A review of the genus Sinocymbachus Strohecker & Chûjô with description of four new species (Coleoptera, Endomychidae)

Abstract This work presents a review of species of the Asian genus Sinocymbachus Strohecker & Chûjô, 1970. Four new species are described from China: S. fanjingshanensis Chang & Bi, sp. nov., S. longipennis Chang & Bi, sp. nov., S. sinicus Chang & Bi, sp. nov., and S. wangyinjiei Chang & Bi, sp. nov.Cymbachus koreanus Chûjô & Lee, 1993 is transferred to Sinocymbachus as S. koreanus (Chûjô & Lee) comb. nov.Sinocymbachus bimaculatus (Pic, 1927) is reported for the first time from China. The male of S. parvimaculatus (Mader, 1938) is discovered and described for the first time. Illustration, diagnosis and distribution are provided for each species. Prior to the present study, Sinocymbachus included ten species. An updated key to the species of Sinocymbachus is given.


Introduction
The genus Sinocymbachus is exclusively known in Southeast Asia and was established by Strohecker and Chûjô (1970) with Engonius excisipes Strohecker, 1943 from China (Sichuan) as the type species. It is a member of the largest endomychid subfamily Ly-the apical margin of the clypeus to the apex of the elytra; body width across both elytra at widest part; pronotal length from anterior angle to posterior margin; elytral length along the suture, including the scutellum. After observation, the dissected parts were mounted on the same card with the specimen. The abdomen was boiled in 10% NaOH solution, cleaned, and the aedeagus was dissected in distilled water. Habitus photographs were taken using a Canon EOS 5D III SLR camera and Canon MP-E 65 mm macro lens, and an Olympus OM-D E-M1 camera and Olympus ED 60 mm macro lens. Photographs of male genitalia and ae deagi were taken using a Canon EOS 5D III SLR camera and Canon MP-E 6 5mm macro lens. All photographs were refined in Adobe Photoshop CC 2015.

Sinocymbachus Strohecker & Chûjô
Sinocymbachus Strohecker & Chûjô, 1970: 511. Type species. Engonius excisipes Strohecker, 1943. Diagnosis. The species of Sinocymbachus appear to be closely related to Cymbachus. However, Sinocymbachus can be distinguished from Cymbachus in having the body more elongate in most cases (except S. parvimaculatus and S. sinicus sp. nov.); intercoxal process of mesoventrite distinctly longer than wide (except S. parvimaculatus and S. sinicus sp. nov.), and with median ridge or tubercle at base; mesotibiae sexually dimorphic, toothed and excised on inner edge in male, straight in female (modified based on Tomaszewska 2005).
Remarks. There is distinct sexual dimorphism in the species of the genus Sinocymbachus. The species of the genus Sinocymbachus bear distinct characters of sexual dimorphism. The mesotibiae of males usually have variously developed teeth and excisions. Besides, median lobe of the aedeagus is usually less complicated apically in the species with teeth and excisions symmetric on mesotibiae while it is more complicated in the species with teeth and excisions placed asymmetrically on tibiae and usually have a wide concavity on the ventral side of antenna. However, there are also exceptions. For example, the median lobe is complicated in the males of S. excisipes with symmetric teeth and excisions on mesotibiae while there is a wide concavity on the ventral surface of antenna in the males of S. humerosus with symmetrically placed teeth and excisions on mesotibiae. Etymology. The name refers to the type locality. Diagnosis. Sinocymbachus fanjingshanensis sp. nov. is most similar to S. angustefasciatus, S. longipennis sp. nov., S. quadriundulatus and S. wangyinjiei sp. nov. in appearance. However, S. fanjingshanensis sp. nov. differs from S. angustefasciatus by the shiny body (vs. body opaque); left mesotibia in male widely excised (vs. not excised); from S. longipennis sp. nov. by the body dark brown, shiny (vs. black, opaque); elytra oval with sides curved (vs. long oval, weakly curved); right mesotibia in male not excised (vs. with shallow and weakly undulate excision); from S. quadriundulatus by the body without cupreous sheen (vs. with cupreous sheen); left mesotibia in male widely excised (vs. not excised); from S. wangyinjiei sp. nov. by the mesoventral process with anterior and posterior margins nearly equally wide (vs. anterior margin much wider than posterior); mesotibia in male with shallow but broad excision (vs. with deep and narrow excision).
Distribution. China: Guizhou.  Etymology. The name refers to the distinctly elongate elytra, especially in male. Diagnosis. Sinocymbachus longipennis sp. nov. is most similar to S. angustefasciatus, S. fanjingshanensis sp. nov., S. quadriundulatus and S. wangyinjiei sp. nov. in external appearance. However, the distinctly more elongate elytra (especially in males) with nearly parallel sides can separate it from all these similar species. In addition, S. longipennis sp. nov. differs from S. angustefasciatus by having the elytra widest in the middle length (vs. behind middle); left mesotibia in male widely excised (vs. not widely excised); from S. fanjingshanensis sp. nov. by the body black and opaque (vs. dark brown, shiny); right mesotibia in male with shallow and weakly undulate excision (vs. not excised); from S. quadriundulatus by the body without cupreous sheen (vs. with cupreous sheen); left mesotibia in male widely excised (vs. not widely excised); from S. wangyinjiei sp. nov. by the body black and opaque (vs. dark brown, shiny); mesotibia in male with shallow and nearly straight excision (vs. with deeply U-shaped excision).

