Arthromelodes lage, 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 : 39-40

Arthromelodes lage sp. nov.

( Fig. 15 , 78B , 98A, B )

Chinese common name: Ń格njà甲

Type material ( 1 ex.). HOLOTYPE: CHINA: ♂, ‘ China: Xizang A. R., Mêdog County, Lage (ca 5.5 km E Dochula Pass, 29°28’12”N, 94°59’22”E), 3000–3500 m, 11.viii.2005, Liang Tang leg., [ƱẪẸṘ县Ń格]’ ( SNUC).

Diagnosis. Male. Body length 2.6 mm. Head rounded at base; vertex with transverse V-shaped sulcus between antennal tubercles, vertexal foveae asetose and small; antenna long and slender, antennomeres each slightly elongate, lacking modifications. Discal stria of elytron extending to approximately half of elytral length. Protibia expanded at middle; mesotrochanter with tufted golden setae on ventral margin. Abdomen with large tergite 1 (IV) longer than tergites 2–4 (V–VII) combined; tergite 1 (IV) with broad and deep central cavity and laterally impressed. Aedeagus strongly asymmetric, ventral stalk of median lobe protruding, apex membranous, dorsal lobe strongly curved at apex, parameres reduced and forming single membranous structure.

Description. Male. Body ( Fig. 15A ) length 2.60 mm; color reddish-brown, tarsi and mouthparts paler. Dorsal surface of body covered with moderately long pubescence.

Head ( Fig. 15B ) rounded at base, slightly broader than long, length 0.51 mm, width across eyes 0.57 mm; vertex finely punctate, with relatively small, asetose vertexal foveae (dorsal tentorial pits), with V-shaped sulcus between antennal tubercles, mediobasal carina relatively long, distinct, extended from posterior margin of vertexal sulcus towards near head base, antennal tubercles strongly raised; frons broadly impressed medially, confluent with clypeus at middle; clypeus with smooth surface, its anterior margin carinate and moderately raised; ocular-mandibular carina complete. Venter with two small gular foveae (posterior tentorial pits) in single pit, with thin median carina extending from fovea anteriorly to mouthparts. Compound eyes prominent, composed of approximately 25 small ommatidia. Antenna lacking modification, length 1.38 mm, club loosely formed by antennomeres 9–11; antennomere 1 thick, subcylindrical, 2–11 each elongate, 11 largest, approximately as long as 9 and 10 combined, sub-fusiform.

Pronotum ( Fig. 15B ) slightly longer than wide, length 0.58 mm, width 0.53 mm, widest at middle; lateral margins rounded; disc slightly convex, finely punctate, with median longitudinal sulcus as long as semicircular lateral sulci in dorsal view; lacking median antebasal fovea, with complete transverse antebasal sulcus connecting lateral antebasal foveae; outer and inner pair of basolateral foveae small. Prosternum with anterior part approximately as long as coxal part, with small lateral procoxal foveae; hypomeral ridge present at basal 1/2, with indistinct lateral antebasal hypomeral pit; margin of coxal cavity weakly carinate.

Elytra much wider than long, length 0.75 mm, width 0.88 mm; each elytron with two medium-sized, asetose basal foveae, lacking subbasal fovea; humerus slightly prominent; discal stria extending from outer basal fovea to approximately half of elytral length; lacking subhumeral fovea, marginal stria extending posteriorly from basal 1/4 to apex.

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 moderately separated, lateral mesoventral foveae large and setose, not forked internally. Metaventrite weakly impressed at middle, with pair of setose lateral metaventral foveae at middle; posterior margin with small, narrow split at middle.

Legs elongate. Protibia expanded from basal 1/3 to near apex; mesotrochanter ( Fig. 15C ) with long tufted golden setae on ventral margin.

Abdomen slightly narrower than elytra, widest at basolateral margins of tergite 1 (IV), length 0.69 mm, width 0.85 mm. Tergite 1 (IV) ( Fig. 15D ) strongly modified, with broad, deep central cavity, anterior margin of cavity strongly carinate, posterior margin with narrow projection at middle, inside central cavity another ‘∞’-shaped cavity with densely setose anterior margin, areas lateral to cavity strongly impressed and smooth; setose basal sulcus separated by mediobasal and one pair of basolateral foveae, with thick, triangular discal carinae; tergites 2–4 (V–VII) each with one pair of basolateral foveae, tergite 4 (VII) as long as 2 and 3 combined along middle, tergite 5 (VIII) semicircular, posterior margin roundly emarginate at middle. Sternite 2 (IV) lacking basal sulcus, with large mediobasal and two pairs of basolateral foveae, with pair of distinct lateral carinae; midlength of sternite 2 (IV) as long as 3–5 (V–VII) combined, sternites 3–5 approximately subequal in length along midline, each with one pair of small basolateral foveae, sternite 6 (VIII) transverse, posterior margin sinuate, sternite 7 (IX) ( Fig. 15E ) with weakly sclerotized, rounded apex and few long setae along apical margin.

Aedeagus ( Fig. 15F, G ) 0.35 mm long, strongly asymmetric; median lobe with large basal capsule and foramen, with short basoventral projection, ventral stalk strongly protruding, apex in dorsal view expanded; dorsal lobe in lateral view broader than apical part of median lobe, strongly curved in dorso-ventral view; parameres reduced to single membranous structure.

Female. Unknown.

Comparative notes. Arthromelodes lage is similar to A. angulatus in the location of the central cavity and lateral impressed areas of male tergite 1 (IV), as well as the form of the aedeagus in ventral view. Arthromelodes lage can be readily separated from the latter species by the expanded male protibiae (slender in A. angulatus ), the presence of tufted setae at the ventral margin of the mesotrochanter (lacking in A. angulatus ), the different structures of the abdominal modifications, and a relatively much less protruding median lobe of the aedeagus. The new species is also similar to A. aniqiao , but can be separated by the expanded male protibiae and a different shape of the median lobe of the aedeagus.

Distribution. Mêdog County, Tibet, SW China ( Figs 78B , 98A, B ).

Etymology. The specific epithet is taken from ‘Lage’, type locality of the new species.

Figures

FIGURE 15. Morphology of Arthromelodes lage sp. nov., male. A. Dorsal habitus. B. Head and pronotum. C. Mesotrochanter and mesofemur. D. Tergite 1 (IV). E. Sternite 7 (IX). F, G. Aedeagus, lateral (F) and ventral (G). Scale bars: 0.5 mm in A; 0.3 mm in B, D; 0.2 mm in C, F, G; 0.1 mm in E.

FIGURE 78. Distribution of Tibetan Batrisini. A. Arthromelodes cylindricus sp. nov. (circle), A. flosculus sp. nov. (triangle) and A. gyamda sp. nov. (square). B. A. intricatus sp. nov. (circle), A. lage sp. nov. (triangle) and A. langjicuo sp. nov. (square). C. A. latithorax sp. nov. (circle), A. lebus sp. nov. (triangle) and A. lotus sp. nov. (square).

FIGURE 98. Environment of and collecting sites at Nyingchi area. A, B. Lage (Ń格). C, D. Hanmi (汗ṁ). E, F. Aniqiao (Nj 尼桥). Photo Credit: A, B by Chao Wu; C, D by Wen-Xuan Bi; E, F by Hao Huang.