Stenothemus gracilis Y. Yang & X. Yang, 2021

Yang, Yuxia, Ge, Shujuan, Yang, Xingke & Liu, Haoyu, 2021, Taxonomic revision of the species of Stenothemus from Southwest China (Coleoptera, Cantharidae), with the descriptions of five new species, European Journal of Taxonomy 757 (1), pp. 1-36 : 21-24

Stenothemus gracilis Y. Yang & X. Yang sp. nov.

urn:lsid:zoobank.org:act:FC569AB0-1536-4CFF-8A47-AB758A67F21D

Figs 6G‒I , 7D , 9A , 12B

Differential diagnosis

This new species is most similar to S. limbatipennis ( Pic, 1926) , but can be distinguished by the following characters: antennomeres IV‒XI each with a small oval impression in middle of outer edge in male (with longitudinal impressions in S. limbatipennis ); pronotum about 1.3 times as long as wide (while nearly as long as wide in S. limbatipennis ); aedeagus: ventral process of each paramere moderately bent ventrally in lateral view, middle emargination between dorsal plates longer than half its length, laterophyses clearly exceeding middle emargination (while ventral process strongly bent ventrally, middle emargination between dorsal plates shorter, apex of laterophyses just reaching in S. limbatipennis , see Yang et al. 2021: figs 3g ‒i); abdominal sternite VIII: lateroapical angles triangular and protruding, posterior margin rectangularly emarginate in middle, membrane strongly sclerotized and triangularly bilobed at apex (lateroapical angles widely rounded, middle emargination rounded, membrane weakly sclerotized and tapered at apex in S. limbatipennis , see Yang et al. 2021: fig. 8c); female internal organ of reproductive system: diverticulum obviously longer than spermatheca (while shorter in S. limbatipennis , see Yang et al. 2021: fig. 6c).

Etymology

The specific name is derived from the Latin ‘ gracilis ’ (‘slender’), referring to its slender body.

Material examined

Holotype

CHINA • ♂; Hubei, Shennongjia, Dongxi ; 31º34′15′′ N, 110º08′47′′ E; 819 m a.s.l.; 7‒10 Jul. 2014; Y.B. Ba and S.Y. Tang leg.; MHBU HBU(E) 410022 .

Paratypes

CHINA ‒ Gansu • 2 ♂♂; Wenxian, Liujiaping ; 2100 m a.s.l.; 27 Jun. 1998; X.K. Yang leg.; IZAS IOZ(E) 225790 , 225791 . ‒ Guizhou • 1 ♂; Daozhen, Yangxi, Shadang ; 31 May 2004; Y.Yu leg.; MHBU HBU(E) 410027 . ‒ Hubei • 1 ♂; Shennongjia, Dongxi ; 31º34′15′′ N, 110º08′47′′ E; 819 m a.s.l.; 7‒10 Jul. 2014; Y.B. Ba and S.Y. Tang leg.; MHBU HBU(E) 410023 • 1 ♂, 1 ♀; Shennongjia, Pingqian ; 31º28′08.0′′ N, 110º02′23.4′′ E; 1576 m a.s.l.; 4‒7 Jul. 2014; Y.B. Ba and S.Y.Tang leg.; MHBU HBU(E) 410024 , 410025 • 1 ♂; Shennongjia, Wenshui Forest Farm; 12 Jul. 2018; P. Wang leg.; MHBU HBU(E) 410026 • 1 ♂; Shennongjia, Songluo ; 900 m a.s.l.; 14 Jun. 1981; Y.H. Han leg.; IZAS IOZ(E) 225781 . ‒ Sichuan • 1 ♂; Wushan, Liziping ; 1870 m a.s.l.; 2 Jul. 1993; W.Z. Li leg.; IZAS IOZ(E) 225782 • 2 ♂♂; same collection data as for preceding; 3 Jul. 1993; W.Z. Li leg.; IZAS IOZ(E) 225783 , 225784 • 2 ♂♂, 1 ♀; same collection data as for preceding; R.Z. Huang leg.; IZAS IOZ(E) 225785 to 225787 • 2 ♂♂; same collection data as for preceding; 4 Jul. 1993; R.Z. Huang leg.; IZAS IOZ(E) 225788 , 225789 .

Description

Body length (both sexes): 5.0‒ 7.2 mm (5.8 mm in holotype); width: 0.5‒1.0 mm (0.7 mm in holotype).

Male ( Fig. 9A )

COLORATION. Body brown, clypeus, mouthparts, posterior margins of abdominal ventrites lightly yellow. Body densely covered with short, semi-erected pale pubescence.

HEAD. Subquadrate, surface densely and finely punctate, each side with a smooth and rectangular impression behind antennal socket; eyes strongly protruding, head width across eyes 1.6 times wider than pronotum; terminal maxillary palpomeres long-triangular, widest in middle; antennae filiform, extending to ¾ length of elytra, antennomeres II about twice times as long as wide at apices, III about 1.8 times longer than II, IV‒XI each with a small and smooth oval impression in middle of outer edge, VII longest, XI slightly longer than X, pointed at apex.

