Arthromelodes criniger, 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 : 28-29

Arthromelodes criniger sp. nov.

( Figs 10 , 77C , 93A, B )

Chinese common name: Ợbnjà甲

Type material (8 exx.). HOLOTYPE: CHINA: ♂, ‘ China: Xizang, Dinggyê County, pass to Zhêntang Town , 27°54’15”N, 87°32’21”E, 3650–4020 m, 27.vi.2021, Peng, Yin & Zhang, ƱẪŤĠ县ĿƋ沟Ḃ山矮杜ḁff ’ ( SNUC) . PARATYPES: CHINA: 2 ♂♂, 5 ♀♀, same data as that of holotype ( SNUC) .

Diagnosis. Male. Body length over 2.4 mm. Head subtruncate at base; median area of vertex with dense, markedly long setae oriented posteriorly, vertex with thin V-shaped sulcus between antennal tubercles and long mediobasal carina, vertexal foveae relatively small and asetose; antenna elongate, lacking modifications; antennomeres each slightly elongate, 8 smallest, 11 approximately as long as 9 and 10 combined. Discal stria of elytron thin and shallow, extending posteriorly to slightly more than half of elytral length. Fore legs simple, mesotrochanter with apically setose protuberance on ventral margin, mesotibia with short apical spine, metatrochanter with setose tuft on ventral margin. Abdomen lacking modifications, tergite 1 (IV) with long, moderately dense setae at posteromedian area, longer than tergites 2–4 (V–VII) combined. Aedeagus strongly asymmetric, median lobe with large basal capsule and elongately oval foramen, ventral stalk broad and gradually dilated at apex, dorsal lobe elongate, forked at apex, parameres reduced and forming single membranous structure. Female. Body length over 2.3 mm, legs and abdomen lacking modifications, genitalia as in Fig. 10J .

Description. Male. Body ( Fig. 10A ) length 2.43–2.46 mm; color reddish-brown, tarsi and mouthparts slightly lighter. Dorsal surface of body covered with moderately elongate pubescence.

Head ( Fig. 10B ) subtruncate at base, slightly longer than wide, length 0.52–0.53 mm, width across eyes 0.50– 0.51 mm; vertex finely punctate, with relatively small, asetose vertexal foveae (dorsal tentorial pits), with thin, V-shaped transverse sulcus between antennal tubercles, median area with dense, markedly long setae oriented posteriorly and passing posterior margin of head, mediobasal carina extending from near head base anteriorly to sulcus, antennal tubercles moderately raised; frons broadly and shallowly impressed medially, confluent with clypeus; clypeus with smooth surface, its anterior margin carinate and moderately raised; ocular-mandibular carina complete. Venter with tiny gular foveae (posterior tentorial pits) in single small pit, median carina extending from fovea anteriorly to mouthpart, gradually thickened anteriorly. Eyes moderately prominent, composed of approximately 25 ommatidia. Antenna 1.27–1.32 mm long, lacking modifications; antennomere 1 thick, subcylindrical, 2–8 each elongate, 3 and 8 of same length, shortest, 9 as long as but slightly narrower than 10, 11 largest, approximately as long as 9 and 10 combined, sub-fusiform.

Pronotum ( Fig. 10B ) as long as wide, length 0.54–0.56 mm, width 0.54–0.56 mm, widest at middle; lateral margins rounded; disc moderately convex, finely punctate, with median longitudinal sulcus slightly shorter than 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. 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 0.76–0.81 mm, width 0.84–0.87 mm, constricted at bases; each elytron with two moderately-sized, widely separated basal foveae, lacking subbasal fovea; humeral angle rounded; discal stria extending from outer basal fovea posteriorly to slightly more than half of elytral length; subhumeral fovea absent, thin marginal stria extending posteriorly from posterior middle to posterior margin 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 broadly separated, lateral mesoventral foveae large and setose, not forked internally. Metaventrite broadly impressed at middle, with pair of setose lateral metaventral foveae, posterior margin with long, narrow split at middle.

