Arthromelodes nomurai, 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 : 56-57

Arthromelodes nomurai sp. nov.

( Figs 23 , 79B , 97C, D )

Chinese common name: Ǚ村氏njà甲

Type material ( 1 ex.). HOLOTYPE: CHINA: ♂, ‘ China: Xizang, Nyingchi City, Pailong Country , 30°0’34.71”N, 94°57’57.64”E, 2190 m, 2019.vii.15–viii.01, FIT, Z.-W. Yin leg., [ƱẪffżḦËƖǎ]’ ( SNUC).

Diagnosis. Male. Body length slightly over 2.0 mm. Head sub-rectangular at base; vertexal foveae large and asetose, with trapezoidal sulcus connecting foveae; lacking mediobasal carina; antenna moderately long, antennomeres each elongate, lacking modifications. Pronotum with median longitudinal sulcus much shorter than semicircular lateral ones. Discal stria of elytron extending to apical 1/3 of elytral length. Legs more or less robust; pro- and mesofemur thickened, mesotibia expanded mesally at basal 1/3 and with small apical protuberance, mesotrochanter with small, thin ventral spine. Abdomen with large tergite 1 (IV) longer than tergites 2–4 (V–VII) combined; tergite 1 (IV) simple; sternite 2 (IV) with short, transverse median projection. Aedeagus strongly asymmetric; median lobe with large basal capsule and rounded triangular foramen, basoventral projection moderately long, ventral stalk relatively short, narrowing apically in lateral view, dorsal lobe extremely elongate, apical half strongly curved ventrally, parameres reduced and forming single membranous structure.

Description. Male. Body ( Fig. 23A ) length 2.05 mm; color reddish-brown, tarsi and mouthparts lighter. Dorsal surface of body covered with scattered exceptionally long pubescence and normal ones.

Head ( Fig. 23B ) sub-rectangular at base, approximately as long as wide, length 0.38 mm, width across eyes 0.40 mm; vertex finely punctate, with large, asetose vertexal foveae (dorsal tentorial pits), with complete reversed trapezoidal sulcus connecting foveae, with pairs of long setae just posterior to anterior margin of sulcus and near head base, mediobasal carina absent; antennal tubercles moderately raised; frons slightly impressed medially, confluent with clypeus; clypeus with smooth surface, its anterior margin carinate and slightly raised; ocular-mandibular carina complete. Venter with single small gular fovea (posterior tentorial pit), with distinct median carina extending from fovea anteriorly to mouthparts. Compound eyes prominent, composed of approximately 30 ommatidia. Antenna distinctly clubbed and lacking modifications, length 0.90 mm; antennomere 1 thick, subcylindrical, 2–11 each elongate, 11 largest, slightly shorter than 9 and 10 combined, sub-fusiform.

Pronotum ( Fig. 23B ) slightly longer than wide, length 0.44 mm, width 0.41 mm, widest at middle; lateral margins rounded, with long thickened, erect setae scattered on lateral margins and disc; disc slightly convex, finely punctate, median longitudinal sulcus much shorter than semicircular lateral longitudinal sulci; lacking median antebasal fovea, with complete transverse antebasal sulcus connecting lateral antebasal foveae; outer and inner pair of basolateral foveae distinct. Prosternum with anterior part as long as coxal part, with distinct lateral procoxal foveae; hypomeral ridge present at basal halves, with lateral hypomeral pit; margin of coxal cavity weakly carinate.

Elytra slightly wider than long, length 0.60 mm, width 0.69 mm; each elytron with two large, asetose basal foveae; humerus weakly prominent; discal stria extending from outer basal fovea to apical 1/3 of elytral length; small subhumeral fovea present, marginal stria extending from subbase 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 admesal carinae; setose median mesoventral foveae moderately separated, lateral mesoventral foveae large and setose. Metaventrite moderately impressed at middle, with pair of setose lateral metaventral foveae, posterior margin with small and narrow split at middle.

Legs moderately elongate; pro- and mesofemur thickened; mesotrochanter with small ventral spine, mesotibia ( Fig. 23C ) expanded at basal 1/3, with small apical protuberance.

Abdomen widest at lateral margins of tergite 1 (IV), length 0.59 mm, width 0.61 mm, with scattered exceptionally long setae on dorsal surface. Tergite 1 (IV) longer than tergites 2–4 (V–VII) combined in dorsal view, lacking modifications, setose basal sulcus separated by mediobasal and one pair of broad basolateral sockets, lacking marginal or discal carinae; tergites 2–4 (V–VII) each with one pair of basolateral foveae, tergite 4 (VII) much shorter than 2 and 3 combined along middle, tergite 5 (VIII) semicircular, posterior margin roundly emarginate at middle. Sternite 2 (IV) ( Fig. 23D ) with large mediobasal foveae and transverse basolateral sockets, with pair of short lateral carinae, with short, transverse median projection near posterior margin, midlength approximately as long as 3–5 (V–VII) combined, 3–5 each with one pair of small basolateral foveae, sternite 6 (VIII) transverse, posterior margin sinuate, sternite 7 (IX) ( Fig. 23E ) with weakly sclerotized, rounded apex and few long setae along apical margin.

Aedeagus ( Fig. 23F–H ) 0.30 mm long, strongly asymmetric; median lobe short, with large basal capsule and sub-triangular foramen, basoventral projection relatively long, ventral stalk narrowing apically in lateral view, with broad apex in dorso-ventral view; dorsal lobe strongly elongate and strongly curved ventrally, with pointed apex; parameres reduced and forming single membranous structure.

Female. Unknown.

Comparative notes. Arthromelodes nomurai belongs to the A. championi group based on the aedeagal form. The new species can be readily separated from congeners by the unique modification of the mesotibia, as well as by the relatively much shorter ventral stalk of the aedeagus.

Distribution. Chagyib District (Nyingchi), Xizang, SW China ( Figs 79B , 97C, D ).

Etymology. The new species is named after the Japanese staphylinidologist Shûhei Nomura (Ǚ村周平) who described most of the species of Arthromelodes , and was the first to point out the similarity between Arthromelodes and Plocamarthrus.

Figures

FIGURE 23. Morphology of Arthromelodes nomurai sp. nov., male. A. Dorsal habitus. B. Head and pronotum. C. Mesotibia. D. Sternites 1–5 (III–VII). E. Sternite 7 (IX). F–H. Aedeagus, dorsal (F), lateral (G) and ventral (H). Scale bars: 0.5 mm in A; 0.3 mm in B; 0.2 mm in C, D, F–H; 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 97. Environment of and collecting sites at Nyingchi area. A. Sign of Yigong Tea Farm (ƌŭē厂). B. Forest near Yigong. C. Forest at Pailong Township (ḦË乡). D. Forest near Tongmai Town (ȃ9W).