PRONOTUM. Subquadrate, about 1.3 times as long as wide, anterior margin slightly arcuate, anterior angles obtuse, sub-rectangular, lateral margins nearly parallel and slightly sinuate, posterior margin slightly arcuate and narrowly bordered, posterior angles sub-rectangular, disc distinctly convex on posterolateral parts, surface finely and densely punctate.

ELYTRA. Nearly parallel-sided, about 3.8 times as long as humeral width, 4.9 times longer than pronotum, surface finely and densely punctate, with hardly visible longitudinal costae present.

AEDEAGUS ( Fig. 6G‒I ). Moderately swollen laterally in basal part, reduced apically in diameter; basal piece nearly as long as dorsal plate of each paramere, with a small, bifurcate conjoined middle nodule at base of ventral side; ventral processes of parameres approaching each other, short and slightly thickened apically, bent ventrally in lateral view; dorsal plates slightly longer than ventral processes, strongly narrowed near base, approaching each other, apex acute and directed ventrally; apical parts of laterophyses depressed and separated from each other, apex rounded and bent dorsally, clearly exceeding middle emargination between dorsal plates.

Female

Similar to male, but body stouter than male, eyes small, less protruding, head width across eyes 1.2 times wider than pronotum, antennae shorter and roughly extending to elytral mid-length, IV‒XI without smooth oval impressions; pronotum wider, nearly as long as wide; elytra about 3.3 times as long as humeral width.

ABDOMINAL STERNITE VIII ( Fig. 7D ). Strongly narrowed posteriorly, lateroapical angles triangular and protruding, posterior margin widely and rectangularly emarginate in middle and feebly sinuate on both sides, behind the notch with a membrane which is sclerotized and triangularly bilobed at apex, with a rectangular sclerite present at center and a small longitudinal sclerite on each side.

INTERNAL ORGAN OF REPRODUCTIVE SYSTEM ( Fig. 12B ). Vagina stout, with median oviduct situated at ventroapical part, vagina abruptly narrowed in apical part and extended into a short duct which diverticulum and spermathecal duct are arising from; diverticulum extremely long, about 0.86 times adult body length, evenly thinned apically, slender tube-shaped and spiral; spermathecal duct much shorter than diverticulum; spermatheca slender tube-shaped and spiral, obviously thinner than spermathecal duct and much shorter than diverticulum, with basal part extended into a short tube, at opening of accessory gland. Accessory gland thin in basal part and the remainder thick, obviously shorter than spermatheca.

Variation within species

Head sometimes with yellow markings behind eyes, pronotum more or less lightened on posterolateral parts, elytra sometimes yellow at humeri and bases of outer margins.

Distribution

China (Hubei, Sichuan, Gansu, Guizhou).

Figures

Fig. 6. Aedeagus (A, D, G = ventral view; B, E, H = dorsal view; C, F, I = lateral view).A‒C. Stenothemus grahami Wittmer, 1974 (MHBU, Henan). D‒F. S. minutissimus (Pic, 1933) comb. nov. (IZAS, Sichuan). G‒I. S. gracilis Y. Yang & X. Yang sp. nov. (MHBU HBU(E) 410022). Scale bars = 0.5 mm.

Fig. 7. Abdominal sternite VIII of female, ventral view. A. Stenothemus minutissimus (Pic, 1933) comb. nov. (IZAS, Sichuan). B. S. tryznai Švihla, 2004 (IZAS, Sichuan). C. S. singularicollis (Pic, 1933) comb. nov. (MHBU, Shaanxi). D. S. gracilis Y. Yang & X. Yang sp. nov., paratype (IZAS IOZ(E) 225787). E. S. flavicollis Y. Yang & S. Ge sp. nov., paratype (MHBU HBU(E) 410039). F. S. laticornis Y. Yang & H. Liu sp. nov., paratype (MHBU HBU(E) 410047). Scale bars = 1.0 mm.

Fig. 9. Habitus, dorsal view. A. Stenothemus gracilis Y. Yang & X. Yang sp. nov., holotype, ♂ (MHBU HBU(E) 410022).B. S. chongqingensisY.Yang & H. Liusp. nov., holotype, ♂ (MHBU HBU(E) 410028). C. S. flavicollis Y. Yang & S. Ge sp. nov., holotype, ♂ (MHBU HBU(E) 410029). D. S. jindraimimus Y. Yang & X. Yang sp. nov., holotype, ♂ (IZAS IOZ(E) 1389239). E. S. laticornis Y. Yang & H. Liu sp. nov., holotype, ♂ (MHBU HBU(E) 410045). Scale bars = 1.0 mm.

Fig. 12. Female reproductive system, ventral view. A. Stenothemus singularicollis (Pic, 1933) comb. nov. (MHBU, Shaanxi). B. S. gracilis Y. Yang & X. Yang sp. nov., paratype (IZAS IOZ(E) 225787). C. S. flavicollis Y. Yang & S. Ge sp. nov., paratype (MHBU HBU(E) 410039). D. S. laticornis Y. Yang & H. Liu sp. nov., paratype (MHBU HBU(E) 410047). Abbreviations: see Material and methods. Scale bars = 0.5 mm.