Arthromelodes zhentangensis, 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 : 66-68

Arthromelodes zhentangensis sp. nov.

( Figs 28 , 79C , 93E )

Chinese common name: ĿƋnjà甲

Type material (3 exx.). HOLOTYPE: CHINA: ♂ , ‘ China: Xizang, Dinggyê County, Zhêntang Town , Xiuxiongma Vill., 27°54’11”N, 87°22’42”E, 2700–3000 m, 25.vi.2021, Z. Peng, Z. Yin & W. Zhang leg., ƱẪU喀NJŤĠ 县ĿƋWšŏ玛村 ’ ( SNUC) . PARATYPES: CHINA: 1 ♂, 1 ♀, same data as that of holotype ( SNUC) .

Diagnosis. Male. Body length slightly over 2.0 mm. Head subtruncate at base; vertex lacking distinct sulcus, with long median carina, vertexal foveae moderately large and asetose; antenna relatively short, antennomeres each sub-moniliform to slightly elongate, lacking modifications. Discal stria of elytron extending to approximately apical 1/3 of elytral length. Protibia with angulate projection before apex. Abdomen with large Tergite 1 (IV) longer than tergites 2–4 (V–VII) combined in dorsal view, with central impression at posterior half. Aedeagus strongly asymmetric, ventral stalk and dorsal lobe strongly twisted or curved dorsoventrally, parameres reduced and forming single membranous structure. Female. Body length slightly over 2.0 mm, antenna and legs lacking modifications, genitalia as in Fig. 28H .

Description. Male. Body ( Fig. 28A ) length 2.06–2.08 mm; color reddish-brown, tarsi and mouthparts lighter. Dorsal surface of body covered with short pubescence.

Head ( Fig. 28B ) subtruncate at base, transverse, length 0.44 mm, width across eyes 0.50–0.51 mm; vertex mostly finely punctate, area posterior to antennal tubercle with coarse punctation, with moderately large, asetose vertexal foveae (dorsal tentorial pits), lacking distinct sulcus between antennal tubercles, long median carina extending from head base anteriorly to apex of frons, antennal tubercles weakly raised; frons convex medially, confluent with clypeus; clypeus with coarse surface, its anterior margin carinate and moderately raised; thick ocular-mandibular carina complete, carina branched below eye, extended ventrally and then anteriorly to posteroventral articulation of mandible. Venter strongly convex at apical 1/2, with gular foveae (posterior tentorial pits) in small, shared opening, with distinct median carina extending from fovea anteriorly to mouthparts. Compound eyes prominent, composed of approximately 28 moderately large ommatidia. Antenna 1.07–1.08 mm long, antennomeres 9–11 forming indistinct club; antennomere 1 thick, subcylindrical, 2 distinctly elongate, 3–8 each slightly elongate or sub-moniliform, with 7 much longer and broader than 6 and 8, 9 and 10 of similar size, moderately enlarged, 11 largest, as long as 9 and 10 combined, sub-conical.

Pronotum ( Fig. 28B ) approximately as long as wide, length 0.49–0.50 mm, width 0.50–0.51 mm, widest at middle; lateral margins rounded; disc moderately convex, finely punctate, with median longitudinal sulcus much shorter than semicircular lateral sulci in dorsal view; lacking median antebasal fovea, with complete, deep transverse antebasal sulcus connecting lateral antebasal foveae; outer and inner pair of basolateral foveae distinct, mediobasal carina short and indistinct. Prosternum with anterior part slightly longer than coxal part, with small lateral procoxal foveae; hypomeral ridge present at basal 1/2, with punctiform lateral antebasal hypomeral pit; margin of coxal cavity weakly carinate.

Elytra much wider than long, length 0.67 mm, width 0.81–0.83 mm; each elytron with two large, widely separated basal foveae, lacking subbasal fovea; humerus roundly prominent; discal stria extending from outer basal fovea to more than apical 1/3 of elytral length; subhumeral fovea absent, marginal stria extending posteriorly from basal 1/3 to apex of elytron.

Mesoventrite short, demarcated from metaventrite by ridged anterior edges of impressed areas where large, setose lateral mesocoxal foveae situated at mesal margins, with pair of admesal carinae; setose median mesoventral foveae in transverse opening, broadly separated, lateral mesoventral foveae large and setose, not forked internally. Metaventrite broadly and shallowly impressed at middle, with pair of setose lateral metaventral foveae, posterior margin with small and narrow split at middle. Longitudinal marginal stria of meso- and metaventrite complete.

