongbo'gyamda (工布ȕḭ). B. Zhongzhe Village (ΦĖ村). C. Kading Valley (ϮŤ沟). D. Chongge Cuo (ṗẋś). E, F. A slope near Serjila mountain pass (DzĻŃ山 口). Photo Credit: A, B, E, F by Zhong Peng.