Batrisocenus asper, Zhang & Yin, 2025

Zhang, Yong-Qin & Yin, Zi-Wei, 2025, The ant-like litter beetle fauna from the Wumenshan National Nature Reserve, China, with description of eight new species (Staphylinidae: Pselaphinae), European Journal of Taxonomy 1007, pp. 133-162 : 144-147

Batrisocenus asper sp. nov.

Chinese common name: 粗糙隆ẘü甲 urn:lsid:zoobank.org:act:8F10A035-1841-4420-BAB9-DA55AA584D55 Fig. 4

Diagnosis

Male

Body elongate, length approximately 2.0 mm. Head and pronotum with coarse punctation. Head subrectangular; vertex with complete, shallow U-shaped sulcus connecting relatively small, asetose vertexal foveae. Antenna elongate, antennomeres more or less elongate, lacking modifications; antennomere 11 approximately as long as 9 and 10 combined. Discal striae of elytra extending to approximately apical ¾ of elytral length. Protibia triangularly expanded on apicomesal margin; mesotibia with distinct apical denticle. Abdomen with large tergite 1 (IV) longer than tergites 2–4 (V– VII) combined in dorsal view, posteriorly with posteromedial cavity and oval, setose lateral patches. Aedeagus strongly asymmetric, ventral stalk much longer than dorsal lobe, dorsal lobe greatly curved, parameres reduced and forming large membranous structure.

Female

Body length approximately 1.9 mm; legs simple, genitalia as in Fig. 4I .

Etymology

The name is derived from the Latin adjective ‘ asper ’, meaning ‘rough’, ‘coarse’. This refers to the coarsely punctate head and pronotum of this species. The name is an adjective in the masculine singular nominative form.

Type material

Holotype

CHINA • ♂; Yunnan, Zhaotong City, Wumengshan Conservation Area, Miaoshan , Xiaocaoba ; 27°29′33″ N, 104°10′19″ E; 1709–1800 m a.s.l.; 20 Jul. 2022; Wei leg.; Ǖ南昭ª市乌®山小ẽữ, 魏 ǡ豪*; SNUC.

Paratypes

CHINA • 3 ♂♂, 1 ♀; same data as for holotype; SNUC .

Description

Male

BODY ( Fig. 4A ). Length 2.00– 2.01 mm; head, pronotum and abdomen dark reddish-brown, elytra and legs reddish-brown, tarsi and mouthparts lighter in colour. Dorsal surface of body covered with short pubescence.

HEAD ( Fig. 4B ). Subrectangular, truncate at base, wider than long, length 0.39 mm, width 0.47 mm; vertex coarsely punctate, with relatively small, asetose vertexal foveae (dorsal tentorial pits), with complete, shallow U-shaped sulcus connecting foveae, with thin mediobasal carina extending from base to level of eye midlength; tempora much shorter than eyes, convergent posteriorly; antennal tubercles moderately raised; frons slightly impressed medially, confluent with clypeus; clypeus with coarse surface, its anterior margin carinate and moderately raised; ocular-mandibular carinae complete, distinct. Venter with small gular foveae (posterior tentorial pits) in single pit, with distinct median carina extending from pit anteriorly to mouthparts. Compound eyes prominent, composed of approximately 35 ommatidia. Maxillary palpus with palpomere 1 minute, 2 elongate, curved, pedunculate basally and enlarged apically, 3 short, subtrapezoidal, 4 fusiform, widest near middle. Antenna moderately elongate, length 1.11–1.12 mm; club loosely formed by enlarged apical three antennomeres; antennomere 1 thick, subcylindrical, 2–7 each elongate, successively longer, 8 shortest, 9 much longer and broader than 8, 10 shorter than 9, 11 longest, approximately as long as 9 and 10 combined (22:23), subfusiform.

PRONOTUM ( Fig. 4B ). Slightly wider than long, length 0.44–0.47 mm, width 0.47–0.51 mm, widest slightly anterior to middle; lateral margins rounded; disc moderately convex, coarsely punctate, with median longitudinal sulcus slightly longer than 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 punctiform. Prosternum with basisternal (precoxal) portion longer than procoxal rests; with small lateral procoxal foveae; hypomeral grooves obliquely extending from base anteriorly to half-length of hypomera, with lateral antebasal hypomeral impressions, hypomeral ridges close to margins of coxal cavities.

