Triartiger jiangxinongda Yin & Du, 2024

Yin, Zi-Wei & Du, Jing-Zhe, 2024, The second species of Triartiger Kubota (Coleoptera: Staphylinidae: Pselaphinae) from China’s mainland, Zootaxa 5538 (5), pp. 479-484 : 480-483

Triartiger jiangxinongda Yin & Du , sp. nov.

Chinese common name: 江R三ỀḎm

( Figs 1 , 2 )

Type material. HOLOTYPE: CHINA: ♂, ‘China: Jiangxi, Nanchang City, Meiling , valley N Daxi sec. X004, 28°44’49”N, 115°40’22”E, 750 m, 16–28.ix.2024, FIT, J.-Z. Du leg., 梅岭X004k洗段以北山ẽ杜ḏ哲’ ( SNUC) . PARATYPE: CHINA: 1 ♂, same collection data as for holotype, except ’ 28.ix–17.x’ ( SNUC) .

Diagnosis. Male. Habitus stout, with relatively short antennae and legs. Body length 1.8–1.9 mm. Head and pronotum with granulate cuticle and covered by spatulate setae; antenna with short antennomeres 1 and 2 and long antennomere 3; 3 approximately 8.8× as long as 2. Elytra surface coarse, with distinct linear sculpture, and sparse spatulate and regular setae, posterior margin with small trichomes. Mesofemur with large triangular spine, mesotibia with small but distinct triangular spine at approximately apical 1/4 of mesal margin; metafemur with tiny ventral denticle at base. Abdomen suboval; composite tergite deeply and broadly concave at base, with pair of basolateral trichomes, disc glabrous and with short, sparse setae; paratergites 1 (IV) with broad longitudinal trichomes at bases; posterior margin of composite tergite and tergite 4 (VII) with row of sparse long, spatulate setae. Aedeagus dorsoventrally symmetric, divided into basal and apical parts; basal capsule with large ventral projection, apical lobe gradually narrowing toward apex; with membranous endophallus armature. Female. Unknown.

Description. Male. Body ( Fig. 1A ) length 1.77–1.90 mm; color reddish-brown, tarsi and mouthparts lighter in color. Most of dorsal surface of head, pronotum and elytra covered with spatulate setae, but also with regular setae on sides of head and pronotum and on disc of elytra; abdomen with sparse short setae, posterior margin with row of long spatulate setae.

Head ( Fig. 1B ) subcylindrical, moderately longer than wide, length 0.33–0.34 mm, width across eyes 0.27– 0.28 mm; vertex slightly convex, lacking foveae (dorsal tentorial pits); frons forming narrow rostrum, extending anteriorly to form vertical keel at middle; vertex and frons with coarse, granulate surface; clypeus markedly short, anterior margin with short, sparse setae. Venter with rough surface, gular region broadly and moderately impressed, tiny gular foveae (posterior tentorial pits) widely separated, lacking median carina. Compound eyes prominent, each composed of approximately 25 ommatidia. Cervical part sub-globose, dorsal surface with distinct reticulate microsculpture. Antenna ( Fig. 1C ) 0.39–0.41 mm long, lacking modifications; antennomere 1 thick and short, only partially visible dorsally, 2 as long as 1, transverse, 3 approximately 8.8× as long as 2, broadest at apical 1/4, truncate at apex.

Pronotum ( Fig. 1B ) approximately as long as wide, length 0.33 mm, width 0.34–0.35 mm, widest at middle, with coarse surface similar to that of head; lateral margins rounded at widest point, narrowing anteriorly and slightly so posteriorly; disc slightly impressed mediobasally, lacking foveae. Prosternum with anterior part longer than coxal part, with tiny, widely separated procoxal foveae; hypomera largely fused with sternum, with oblique admesal hypomeral carinae extending from anterior margin of sternum to lateral to coxal cavities.

Elytra subtrapezoidal, much wider than long, length 0.46–0.49 mm, width 0.68–0.70 mm, lacking foveae, anterior margin thickly carinate; each elytron with four to five irregular longitudinal carinae originating from base, those lateral to sutural striae complete; posterolateral margins roundly convex, each with triangular trichome ( Fig. 1A, F ). Metathoracic wings fully developed.

