Sathytes proclivis, 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 : 129-130

Sathytes proclivis sp. nov.

( Figs 56 , 84B , 95A, B )

Chinese common name: ṆƟḛà甲

Type material (13 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) . PARATYPE: CHINA: 4 ♂♂, 8 ♀♀, same data as that of holotype ( SNUC) .

Diagnosis. Male. Body length approximately 2.2 mm; ratio (length/width) of head 0.92–0.98, pronotum 1.02– 1.04, elytra 0.77–0.80, length of eye/tempus 0.90. Antennomere 9 slightly wider than long (length/width excluding apophysis 0.96), with hyaline apophysis near apex of mesal margin, antennomere 11 elongate (length/width 1.72), with weak protuberance at base, apex of protuberance with tuft of slightly curved setae. Aedeagus broadly rounded at base, slightly narrowed at middle and then broadening apically. Female. Body length approximately 2.2–2.3 mm; antenna lacking modifications, genitalia as in Fig. 56G .

Description. Male. Body ( Fig. 56A ) length 2.17–2.19 mm; color reddish-brown, tarsi and mouthparts lighter. Dorsal surface of body covered with short, dense pubescence.

Head ( Fig. 56B ) sub-rectangular at base, approximately as long as wide, length 0.47 mm, width across eyes 0.48–0.51 mm, length/width 0.92–0.98; vertex slightly raised, with small asetose foveae (dorsal tentorial pits); frons anteriorly confluent with strongly declining clypeus, shallowly impressed medially; clypeus with smooth surface, anterior margin carinate and moderately raised; ocular-mandibular carina short; postgenal region strongly projecting. Venter with small, broadly separated gular foveae (posterior tentorial pits), median carina present for anterior half. Compound eyes moderately prominent, composed of approximately 20 large ommatidia, length of eye/tempus 0.90. Antenna elongate, length 1.23–1.26 mm, distinct club ( Fig. 56C ) formed by enlarged apical three antennomeres; antennomere 1 thick, subcylindrical, 2–7 each transverse, subequal in width, 8 shorter and slightly narrower than 7, 9 ( Fig. 56D ) strongly enlarged, obliquely trapezoidal, slightly wider than long, length/width excluding apophysis 0.96, anteromesal region strongly enlarged, hyaline apophysis located near apex of mesal margin, 10 transverse, length/width 0.63, 11 largest, longer than 9 and 10 combined, length/width 1.72, with weak protuberance at base, apex of protuberance with slightly curved tuft of golden setae.

Pronotum ( Fig. 56B ) approximately as long as wide, length 0.51–0.52 mm, width 0.50 mm, length/width 1.02– 1.04, widest at middle; lateral margins rounded, convergent apically and basally; disc weakly convex; asetose lateral antebasal foveae moderately small. Prosternum with anterior part slightly longer than coxal part, with small lateral procoxal foveae; hypomeral ridge absent; margin of coxal cavity moderately carinate.

Elytra much wider than long, length 0.69–0.71 mm, width 0.89–0.90 mm, length/width 0.77–0.80; each elytron with four small, asetose basal foveae; lacking discal stria; humerus weakly prominent, acute, subhumeral fovea present, marginal stria extending from fovea to posterior margin of elytron.

Mesoventrite short, demarcated from metaventrite by strongly curved carinae; median mesoventral foveae fused at middle, originating from shared opening, large lateral mesoventral foveae shallowly forked internally, mesoventral process short, with complete marginal stria. Metaventrite weakly prominent admesally, inclined towards middle, with well-developed lateral mesocoxal and two broadly separated lateral metaventral foveae, with shallow, round median pit shortly anterior to posterior margin, posterior margin narrowly and shortly emarginate at middle.

Legs elongate, simple.

Abdomen widest at lateral margins of tergite 1 (IV), length 0.62–0.63 mm, width 0.77–0.78 mm. Tergite 1 (IV) more than twice as long as 2 (V), lacking basal sulcus, with one pair of mediobasal and two pairs of basolateral foveae, lacking discal or marginal carina; tergite 2 (V) slightly longer than 3 (VI), 4 (VII) longer than 3 but much shorter than 2 and 3 combined; tergites 2–3 (IV–VI) each with one pair of mediobasal and two pairs of basolateral foveae, 4 with one pair of basolateral foveae and marginal tubercles, 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, lateral carina absent; midlength of sternites 2–5 (IV–VII) gradually shorter, sternites 3–4 (IV–VI) each with three pairs and 5 (VII) with one pair of small basolateral foveae, sternite 6 (VIII) transverse, posterior margin broadly emarginate, sternite 7 (IX) ( Fig. 56E ) moderately sclerotized, elongate, apex with two long setae.

Aedeagus ( Fig. 56F ) 0.23 mm long, slightly asymmetric, plate-like; median lobe with large foramen, broadest at approximately apical 2/5, apical margin moderately convex at right side, with one short seta at left side.

Female. Similar to male in external morphology; antenna slightly shorter, lacking modifications; each compound eye composed of approximately 13 ommatidia; humerus faintly prominent. Measurements (as for male): body length 2.25–2.28 mm; length/width of head 0.49/ 0.47 mm, pronotum 0.51–0.53/ 0.51 mm, elytra 0.63–0.64/ 0.86– 0.87 mm; abdomen 0.73–0.75/ 0.82–0.84 mm; length of antenna 1.06–1.08 mm; maximum width of genitalia ( Fig. 56G ) 0.22 mm.

Comparative notes. The new species morphologically resembles S. longitrabis Yin & Li found in Shaanxi, central China by the obliquely expanded male antennomeres 9, but clearly differs from the latter by the more elongate antennomeres 11 which have smaller basal projections, the more strongly oblique anterior margins of antennomeres 9, and the different form of the aedeagus.

Distribution. Cona County, Tibet, SW China ( Figs 84B , 95A, B ).

Etymology. The specific epithet ‘ prôclîvis (prone, steep)’ is a Latin adjective referring to the obliquely expanded male antennomeres 9 of this species.

Figures

FIGURE 56. Morphology of Sathytes proclivis sp. nov. (A–F. Male. G. Female). A. Dorsal habitus. B. Head and pronotum. C. Antennomeres 9–11. D. Antennomere 9. E. Sternite 7 (IX). F. Aedeagus, ventral. G. Genitalia. Scale bars: 0.5 mm in A; 0.3 mm in B, C; 0.1 mm in D–G.

FIGURE 84. Distribution of Tibetan Batrisini. A. Sathytes magnus Yin & Li (circle), S. panzhaohuii Yin & Shen (triangle) and S. pengzhongi sp. nov. (square). B. S. proclivis sp. nov. (circle), S. pseudograndis sp. nov. (triangle) and S. simplex Löbl (square). C. S. sympatricus sp. nov. (circle), S. transversus Yin & Shen (triangle) and S. virupaksa sp. nov. (square).

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