Batrisiella acclivis, 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 : 72-74

Batrisiella acclivis sp. nov.

( Figs 30 , 80B , 95A, B )

Chinese common name: ṖḎ小毛唇à甲

Type material (9 exx.). HOLOTYPE: CHINA: ♂ , ‘ China: Xizang, Cona County, Lebu Valley , pass to Mama Vill., 27°50’16”N, 91°45’48”E, 2400–2700 m, 04.vii.2021, Z. Peng, Z. Yin & W. Zhang leg., ƱẪDZḄ县勒布沟Þ玛 乡 ’ ( SNUC) . PARATYPES: CHINA: 6 ♂♂, 2 ♀♀, same data as that of holotype (all paratypes in SNUC) .

Diagnosis. Male. Body length approximately 1.8 mm. Head sub-rectangular at base; vertexal foveae moderately large and asetose, surrounding areas strongly impressed, lacking sulcus connecting foveae; antenna moderately elongate; antennomeres each slightly elongate, 9–11 enlarged to form moderately distinct club. Discal stria of elytron extending to approximately apical 1/5 of elytral length. Legs with profemur strongly swollen distally, with dense trichomes at apex, mesotibia with tiny tubercle at apex. Aedeagus strongly asymmetric; median lobe with large basal capsule, basoventral projection short, ventral stalk broad in lateral view; dorsal lobe strongly curved, apically split into two elongate sclerites; parameres reduced to single, small membranous structure. Female. Body length approximately 1.80 mm; antenna shorter, legs lacking modifications, genitalia as in Fig. 30I .

Description. Male. Body ( Fig. 30A ) length 1.80–1.85 mm; color reddish-brown, tarsi and mouthparts lighter. Dorsal surface of body covered with short pubescence.

Head ( Fig. 30B ) sub-rectangular at base, approximately as long as broad, length 0.38–0.39 mm, width across eyes 0.40–0.42 mm; vertex finely punctate, with moderately large, asetose vertexal foveae (dorsal tentorial pits), lacking U-shaped sulcus connecting foveae, surrounding areas of foveae strongly impressed, median carina thin and long, with broad transverse sulcus between weakly raised antennal tubercles; frons broadly impressed medially, smooth, anteriorly confluent with clypeus; clypeus coarsely punctate, anterior margin carinate and moderately raised; ocular-mandibular ridge (with upper and lower carinae) broad. Venter with two tiny gular foveae (posterior tentorial pits) originating from shared impression, with thin median carina extending from foveae anteriorly to mouthparts. Compound eyes prominent, composed of approximately 35 ommatidia. Antenna moderately elongate, length 0.91–0.92 mm, apical three antennomeres forming moderately distinct club; antennomere 1 thick, subcylindrical, laterally with internal glandular structure ( Fig. 30C ), 2–8 each elongate, 8 smallest, 9 much larger than 8, 10 as long as and broader than 9, 11 largest, as long as 9 and 10 combined, sub-conical.

Pronotum ( Fig. 30B ) approximately as long as broad, length 0.43–0.44 mm, width 0.42–0.43 mm, widest at middle; lateral margins rounded; disc slightly convex, finely punctate, pubescent, median longitudinal sulcus broad, slightly shorter than semicircular lateral sulci in dorsal view, the latter extending from dorsal surface laterally and posteriorly and then fusing with lateral ends of antebasal sulcus; lacking median antebasal fovea, lateral antebasal foveae connected by transverse antebasal sulcus; outer and inner pair of basolateral foveae distinct. Prosternum with anterior part slightly longer than coxal part, with distinct lateral procoxal foveae; hypomeral ridge extending from base to middle of anterior part, with round lateral antebasal hypomeral pit; margin of coxal cavity weakly carinate.

Elytra much wider than long, length 0.58–0.60 mm, width 0.71–0.76 mm; each elytron with two large, asetose basal foveae, lacking subbasal fovea; discal stria extending from outer basal fovea to approximately apical 1/5 of elytral length; humerus angulate, small subhumeral fovea present, with carinate marginal stria extending posteriorly from fovea to elytral posterior margin and anteriorly to dorsal surface of elytron.