Legs moderately elongate, middle and hind legs simple. Protibia ( Fig. 28C ) with roundly angulate protuberance near apex.

Abdomen slightly narrower than elytra, widest at lateral margins of tergite 1 (IV), length 0.54–0.55 mm, width 0.70–0.73 mm; lacking modifications. Tergite 1 (IV) ( Fig. 28D ) longer than tergites 2–4 (V–VII) combined; posterior half with oval, transverse and moderately deep impression at middle, anterior margin of impression with dense setae, forming setose edge; setose basal sulcus separated by mediobasal and one pair of basolateral foveae, discal carinae distinct; tergites 2–4 (V–VII) each with one pair of small basolateral foveae, tergite 4 (VII) approximately as long as 2 and 3 combined along middle, tergite 5 (VIII) semicircular, posterior margin roundly emarginate at middle. Sternite 2 (IV) with large mediobasal and broad basolateral foveae, with pair of distinct lateral carinae; midlength of sternite 2 (IV) shorter than sternites 3–5 (V–VII) combined, 3–5 each with one pair of tiny basolateral foveae, sternite 6 (VIII) transverse, posterior margin evenly curved, sternite 7 (IX) ( Fig. 28E ) roundly quadrate, weakly sclerotized, with scattered a few setae along apical margin.

Aedeagus ( Fig. 28F, G ) 0.31 mm long, strongly asymmetric; median lobe with large, expanded basal capsule and elongately oval foramen, basoventral projection short, ventral stalk in dorsal view broad and strongly twisted apically; dorsal lobe broad at base and narrowing apically, apical 1/2 strongly bent in dorsal view; parameres reduced to single membranous structure.

Female. Similar to male in external morphology; antenna slightly shorter; protibia and abdomen lacking modifications; each compound eye composed of approximately 19 ommatidia; elytra shortened, constricted at bases, humeral angle rounded. Measurements (as for male): body length 2.08 mm; length/width of head 0.43/ 0.48 mm, pronotum 0.47/ 0.48 mm, elytra 0.58/ 0.77 mm; abdomen 0.64/ 0.77 mm; length of antenna 1.01 mm; maximum width of genitalia ( Fig. 28H ) 0.31 mm.

Comparative notes. Arthromelodes zhentangensis has a transverse head that lacks a distinct sulcus on the vertex, and possesses a long median carinae on the medially convex frons. When combined with the angulate protibiae, posteriorly placed oval impression of tergite IV, and the unique form of the aedeagus of the male, the new species can be readily separated from all other members of the genus.

Distribution. Dinggyê County, Tibet, SW China ( Figs 79C , 93E ).

Etymology. The new species is named after its type locality, i. e., Zhêntang Town.

Figures

FIGURE 28. Morphology of Arthromelodes zhentangensis sp. nov. (A–G. Male. H. Female). A. Dorsal habitus. B. Head and pronotum. C. Protibia. D. Tergite 1 (IV). E. Sternite 7 (IX). F, G. Aedeagus, lateral (F) and ventral (G). H. Genitalia. Scale bars: 0.5 mm in A; 0.3 mm in B; 0.1 mm in C, F–H; 0.2 mm in D, 0.05 mm in E.

FIGURE 79. Distribution of Tibetan Batrisini. A. Arthromelodes markam sp. nov. (circle), A. monba sp. nov. (triangle) and A. nepaeformis sp. nov. (square). B. A. nepaeformis sp. nov. (circle), A. songxiaobini sp. nov. (triangle) and A. speciosus sp. nov. (square). C. A. torus sp. nov. (circle), A. zhangmu sp. nov. (triangle) and A. zhentangensis sp. nov. (square).

FIGURE 93. Environment of and collecting sites at Zhêntang Valley (ĿƋ沟). Slopes at altitudes of 3700 m (A), 4000 m (B), and 3050 m (C). D. Nadang Village (Ḅ当村). E. Road to Xiuxiongma Village (šŏ玛村). F, G. Environment of Ganma Zangbo Valley (HḼẪ布河ě). Photo Credit: F, G by Zhong Peng.