Arthromelodes cona, 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 : 24-26

Arthromelodes cona sp. nov.

( Figs 8 , 77B , 95A, B )

Chinese common name: DZḄnjà甲

Type material (60 exx.). HOLOTYPE: CHINA: ♂, ‘China: Xizang, Cona County, Lebu (勒布), 27°49’10”N, 91°45’09”E, 2600 m, 19.viii.2010, leaf litter, sifted, Jian-Qing Zhu leg.’ ( SNUC) . PARATYPES: CHINA: 12 ♀♀, same data as that of holotype; 2 ♂♂, 2 ♀♀, same locality and collector, except ‘ 27°49’32”N, 91°45’35”E, 2500 m, 17.viii.2010 ’; 18 ♂♂, 25 ♀♀, same locality, except ‘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 ’ (all paratypes in SNUC) .

Diagnosis. Male. Body length over 2.2 mm. Head subtruncate at base; vertex with deep transverse sulcus between antennal tubercles and long mediobasal carina, vertexal foveae relatively small and asetose; antenna elongate, antennomeres each slightly elongate except for sub-trapezoidal antennomere 10, antennomere 11 modified with impression and ridge on ventral side. Discal stria of elytron extending to approximately apical 4/5 of elytral length. Fore and hind legs simple, mesotrochanter with long, deeply forked spine on ventral margin, mesotibia with exceptionally long apical spine. Abdomen with large Tergite 1 (IV) longer than tergites 2–4 (V–VII) combined in dorsal view, simple. Aedeagus strongly asymmetric, median lobe protruding apically, apex pointed, dorsal lobe strongly curved downwards at apical part, parameres reduced and forming single membranous structure. Female. Body length slightly over 2.0 mm, antenna and legs lacking modifications, genitalia as in Fig. 8I .

Description. Male. Body ( Fig. 8A ) length 2.29–2.35 mm; color reddish-brown, tarsi and mouthparts lighter. Dorsal surface of body covered with moderately long pubescence.

Head ( Fig. 8B ) subtruncate at base, approximately as long as wide, length 0.49–0.51 mm, width across eyes 0.51–0.52 mm; vertex finely punctate, with relatively small, asetose vertexal foveae (dorsal tentorial pits), with curved deep, slightly sinuate transverse sulcus between antennal tubercles, mediobasal carina extending from head base anteriorly to sulcus, antennal tubercles moderately raised; frons broadly and shallowly impressed medially, confluent with clypeus; clypeus with smooth surface, its anterior margin carinate and moderately raised; ocularmandibular 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 25 moderately large ommatidia. Antenna 1.26–1.32 mm long, with modified antennomeres 10 and 11 ( Fig. 8C ); antennomere 1 thick, subcylindrical, 2–9 each elongate, 10 transverse, sub-trapezoidal, 11 large, slightly longer than 9 and 10 combined, ventral surface with oblique carina demarcating broadly impressed area, dorsal surface with mesal margin round-angularly expanded mesally.

Pronotum ( Fig. 8B ) approximately as long as wide, length 0.50–0.53 mm, width 0.53 mm, widest at middle; lateral margins rounded; disc moderately convex, finely punctate, with median longitudinal sulcus as long as semicircular lateral sulci in dorsal view; lacking median antebasal fovea, with complete, deep 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 small 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 0.73–0.76 mm, width 0.88–0.91 mm; each elytron with two large, widely separated basal foveae, lacking subbasal fovea; humerus weakly prominent; discal stria extending from outer basal fovea to apical 4/5 of elytral length; subhumeral fovea small, marginal stria extending posteriorly from middle 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 broadly separated, lateral mesoventral foveae large and setose, 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. Mesotrochanter ( Fig. 8D ) with long, deeply forked spine at base, mesotibia ( Fig. 8E ) with large blade-like spine at apex.

Abdomen slightly narrower than elytra, widest at basolateral margins of tergite 1 (IV), length 0.56–0.58 mm, width 0.78–0.79 mm; lacking modifications. Tergite 1 (IV) longer than tergites 2–4 (V–VII) combined; setose basal sulcus separated by mediobasal and one pair of basolateral foveae, with pair of short 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) with large mediobasal and broad basolateral sockets in setose basal impression, with pair of short, triangular lateral carinae; midlength of sternite 2 (IV) longer than sternites 3–5 (V–VII) combined, 3–5 each with one pair of tiny basolateral foveae, sternite 6 (VIII) transverse, posterior margin sinuate, sternite 7 (IX) ( Fig. 8F ) slightly oval, moderately sclerotized, apex rounded and with few long setae along apical margin.

Aedeagus ( Fig. 8G, H ) 0.47 mm long, strongly asymmetric; median lobe with large basal capsule and sub-triangular foramen, basoventral projection moderately long, ventral stalk protruding and pointed at apex; dorsal lobe elongate and strongly curved downwards apically, gradually narrowing towards apex; parameres reduced to single membranous structure.

Female. Similar to male in external morphology; antenna shorter; antenna and legs lacking modifications; each compound eye composed of approximately 20 ommatidia; humeral angle rounded. Measurements (as for male): body length 2.20–2.22 mm; length/width of head 0.47–0.48/ 0.47–0.49 mm, pronotum 0.50–0.51/ 0.51–0.52 mm, elytra 0.62–0.67/ 0.84–0.86 mm; abdomen 0.58–0.59/ 0.77–0.79 mm; length of antenna 0.98–0.99 mm; maximum width of genitalia ( Fig. 8I ) 0.27 mm.

Comparative notes. Arthromelodes cona is placed as a member of the A. championi group based on the aedeagal form. The new species can be readily separated from all members of the group, except for A. abdominalis , by the male’s unique antennal modifications, the large, blade-like spine of the mesotibia, as well as the form of the aedeagus. Arthromelodes abdominalis was described based on a single female, and its identity remains elusive until an associated is made available. However, it appears to be unlikely that A. abdominalis and A. cona represent the same species given the larger body size (2.6 mm vs. 2.20–2.22 mm) and V-shaped frontal sulcus (slightly sinuate in A. cona ) of the former species, as well as their widely separated distributions.

Distribution. Cona County, Tibet, SW China ( Figs 77B , 95A, B ).

Etymology. The species is named after Cona County, where its type locality is situated.

Figures

FIGURE 8. Morphology of Arthromelodes cona sp. nov. (A–H. Male. I. Female). A. Dorsal habitus. B. Head and pronotum. C. Antennomeres 9–11. D. Mesotrochanter. E. Mesotibia. F. Sternite 7 (IX). G, H. Aedeagus, dorsal (G) and lateral (H). I. Genitalia. Scale bars: 0.5 mm in A; 0.3 mm in B, E; 0.2 mm in C, G, H; 0.1 mm in D, I, F.

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