Mesoventrite short, demarcated from metaventrite by ridged anterior edges of impressed areas where lateral mesocoxal foveae situated at mesal margins, with pair of thin admesal carinae; setose median mesoventral foveae widely separated, lateral mesoventral foveae large and setose, not forked internally; intercoxal process short. Metaventrite projecting admesally, inclined toward middle, with large, setose lateral mesocoxal foveae and pair of smaller, setose lateral metaventral foveae, posterior margin emarginate at middle, lacking split.

Legs elongate; profemur ( Fig. 30D ) strongly swollen at distal 1/2, dorsal surface near apex deeply incised, with dense trichomes inside incision; mesotibia ( Fig. 30E ) with tiny, truncate protuberance at apex.

Abdomen widest at lateral margins of tergite 1 (IV), length 0.52–0.54 mm, width 0.64–0.66 mm. Tergite 1 (IV) longer than tergites 2–4 (V–VII) combined in dorsal view, setose basal sulcus separated by two mediobasal and one pair of basolateral foveae, with pair of long discal carinae, marginal carina present only at basal 1/2; tergites 2–4 (V–VII) tightly compressed, 2–3 lacking and 4 with one pair of basolateral foveae, tergite 4 shorter than 2 and 3 combined along middle, tergite 5 (VIII) semicircular, roundly emarginate at middle of posterior margin. Sternite 2 (IV) with large mediobasal and pair of broad, setose basolateral foveae, with long lateral carinae, midlength slightly longer than 3–4 (V–VI) combined, sternites 3–5 (V–VII) lacking foveae, sternite 6 (VIII) with posterior margin slightly emarginate, sternite 7 (IX) ( Fig. 30F ) slightly oval, weakly sclerotized at apical part and with few long setae along apical margin.

Aedeagus ( Fig. 30G, H ) 0.21 mm long, strongly asymmetric; median lobe with large basal capsule and subtriangular foramen, basoventral projection short, ventral stalk broad in lateral view, apex shortly forked; dorsal lobe elongate, recumbent, strongly curved and C-shaped in anterior view, apically split into two elongate lobes, upper one gradually narrowing apically, lower one forked at apex; parameres reduced to single, small membranous structure.

Female. Similar to male in external morphology; antenna shorter; each compound eye composed of approximately 21 ommatidia; humerus also angulate; legs lacking modifications. Measurements (as for male): body length 1.78–1.82 mm; length/width of head 0.36–0.37/ 0.39–0.40 mm, pronotum 0.41–0.42/ 0.42 mm, elytra 0.52/ 0.70–0.71 mm; abdomen 0.58–0.61/ 0.66–0.67 mm; length of antenna 0.88 mm; maximum width of genitalia ( Fig. 30I ) 0.22 mm.

Comparative notes. The new species is most similar to B. beibeng by the strongly swollen profemora of the male, but can be readily distinguished by the presence of a thin median carina of the vertex (lacking in B. beibeng ), the more strongly setose swollen part of the profemora, as well as by the recumbent and broader ventral stalk and the deeply split dorsal lobe of the aedeagus.

Distribution. Cona County, Tibet, SW China ( Figs 80B , 95A, B ).

Etymology. The specific epithet ‘ acclîvis (rising, sloping)’ is a Latin adjective referring to the swollen male profemora of the new species.

Figures

FIGURE 30. Morphology of Batrisiella acclivis sp. nov. (A–H. Male. I. Female). A. Dorsal habitus. B. Head and pronotum. C. Antennomere 1. D. Apical part of profemur. E. Apical part of mesotibia. F. Sternite 7 (IX). G, H. Aedeagus, anterior (G) and lateral (H). I. Genitalia. Scale bars: 0.5 mm in A; 0.3 mm in B; 0.1 mm in C–E, G–I; 0.05 mm in F.

FIGURE 80. Distribution of Tibetan Batrisini. A. Batriscenaulax campestris sp. nov. B. Batrisiella acclivis sp. nov. (circle), B. beibeng sp. nov. (triangle), B. bomea sp. nov. (square) and B. concisa sp. nov. (cross). C. B. curvitibialis sp. nov. (circle), B. ganma sp. nov. (triangle), B. guttata sp. nov. (square) and B. zhujianqingi (diamond).

FIGURE 95. Environment of and collecting sites at Lebu Valley (勒布沟). Forests at 2400 m (A, B), and 3650 m (C, D).