Legs elongate, fore legs simple. Mesotrochanter ( Fig. 10C ) with short, apically setose protuberance on ventral margin, mesotibia ( Fig. 10D ) with short spine at apex; metatrochanter ( Fig. 10E ) with short setose tuft on ventral margin.

Abdomen slightly narrower than elytra, widest at lateral margins of tergite 1 (IV), length 0.68 mm, width 0.75– 0.77 mm; lacking modifications. Tergite 1 ( Fig. 10F ) dorsally longer than tergites 2–4 (V–VII) combined, basal impression broken by broadly separated mediobasal and one pair of basolateral foveae, with pair of short discal carinae, with incomplete outer marginal carina; tergites 2 and 3 (V and VI) subequal in length and 4 (VII) slightly longer than 2 and 3 combined along middle, 2–4 (V–VII) each with one pair of small basolateral foveae, lateral carina of tergites 2 and 3 short, 4 complete, 5 (VIII) semicircular, posterior margin roundly and deeply emarginate at middle. Sternite 2 (IV) with two mediobasal foveae and large basolateral sockets, lacking basal impression or sulcus, with pair of short lateral carinae; midlength of sternite 2 (IV) approximately as long as 3–5 (V–VII) combined, 3–5 each with one pair of tiny basolateral foveae, sternite 6 (VIII) transverse, posterior margin broadly emarginate, sternite 7 (IX) ( Fig. 10G ) slightly oval, moderately sclerotized, apex rounded and with few long setae along apical margin.

Aedeagus ( Fig. 10H–I ) 0.35 mm long, strongly asymmetric; median lobe with large basal capsule and elongately oval foramen, basoventral projection short, ventral stalk protruding, in lateral view gradually dilated at apex; dorsal lobe obliquely erect, apically forked into two lobes; parameres reduced to single membranous structure.

Female. Similar to male in external morphology; antenna shorter; legs and abdomen lacking spines/projections or modifications; each compound eye composed of approximately 20 ommatidia; humeral angle rounded. Measurements (as for male): body length 2.33–2.48 mm; length/width of head 0.49–0.52/ 0.48–0.52 mm, pronotum 0.55–0.58/ 0.52–0.55 mm, elytra 0.69–0.75/ 0.82–0.88 mm; abdomen 0.68–0.75/ 0.74–0.83 mm; length of antenna 1.16–1.21 mm; maximum width of genitalia ( Fig. 10J ) 0.27 mm.

Comparative notes. Arthromelodes complexus is allied with A. torus and a number of species described in this paper by the similar form of the aedeagus, but can be readily separated from all of them by the dense, elongate setae that cover the central part of the vertex in both sexes.

Distribution. Dinggyê County, Tibet, SW China ( Figs 77C , 93A, B ).

Etymology. The new species name ‘ criniger (having long hair)’ is a Latin adjective suggested by long setae on the male vertex of the new species.

Figures

FIGURE 10. Morphology of Arthromelodes criniger sp. nov. (A–I. Male. J. Female). A. Dorsal habitus. B. Head and pronotum. C. Mesotrochanter. D. Apex of protibia. E. Metatrochanter. F. Tergite 1 (IV). G. Sternite 7 (IX). H, I. Aedeagus, lateral (H) and ventral (I). J. Genitalia. Scale bars: 0.5 mm in A; 0.3 mm in B; 0.2 mm in C, F; 0.1 mm in D, E, G, H–J.

FIGURE 77. Distribution of Tibetan Batrisini. A. Arthromelodes alpitorus sp. nov. (circle), A. angulatus sp. nov. (triangle) and A. aniqiao sp. nov. (square). B. A. bicolor sp. nov. (circle), A. championi (Jeannel) comb. nov. (triangle) and A. complexus sp. nov. (square). C. A. cona sp. nov. (circle), A. crassicornis sp. nov. (triangle) and A. criniger 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.