Nipponobythus varicornis, Yin & Zeng, 2023

Yin, Zi-Wei & Zeng, Ting-Kai, 2023, Two new riparian Pselaphinae from Hubei, Central China (Coleoptera: taphylinidae), Zootaxa 5346 (3), pp. 317-324 : 320-323

Nipponobythus varicornis sp. nov.

( Figs 2 , 3 )

Chinese common name: Ƃmẅflǿffl

Type material (2 exx.). Holotype: CHINA: J, ‘China: Hubei, Xianning City , Chongyang Co., Shuikeng Vill., 29°18′22″N, 114°10′23″E, 165 m, 16-17.vii.2023, riverbank, under stone, Ting-Kai Zeng, AE ẌṪOiǥŵDzffiṁṻ ḦAEñƃäŀ ’ ( SNUC) . Paratypes: CHINA: 1 J, same collecting data as for holotype ( SNUC) .

Diagnosis. Male. Body length approximately 1.5 mm. Head truncate at base, coarsely punctate, approximately as broad as pronotum, vertex lacking modification, with moderately short mediobasal carina; frons broadly transverse; antennomeres 9 and 10 projected on dorsal surface, apical three antennomeres form distinct club. Pronotum with punctiform lateral antebasal foveae, antebasal sulcus interrupted, posterior margin of sulcus ridged, area posterior to sulcus smooth, with small impressions separated by longitudinal carinae; posterior corners weakly angulate. Metaventrite with high, setose median ridge. Legs relatively short, mesotibia with small preapical spur. Tergite 1 (IV) with broadly separated discal carinae, each carina extending posteriorly to approximately 6.5/10 of tergal length. Aedeagus moderately stout, parameres strongly asymmetric, each with two and four macrosetae on apical and lateral edges, endophallus armature composed of two elongate sclerites in basal half. Female. Unknown.

Description. Male. Body ( Fig. 2A ) length 1.51–1.52 mm; color dark reddish-brown, legs and antennae reddish-brown, tarsi and mouthparts lighter. Dorsal surface of body covered with relatively sparse pubescence.

Head ( Fig. 2B ) roundly triangular, broadly truncate at base, much wider than long, length 0.39 mm, width across eyes 0.27–0.28 mm; vertex with coarse punctures, slightly raised at middle, broadly separated foveae (dorsal tentorial pits) small and asetose, connected by shallow, reversed U-shaped impression, mediobasal carina relatively short, extending posteriorly to occipital construction and anteriorly to level below anterior margin of eyes, postocular carinae short, complete; tempora rounded, much shorter than eyes (2: 5); frons broadly transverse, shallowly impressed at middle, anteriorly fused with clypeus; clypeus smooth, short, sharply descending, with anterior margin strongly carinate and moderately raised; ocular-mandibular carinae thin, complete. Venter with rough surface; small gular foveae (posterior tentorial pits) clearly separated, with thin mediobasal carina. Compound eyes well-developed, each composed of approximately 60 ommatidia. Antenna moderately short, length 0.69 mm, with modified antennomeres 9 and 10 ( Fig. 2C ), distinct club formed by apical three enlarged antennomeres; antennomere 1 thick, subcylindrical, enlarged, 2–8 each transverse, 8 smallest, 9 subconical, dorsally with short projection and with curved tuft of setae at apex of projection, 10 much larger than 9, basal margin with broad, blunt projection, 11 largest, approximately as long as 9 and 10 combined (16:14), truncate at base, conical.

Pronotum ( Fig. 2B ) as long as wide, length 0.35 mm, width 0.37–0.38 mm, widest anterior to middle, with weakly angulate posterior corners; lateral margins rounded, convergent anteriorly and posteriorly; anterior margin slightly and smoothly curved, posterior margin evenly convex posteriorly; disc weakly convex, finely punctate, with punctiform lateral antebasal fovea, with interrupted transverse antebasal impression demarcating disc from basal collar, posterior margin of impression ridged, basal collar with smooth surface and with three pairs of moderately large impressions separated by short longitudinal ridges. Prosternum with anterior part longer than coxal part, with indistinct, narrowly separated lateral procoxal foveae; hypomeral groove complete; margins of coxal cavities non-carinate.

