Arthromelodes songxiaobini, 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 : 57-59

Arthromelodes songxiaobini sp. nov.

( Fig. 24 , 79B , 97C, D )

Chinese common name: Ṫ氏njà甲

Type material (7 exx.). HOLOTYPE: CHINA: ♂ , ‘ China: Xizang, nr. Bomê County, 29°52’22”N, 95°42’15”E, ca. 2735 m, 12.iii.2019, X.-B. Song leg., [ƱẪ波ṁ县ṉữ]’ ( SNUC) . PARATYPES: CHINA: 1 ♂, 3 ♀♀, same data as that of holotype’; 2 ♂♂ , ‘ China: Xizang, Nyingchi City, Pailong Town, Layue Bridge , 29°59’02”N, 94°52’33”E, 2550 m, 13.vii.2021, Peng leg., Ʊ Ẫffż 市ḦË乡Ń月ss桥 ’ (all paratypes in SNUC) .

Diagnosis. Male. Body length 2.01–2.24 mm. Head subtruncate at base; vertexal foveae small, asetose, lacking sulcus connecting them; antenna moderately elongate; antennomeres slightly elongate to moniliform, antennomeres 9–11 enlarged to form indistinct club. Discal stria of elytron extending to apical 1/5 of elytral length. Mesotrochanter with thin, strongly curved protuberance, mesotibia expanded mesally at basal 1/3, with curved projection at apex. Tergite 5 (VIII) with broad and deep cavity at basal 1/2, projecting at middle apically. Aedeagus strongly asymmetric; median lobe with large basal capsule and basoventral projection, ventral stalk broad in dorsal view; dorsal lobe broad at middle and narrowing both basally and apically; parameres reduced to single membranous structure. Female. Body length 1.90–1.97 mm; antenna shorter, middle legs and abdomen lacking modifications, genitalia as in Fig. 24H .

Description. Male. Body ( Fig. 24A ) length 2.01–2.24 mm; color reddish-brown, tarsi and mouthparts lighter. Dorsal surface of body covered with short pubescence.

Head ( Fig. 24B ) roundly-rectangular at base, approximately as long as wide, length 0.41 mm, width across eyes 0.42 mm; vertex finely punctate, with moderately large, asetose vertexal foveae (dorsal tentorial pits), lacking Ushaped sulcus connecting foveae or mediobasal carina, with transverse, sinuate sulcus between antennal tubercles; antennal tubercles weakly raised; frons almost flat 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) originating from shared opening, with distinct median carina extending from foveae anteriorly to mouthparts. Compound eyes prominent, composed of approximately 28 ommatidia. Antenna moderately elongate, length 0.85–0.88 mm, apical three antennomeres forming indistinct club; antennomere 1 thick, subcylindrical, 2–7 each slightly elongate, 8 smallest, moniliform, 9 much larger than 8, 10 slightly longer and broader than 9, 11 largest, as long as 9 and 10 combined, subconical.

Pronotum ( Fig. 24B ) approximately as long as broad, length 0.44–0.45 mm, width 0.45 mm, widest at middle; lateral margins rounded; disc slightly convex, finely punctate, pubescent, median longitudinal sulcus 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, 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 extending from base to middle of anterior part, with punctiform lateral antebasal hypomeral pit; margin of coxal cavity weakly carinate.

Elytra much wider than long, length 0.64–0.65 mm, width 0.76–0.77 mm; each elytron with two large, asetose basal foveae, lacking subbasal fovea; discal stria extending from outer basal fovea to 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, 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; protrochanter with small ventral tubercle; mesotrochanter with thin, long and strongly curved protuberance, mesotibia ( Fig. 24C ) expanded mesally at basal 1/3, with distinct curved projection at apex.

Abdomen widest at lateral margins of tergite 1 (IV), length 0.55–0.70 mm, width 0.70–0.71 mm. Tergite 1 (IV) longer than tergites 2–4 (V–VII) combined in dorsal view, setose basal sulcus separated by mediobasal and one pair of basolateral foveae, lacking discal carinae; tergites 2–4 (V–VII) tightly compressed, each with one pair of basolateral foveae, tergite 5 (VIII) ( Fig. 24D ) semicircle, transverse, with large central cavity at basal 1/2, inside cavity four tubercles each with one seta, posterior margin of cavity with short, dense setae, apical half of tergite projecting medially. Sternite 2 (IV) with large mediobasal foveae and pair of broad, setose basolateral sockets, midlength longer than 3–5 (V–VII) combined, 3–5 each with one pair of small basolateral foveae, sternite 6 (VIII) transverse, sternite 7 (IX) ( Fig. 24E ) with rounded apex, moderately sclerotized on apical half, membranous on basal half.

Aedeagus ( Fig. 24F, G ) 0.30 mm long, strongly asymmetric; median lobe with large basal capsule and foramen, ventral stalk short and broad in dorso-ventral view, round at apex; dorsal lobe broad at middle and narrowing both basally and apically, with pointed apex; parameres reduced to single membranous structure.

Female. Similar to male in external morphology; antenna shorter; each compound eye composed of approximately 18 ommatidia; humeral angle rounded; legs and abdomen lacking modifications. Measurements (as for male): body length 1.90–1.97 mm; length/width of head 0.39–0.41/ 0.41 mm, pronotum 0.42–0.43/ 0.43 mm, elytra 0.59/ 0.72–0.73 mm; abdomen 0.53–0.62/ 0.68–0.69 mm; length of antenna 0.80–0.81 mm; maximum width of genitalia ( Fig. 24H ) 0.26 mm.

Comparative notes. The mesally expanded mesotibiae of the male of the new species is shared only with A. nomurai . These two species can be readily separated by the medially concave male tergite 5 (VIII) and the characteristic form of the aedeagus of A. songxiaobini .

Distribution ( Fig. 96 ). Bomê County and Chagyib District (Nyingchi), Tibet, SW China ( Figs 79B , 97C, D ).

Etymology. The new species is named after Xiao-Bin Song, the collector of the holotype.

Figures

FIGURE 24. Morphology of Arthromelodes songxiaobini sp. nov. (A–G. Male. H. Female). A. Dorsal habitus. B. Head and pronotum. C. Mesotibia. D. Tergites 4 and 5 (VII and VIII). E. Sternite 7 (IX). F, G. Aedeagus, lateral (F) and ventral (G). H. Genitalia. Scale bars: 0.5 mm in A; 0.3 mm in B; 0.2 mm in C, D, F, G; 0.05 mm in E, 0.1 mm in H.

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 96. Environment of and collecting sites at Nyingchi area (ffż地区). A. Gongbo'gyamda (工布ȕḭ). B. Zhongzhe Village (ΦĖ村). C. Kading Valley (ϮŤ沟). D. Chongge Cuo (ṗẋś). E, F. A slope near Serjila mountain pass (DzĻŃ山 口). Photo Credit: A, B, E, F by Zhong Peng.

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).