Arthromelodes lebus, 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 : 45-47

Arthromelodes lebus sp. nov.

( Figs 18 , 78C , 95A, B )

Chinese common name: 勒布njà甲

Type material ( 1 ex.). 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).

Diagnosis. Male. Body length slightly over 1.8 mm. Head sub-rectangular at base; vertexal foveae large and asetose, lacking sulcus connecting them; antenna short; antennomeres moniliform, 7 enlarged, 9 and 10 with dense short setae on mesal surface. Discal stria of elytron extending posteriorly to more than 1/5 of elytral length. Legs almost simple, only mesotibia with small apical spur. Metaventrite with dense setose area admesally. Aedeagus strongly asymmetric; median lobe with large basal capsule and rounded triangular foramen, in lateral view narrowing apically; dorsal lobe narrowing apically, with pointed apex.

Description. Male. Body ( Fig. 18A ) length 1.84 mm; color reddish-brown, head, pronotum and abdomen slightly darker than elytra, antennae and most parts of legs yellowish-brown, tarsi and mouthparts lighter. Dorsal surface of body covered with moderately long pubescence.

Head ( Fig. 18B ) sub-rectangular at base, slightly wider than long, length 0.39 mm, width across eyes 0.43 mm; vertex finely punctate, with large, asetose vertexal foveae (dorsal tentorial pits), lacking U-shaped sulcus connecting foveae or mediobasal longitudinal sulcus, with short transverse sulcus between antennal tubercles, with few large punctures lateral sulcus; antennal tubercles weakly raised; frons slightly impressed medially, confluent with clypeus; 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 large oval opening, with distinct median carina extending from foveae anteriorly to mouthparts. Eyes moderately prominent, composed of approximately 32 ommatidia. Antenna moderately short, length 0.97 mm, antennomere 7 and apical three antennomeres ( Fig. 18C ) forming distinct club; antennomere 1 thick, subcylindrical, 2–6 and 8 each moniliform, 7 strongly enlarged, 9 much larger than 8, 10 slightly short than 9, 9 and 10 with short, dense setae on mesal margin, 11 largest, slightly shorter than 9 and 10 combined, truncate at base and narrowed apically.

Pronotum ( Fig. 18B ) approximately as long as broad, length 0.47 mm, width 0.44 mm, widest at middle; lateral margins rounded; disc slightly convex, finely punctate, median longitudinal sulcus 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 or mediobasal carina, lateral antebasal foveae connected by transverse antebasal sulcus; outer and inner pair of basolateral foveae distinct. Prosternum with anterior part as long as coxal part, with small lateral procoxal foveae; hypomeral ridge present at basal 2/3, with punctiform lateral antebasal hypomeral pit; margin of coxal cavity weakly carinate.

Elytra much wider than long, length 0.64 mm, width 0.76 mm; each elytron with two large, asetose basal foveae, lacking subbasal fovea; discal stria extending from outer basal fovea to more than apical 1/5 of elytral length; humerus weakly prominent, with small subhumeral fovea, sulcate marginal stria extending from fovea to posterior margin 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, broadly forked internally; intercoxal process short. Metaventrite broadly impressed at middle, admesal areas with long, dense setae; with large, setose lateral mesocoxal foveae and pair of smaller, setose lateral metaventral foveae, posterior margin with small and narrow split at middle.

Legs moderately elongate, lacking distinct modifications; mesotibia ( Fig. 18D ) with tiny apical spur.

Abdomen widest at lateral margins of tergite 1 (IV), length 0.43 mm, width 0.69 mm. Tergite 1 (IV) in dorsal view longer than tergites 2–4 (V–VII) combined, setose basal sulcus separated by mediobasal and one pair of transverse basolateral sockets, with pair of thick discal carinae; tergites 2 and 3 (V and VI) lacking foveae, 4 (VII) as long as 2 and 3 combined along middle, with one pair of basolateral foveae, 2–4 each with pair of thin lateral carinae, tergite 5 (VIII) semicircular, posterior margin roundly emarginate at middle. Sternite 2 (IV) with large mediobasal and broad basolateral sockets, with pair of long, thick lateral carinae; midlength of sternite 2 (IV) as long as sternites 3–5 (V–VII) combined, 3 and 4 short, 5 slightly longer than 4, 3–5 lacking foveae, sternite 6 (VIII) transverse, posterior margin emarginate at middle, sternite 7 (IX) ( Fig. 18E ) slightly oval, moderately sclerotized, apex rounded and with few long setae along apical margin.

Aedeagus ( Fig. 18F, G ) 0.28 mm long, strongly asymmetric; median lobe with large basal capsule and rounded triangular foramen, ventral stalk in lateral view broad along basal 2/3 and narrowing apically; dorsal lobe elongate, broadest near middle, with pointed apex; parameres reduced to single broad membranous structure.

Female. Unknown.

Comparative notes. The new species is allied with A. crassicornis by the similar modifications of antennomeres 9 and 10, setose metaventrite, and general form of the aedeagus. These two species can be readily separated by the lack of a median longitudinal sulcus of the vertex, the strongly enlarged antennomeres 7, and a much stouter form of the aedeagus of A. lebus . The setose metaventrite is also shared with A. nepaeformis , but the male of the latter species possesses strongly sinuate protibiae and modified protarsomeres 1, which are characteristic for that species.

Distribution. Cona County, Tibet, SW China ( Figs 78C , 95A, B ).

Etymology. The new species epithet is a Latin adjective combined from ‘Lebu’ (after Lebu Valley) and suffix ‘- us (- a, - um)’ (of or from a place).

Figures

FIGURE 18. Morphology of Arthromelodes lebus sp. nov., male. A. Dorsal habitus. B. Head and pronotum. C. Antennomeres 7–11. D. Mesotibia. E. Sternite 7 (IX). F, G. Aedeagus, lateral (F) and ventral (G). Scale bars: 0.5 mm in A; 0.3 mm in B; 0.2 mm in C, D; 0.05 mm in E; 0.1 mm in F, G.

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