Elytra much wider than long, length 0.45–0.47 mm, width 0.65 mm; each elytron with two moderately large, asetose basal foveae; disc lacking obvious striae, areas posterior to outer foveae impressed for short distance; humeri weakly prominent, lacking subhumeral foveae or marginal striae; posterolateral margins with narrow clefts. Metathoracic wings fully developed.

Mesoventrite short, laterally fully fused to metaventrite; median mesoventral foveae moderately separated, originating from shared oval opening, lateral mesoventral foveae forked internally, with short, apically blunt mesoventral process; with complete marginal striae. Metaventrite with small, asetose lateral mesocoxal foveae, lacking lateral metaventral foveae, medially with greatly raised longitudinal ridge, dorsal margin of ridge densely setose, posterior margin broadly truncate at middle.

Legs moderately short; mesotibia with small preapical spur, all tibiae with row of dense setae on mesal margin at apex, mesofemur with short row of stiff setae at base of dorsal margin.

Abdomen widest at lateral margins of tergite 1 (IV), length 0.48–0.50 mm, width 0.62–0.63 mm; paratergites well-developed. Tergite 1 (IV) at middle longer than 2 (V) to 4 (VII) combined and approximately 3.6× as long as 2, basal sulcus broad and moderately deep, lateral ends with pair of small foveae, discal carinae ( Fig. 2E ) broadly separated, relatively long, extending posteriorly for 6.5/10 of tergal length; tergites 2 and 3 subequal and 4 longer than 3 at midlength, each with thin basal sulcus and lacking fovea; tergite 5 (VIII) greatly transverse, posterior margin evenly rounded. Sternite 2 (IV) at middle longer than 3–5 (V–VII) combined, with short and moderately distinct mediobasal carina, one pair of tiny basolateral foveae and one pair of large basolateral sockets, admesally with raised longitudinal lines lacking margins; sternites 3–5 at middle gradually shorter, lacking fovea, sternite 6 (VIII) ( Fig. 2F ) transverse, with pair of lateral and one median projection, median projection slightly shorter than lateral ones, sternite 7 (IX) ( Fig. 2G ) composed of pair of weakly sclerotized, lengthily elongate plates.

Aedeagus ( Fig. 2H, I ) 0.37 mm long, moderately stout, with asymmetric parameres; median lobe broadened from base toward apex; endophallus armature composed of two elongate sclerites in basal half; left paramere (orientation accordance with figure) with two macro setae along mesal and apical margins, right paramere apically extended to dorsally overlapping left one at apex, with two macrosetae on apical margin and two similar, greatly bent setae on mesal margin.

Female. Unknown.

Comparative notes. This species is easily separable from all East Asian congeners by the darkish body color, coarsely punctate head as wide as the pronotum, unique forms of the male antennal clubs and the metaventrite, long discal carinae of tergite 1 (IV), and the configuration of the aedeagus.

Biology. The two individuals were collected with Batrisiella riparia in the same sample from the same habitat ( Fig. 3 ).

Distribution. Central China: Hubei.

Etymology. The name is a combination of Latin varius (-a, -um), meaning, “different, various”, and cornis, meaning, “horned”, referring to the modified male antennal clubs of this species.

Figures

FIGURE 2. Habitus and morphological details of Nipponobythus varicornis sp. nov., male. A. Dorsal habitus. B. Head and pronotum. C. Antennomeres 8–11. D. Metaventrite, ventrolateral, showing median projection. E. Tergite 1 (IV). F. Sternite 6 (VIII). G. Sternite 7 (IX). H, I. Aedeagus, ventral. Scale bars: 0.5 mm in A; 0.2 mm in B–E; 0.1 mm in F, I.

FIGURE 3. Collecting environment and habitat of Batrisiella riparia sp. nov. and Nipponobythus varicornis sp. nov.