ELYTRA. Slightly wider than long, length 0.65–0.69 mm, width 0.78 mm; moderately constricted and truncate at bases; each elytron with two tiny, asetose basal foveae; discal striae long, curved, extending from outer basal foveae posteriorly to 7.7 /10 of elytral length; humeri distinctly raised, small subhumeral foveae present, thin marginal striae extending posteriorly from foveae to posterior margins of elytra. Metathoracic wings fully developed.

MESOVENTRITE. Short, laterally fully demarcated from metaventrite by oblique ridges; median mesoventral foveae widely separated, originating from shared setose, transverse opening, lateral mesoventral foveae large and setose, broadly forked internally; prepectus massive, collar-shaped; mesoventral intercoxal process short, apically acute; marginal striae complete. Metaventrite weakly impressed at middle, with large, setose lateral mesocoxal foveae and pair of tiny lateral metaventral foveae, metaventral intercoxal process with loop-shaped notch at middle.

LEGS. Moderately elongate; protibia triangularly projected and with apical trichome on apicomesal margin ( Fig. 4C ); profemur widened to middle; mesotibia with distinct apical denticle ( Fig. 4D ).

ABDOMEN. Slightly narrower than elytra, widest at lateral margins of tergite 1 (IV), length 0.57–0.60 mm, width 0.67–0.71 mm; tergite 1 (IV) ( Fig. 4E ) strongly modified, longer than tergites 2–4 (V–VII) combined; posterior portion with broad central cavity, anterior margin with pair of trichomes, with large, greatly prominent projection at middle; areas lateral to cavity impressed and forming setose patched; setose basal sulcus separated by mediobasal and one pair of basolateral foveae, with 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 one mediobasal foveae and three basolateral foveae, lacking basal impression or sulcus; midlength of sternite 2 (IV) as long as sternites 3–5 (V–VII) combined, 3–5 each lacking basolateral foveae, sternite 6 (VIII) transverse, posterior margin sinuate, sternite 7 (IX) ( Fig. 4F ) suboval, weakly sclerotized, with scattered long setae along apical margin.

AEDEAGUS ( Fig. 4G–H ). 0.33 mm in length, moderately sclerotized, dorso-ventrally strongly asymmetric; median lobe with relatively small basal capsule and round foramen, ventral stalk narrow and elongate, curved at basal 2 /5, narrowing toward apex; dorsal lobe strongly bent at approximately middle, broadened in lateral view, with narrowed apex; parameres reduced to single broad membranous structure.

Female

Similar to male in external morphology; antenna shorter; legs and abdomen lacking spines or projections; each compound eye composed of approximately 30 ommatidia; humeral angles of elytra rounded; metathoracic wings absent. Measurements (as for male): body length 2.01 mm; length/width of head 0.39/ 0.48 mm, pronotum 0.44/ 0.48 mm, elytra 0.63/ 0.77 mm; abdomen 0.72/ 0.72 mm; length of antenna 1.01 mm; genitalia ( Fig. 4I ) slightly sclerotized, greatly transverse, maximum width 0.27 mm.

Remarks

A similar species occurring in a cave environment has been described from Sichuan ( Yin & He 2020), sharing a small trichome at the apex of the protibia. Batrisocenus asper sp. nov. is an epigean species that lacks the adaptive traits typically associated with cave-dwelling beetles, e.g., exceptionally elongate appendages. This species can be readily distinguished from its cavernicolous counterparts by the coarsely punctate head and pronotum, the specific shape of the modifications on the male first tergite, and the unique form of the aedeagus.

Distribution

Southwest China: Yunnan.

Figures

Fig. 4. Batrisocenus asper sp. nov. A–H. Holotype, ♂ (SNUC). I. Paratype, ♀ (SNUC). A. Dorsal habitus. B. Head and pronotum. C. Protibia. D. Mesotibia. E. Tergite 1 (IV). F. Sternite 7 (IX). G. Aedeagus, lateral view. H. Aedeagus, ventral view. I. Genitalia, ventral view. Scale bars: A = 0.5 mm; B = 0.3 mm; C–E = 0.2 mm; F = 0.05 mm; G–I = 0.1 mm.