Arthromelodes bicolor, 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 : 17-19

Arthromelodes bicolor sp. nov.

( Figs 5 , 77B , 98C, D )

Chinese common name: ųDznjà甲

Type material ( 1 ex.). HOLOTYPE: CHINA: ♂, ‘ China: Xizang A. R., Mêdog Co., Hanmi (汗ṁ), alt. 2200 m, 19.viii.2005, TANG Liang leg.’ ( SNUC).

Diagnosis. Male. Body length slightly over 2.6 mm, head, pronotum and abdomen much darker in color than elytra. Head sub-rounded at base; vertex with transverse sinuate sulcus between antennal tubercles and long mediobasal carina, vertexal foveae large and asetose; antenna long, antennomeres each elongate, lacking modifications. Discal stria of elytron extending to apical 4/5 of elytral length. Fore and hind legs simple, mesotibia with large apical tubercle. Abdomen with tergite 1 (IV) longer than tergites 2–5 (V–VIII) combined; tergite 1 (IV) with distinct median projections near posterior margin. Aedeagus strongly asymmetric, ventral stalk broad in dorsal view, dorsal lobe strongly curved and pointed at apex, parameres reduced and forming single membranous structure.

Description. [The holotype is a squashed specimen with part of the elytra and abdomen broken] Male. Body ( Fig. 5A ) length 2.64 mm; head dark reddish-brown, pronotum and abdomen blackish-brown, elytra reddish-brown, tarsi and mouthparts light reddish-brown. Dorsal surface of body covered with moderately long pubescence.

Head ( Fig. 5B ) sub-rounded at base, approximately as broad as long, length 0.56 mm, width across eyes 0.57 mm; vertex finely punctate at center, roughly punctate posterior to antennal tubercles, with large, asetose vertexal foveae (dorsal tentorial pits), with sinuate transverse sulcus between antennal tubercles, mediobasal carina extending from head base anteriorly to sulcus, antennal tubercles weakly raised; frons broadly and shallowly impressed medially, confluent with clypeus; clypeus with sparse moderately large punctures, its anterior margin carinate and moderately raised; ocular-mandibular carina complete. Venter with single gular fovea (posterior tentorial pit), with distinct median carina extending from fovea anteriorly to mouthparts. Compound eyes prominent, composed of approximately 25 large ommatidia. Antenna lacking distinct club and modification, length 1.29 mm; antennomere 1 thick, subcylindrical, 2–11 each elongate, 11 largest, slighter longer than 9 and 10 combined, fusiform.

Pronotum ( Fig. 5B ) slightly broader than long, length 0.56 mm, width 0.59 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 distinct. Prosternum with anterior part slightly longer than coxal part, with distinct 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 0.81 mm, width 0.94 mm; each elytron with two large, asetose basal foveae, lacking subbasal fovea; humerus slightly prominent; discal stria extending from outer basal fovea to apical 4/5 of elytral length; subhumeral fovea absent, marginal stria extending from 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 moderately separated, lateral mesoventral foveae large and setose, not forked internally. Metaventrite moderately impressed at middle, with pair of setose lateral metaventral foveae, posterior margin with small and narrow split at middle.

Legs elongate, fore and hind legs simple. Mesotibia ( Fig. 5C ) with large tubercle at apex.

Abdomen narrower than elytra, widest at lateral margins of tergite 1 (IV), length 0.58 mm, width 0.86 mm. Tergite 1 (IV) ( Fig. 5D ) longest, longer than tergites 2–5 (V–VIII) combined; with broad median tubercle and one much longer but thinner projection just posterior to tubercle at posterior margin; setose basal sulcus separated by mediobasal and one pair of basolateral sockets, with pair of short discal carinae; tergites 2–5 (V–VIII) tightly compressed, tergites 2–4 (V–VII) each with one pair of basolateral foveae, tergite 5 (VIII) semicircular, posterior margin roundly emarginate at middle. Sternite 2 (IV) with mediobasal and basolateral foveae in broad setose basal impression, with pair of long lateral carinae; midlength of sternite 2 (IV) longer than sternites 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. 5E ) with weakly sclerotized, round apical part and membranous basal part.

Aedeagus ( Fig. 5F, G ) 0.43 mm long, strongly asymmetric; median lobe with large basal capsule and triangular foramen, basoventral projection short, ventral stalk broad in dorsal view and expanded at apex; dorsal lobe elongate and strongly curved, narrowing apically and pointed at apex; parameres reduced to single membranous structure.

Female. Unknown.

Comparative notes. This species can be readily recognized and separated from all other members of the genus by the large and bicolored body, as well as the tergite 1 (IV) with a median tubercle and a projection at the posterior margin and the form of the aedeagus.

Distribution. Mêdog County, Tibet, SW China ( Figs 77B , 98C, D ).

Etymology. The specific name ‘ bicolor (having two colors)’ refers to the bicolored body of the new species.

Figures

FIGURE 5. Morphology of Arthromelodes bicolor sp. nov., male. A. Dorsal habitus. B. Head and pronotum. C. Mesotibia. 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 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 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.