Arthromelodes intricatus, 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 : 37-38

Arthromelodes intricatus sp. nov.

( Figs 14 , 78B , 93E )

Chinese common name: Ḕúnjà甲

Type material ( 1 ex.). 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Ŀ ƋWšŏ玛村 ’ ( SNUC).

Diagnosis. Male. Body length over 2.4 mm; dorsal surface covered with long pubescence. Head subtruncate at base; vertex with transverse sulcus between antennal tubercles. Pronotum distinctly broader than head. Posterolateral areas of elytra with exceptionally long pubescence. Mesotibia with long golden setae on ventral margin; ventral surface of metatrochanter covered by dense, short setae. Tergite 1 (IV) strongly modified, composed of large central cavity of complex structures and lateral patches with dense, short setae.Aedeagus strongly asymmetric; median lobe with large basal capsule and triangular foramen, dorsal lobe protruding and forked apically.

Description. Male. Body ( Fig. 14A ) length 2.46 mm; color reddish-brown, tarsi and mouthparts lighter. Dorsal surface of body covered with long pubescence.

Head ( Fig. 14B ) subtruncate at base, approximately as long as wide, length 0.53 mm, width across eyes 0.55 mm; vertex finely punctate, with moderately large, asetose vertexal foveae (dorsal tentorial pits), with slightly curved transverse sulcus between antennal tubercles, long mediobasal carina extending from head base anteriorly to sulcus, lateral carina short, extending from near head base anteriorly to level of anterior margin of eyes; antennal tubercles moderately raised, postantennal area and frons roughly punctate; frons broadly and weakly impressed medially, confluent with clypeus; clypeus with smooth surface, its anterior margin carinate and slightly raised; ocular-mandibular carina complete, branched twice below eye, with middle carina shorter than upper and lower ones, lower carina extended ventrally and then anteriorly to posteroventral articulation of mandible. 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 23 large ommatidia. Antenna with long pubescence, lacking distinct club and modification, length 1.48 mm; antennomere 1 thick, subcylindrical, 2–11 each elongate, 11 largest, shorter than 9 and 10 combined, fusiform.

Pronotum ( Fig. 14B ) approximately as long as wide, length 0.61 mm, width 0.63 mm, widest at middle; lateral margins rounded, with dense setae at apical halves; disc slightly convex, finely punctate, with scattered long setae, median longitudinal sulcus shorter than semicircular lateral ones; lacking median antebasal fovea, mediobasal carina short, with complete transverse antebasal sulcus connecting lateral antebasal foveae; outer and inner pair of basolateral foveae distinct. Prosternum with anterior part longer than coxal part, with small lateral procoxal foveae; thick hypomeral ridge extending from base to middle of anterior part, with punctiform lateral antebasal hypomeral pit; margin of coxal cavity weakly carinate.

Elytra strongly convex, much wider than long, length 0.75 mm, width 0.89 mm, moderately constricted at bases; each elytron with two large, asetose basal foveae; humerus slightly prominent; discal stria extending from outer basal fovea to apical 1/5 of elytral length; small subhumeral fovea present, 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 admesal carinae; setose median mesoventral foveae moderately separated, lateral mesoventral foveae large and setose, not forked internally. Metaventrite broadly and shallowly impressed medially, with pair of setose lateral metaventral foveae, posterior margin with small and narrow split at middle.

Legs elongate, with meso- and metatrochanter and mesotibia weakly modified. Mesotrochanter ( Fig. 14C ) with small ventral tubercle and long golden setae on ventral margin, mesotibia with tiny tubercle at apex; metatrochanter ( Fig. 14D ) with ventral surface densely covered by short setae.

Abdomen widest at lateral margins of tergite 1 (IV), length 0.56 mm, width 0.72 mm. Tergite 1 (IV) ( Fig. 14E ) strongly modified, dorsally longer than tergites 2–4 (V–VII) combined; structure of modification complex, large central cavity with middle and basal projections, median row of dense golden setae and clustered setae at middle of raised lateral margins, area lateral to cavity sloping laterally, densely covered with short setae; setose basal sulcus separated by mediobasal and one pair of basolateral foveae, lacking distinct marginal carina; tergites 2–4 (V–VII) tightly compressed, each with one pair of basolateral foveae, tergite 4 longer than 2 and 3 combined along middle, 5 (VIII) semicircular, posterior margin roundly emarginate at middle. Sternite 2 (IV) with mediobasal foveae and large basolateral sockets, with pair of short lateral carinae; midlength of sternite 2 (IV) longer than 3–5 (V–VII) combined, sternites 3–5 each with pair of small basolateral foveae, sternite 6 (VIII) transverse, posterior margin sinuate and emarginate at middle, sternite 7 (IX) ( Fig. 14F ) with sclerotized rounded apical half and few setae along apical margin.

Aedeagus ( Fig. 14G, H ) 0.36 mm long, strongly asymmetric; median lobe with large basal capsule and foramen, basoventral projection short, ventral stalk narrowing apically, apex pointed on right side and with acute subapical projection; dorsal lobe elongate and strongly bent, deeply forked at apex; parameres reduced and forming single membranous structure.

Female. Unknown.

Comparative notes. Arthromelodes intricatus resembles A. flosculus by the elongate antennae, and a similar pattern of tergal modifications. The new species can be readily separated by the lack of a reversed U-shaped sulcus on vertex, the more strongly expanded lateral margins of the pronotum, the more elongate elytra with dense setae along the sides and posterolateral margins, and a different structure of the tergal modification and the aedeagus.

Distribution. Dinggyê County, Tibet, SW China ( Figs 78B , 93E ).

Etymology. The specific epithet ‘ intricatus ’ (intricate, complex) refers to the complicated structure of the male tergal modification of the new species.

Figures

FIGURE 14. Morphology of Arthromelodes intricatus sp. nov., male. A. Dorsal habitus. B. Head and pronotum. C. Mesotrochanter. D. Metatrochanter. E. Tergite 1 (IV). F. Sternite 7 (IX). G, H. Aedeagus, lateral (G) and ventral (H). Scale bars: 0.5 mm in A; 0.3 mm in B, C; 0.2 mm in C–E; 0.1 mm in F–H.

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 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.