Mesoventrite short, fused with metaventrite, with median mesoventral foveae anterior to median keel, the latter angularly projecting at middle; pair of small lateral mesoventral foveae present. Metaventrite greatly convex at middle, descending laterally, lacking foveae, most of disc with distinct linear sculpture, broad metaventral intercoxal process widely separating coxae and broadly emarginate at middle.

Legs robust; mesofemur and mesotibia ( Fig. 1D ) each with one large and one much smaller spine on ventral and mesal margin; metafemur ( Fig. 1E ) with tiny denticle at base of ventral margin.

Abdomen slightly broader than elytra, suboval, widest at basolateral margins of composite tergite, length 0.65– 0.77 mm, width 0.72–0.73 mm. Tergite 1 (composite tergite formed by tergites IV–VI) deeply concave at base, with pair of large basolateral sockets, with trichomes ( Fig. 1D ) mesal to sockets, 2 (VII) short, transverse, with pair of small lateral nodules and foveae, 3 (VIII) transverse, roundly triangular, with pair of small basolateral foveae, posterior margin rounded. Paratergites 1 (IV) with broad longitudinal trichomes ( Fig. 1D ) at bases. Sternites with distinct sculpture, 2 (IV) broadly and deeply concave lateral to median longitudinally keeled region, lacking foveae, 3 (V) at middle as long as 4 (VI) and 5 (VII) combined, 6 (VIII) transverse, posterior margin deeply emarginate at middle, 7 (IX) composed of paired membranous plates.

Aedeagus ( Fig. 1G–I ) 0.32 mm long, dorsoventrally symmetric; median lobe divided into basal capsule and apical lobe, lacking parameres; basal capsule elongate, broadened and rounded at base, with large ventral projection and small foramen, dorsally with large oval diaphragm, apical lobe narrowing apically and in lateral view with pointed apex, with two short, tiny setae at apex; endophallus armature composed of membranous structures.

Female. Unknown.

Comparative notes. This species is morphologically most similar to the recently described T. spatulatus which is distributed in the mountainous region of Fujian, particularly in the short antennae, distinctive spatulate setae of the dorsal vestiture, and comparable spination of the middle legs. However, T. jiangxinongda sp. nov. can be distinguished by its relatively shorter head (head length/width approximately 1.2 in T. jiangxinongda vs. 1.4 in T. spatulatus ), the presence of spinose setae on the lateral margins of the head and pronotum, and on the elytral disc (spinose setae absent in T. spatulatus ), and a more slender aedeagus. Triartiger reductus Nomura , distributed on Tsushima Island, Japan, also possesses relatively short antennae but lacks the dense spatulate setae of the dorsal vestiture characteristic of T. spatulatus and T. jiangxinongda sp. nov. In addition, three congeners have been identified on Taiwan Island ( Nomura 1997c; Besuchet 2008), but these species are distinguished by their significantly longer antennae (i.e., antennae distinctly longer than head), and larger body size (2.1–2.8 mm).

Distribution. East China: Jiangxi ( Fig. 2A ).

Biology. The two males were collected using a flight intercept trap deployed in a mixed deciduous forest ( Fig. 2B, C ). Consequently, the host ant species associated with this myrmecophile remains undetermined.

Etymology. The species name is dedicated to Jiangxi Agricultural University (江ĦR业kṝ; Pinyin: Jiângxî Nóngyè Dàxué), located in Jiangxi, China, which is the current institution of the junior author. The name is a noun in apposition.

Figures

FIGURE 1. Habitus and morphological details of Triartiger jiangxinongda sp. nov. male. A. Dorsal habitus. B. Head and pronotum. C. Antenna. D. Middle leg. E. Hind leg. F. Elytral apex and abdominal base, showing trichomes. G–I. Aedeagus, dorsal (G), lateral (H) and ventral (I). Scale bars: 0.5 mm in A; 0.3 mm in B, D, E; 0.2 mm in C, F; 0.1 mm in G–I.

FIGURE 2. Distribution and habitat of Triartiger species on China’s mainland. A. Distribution of T. jiangxinongda sp. nov. and T. spatulatus (Taiwanese species are omitted on the map). B, C. Surrounding environment (B), and collection site (C) of T. jiangxinongda sp. nov.