Sinocymbachus longipennis
Description. Length 9.5-10.6 mm. Body long and oval, 1.8 times as long as wide; convex; shiny. Colour black with four orange irregular maculae on elytra, narrow and transverse.
Abdomen. Ventrite 1 almost as long as subsequent two ventrites combined; ventrites 2-4 subequal in length. Ventrite 5 with lateral margin gradually converging posteriorly; posterior margin broadly rounded in male ( Etymology. The name is dedicated to our country which has created good research environment for us.
Diagnosis. Sinocymbachus sinicus can be separated from all its congeners by having the body short oval and each elytron with two transverse maculae, more regular without distinct projections.
Description. Length 8.9-9.1 mm. Body short oval, approximately 1.3 times as long as wide; moderately convex; smooth. Colour black with four orange irregular transverse maculae on elytra.
Thorax. Pronotum 2.3-2.4 mm long, 3.5-3.9 mm wide; widest near 1/2 of pronotal length; coarsely and rather densely punctate; lateral and anterior margins narrowly bordered; anterior edge with moderately large stridulatory membrane; sides nearly parallel; anterior angles produced, bluntly rounded; posterior angles moderately acute ly produced; disc weakly convex; two round raised areas laterally; inflexed laterally; median furrow absent; lateral sulci very short and deep, in form of triangular dent; basal sulcus weakly curved, moderately deep. Prosternal process (Fig. 3C) comparatively widely separating pro coxae; sides curved outwardly near apex, forked apically, not extending beyond front coxae. Mesoventral process (Fig.  3C) nearly pentagonal, as long as wide, with short median ridge anteriorly. Elytra 6.6-6.8 mm long, 5.0-5.2 mm wide; 2.8-2.9 times as long as pronotum; 1.3-1.4 times as wide as pronotum; punctures as large as the pronotal ones, densely distributed; sides strongly curved, widest near 1/2 length of elytron; humeri weakly prominent. Each elytron with two irregular transverse maculae. Anterior elytral macula located behind humerus, in form of arcuate irregular band; anterior margin deeply emarginate; posterior margin weakly emarginate or nearly straight; outer margin not touching lateral margin of elytra, inner margin distant from elytral suture. Posterior macula located at apical 1/3, in form of nearly straight band; outer and inner margin of macula distant from both elytral lateral margin and suture. Both mesotibiae (Fig. 4C) in male with small sharp tooth near apical 1/4 on inner edge, in female without teeth. Pro-and metatibiae simple. Etymology. The name is dedicated to Mr. Yin-Jie Wang, who collected the holotype of this species for our study.
Diagnosis. Sinocymbachus wangyinjiei sp. nov. resembles S. angustefasciatus, S. fanjingshanensis sp. nov., S. longipennis sp. nov., and S. quadriundulatus. However, it can be differentiated from S. angustefasciatus by the body shiny (vs. opaque); mesotibia in male with deeply U-shaped excision (vs. not excised); from S. fanjingshanensis sp. nov. by the anterior margin of mesoventral process much wider than posterior margin (vs. anterior margin as wide as posterior margin); mesotibia in male with deep and narrow excision (vs. with shallow and wide excision); from S. longipennis sp. nov. by the body dark brown and shiny (vs. black, opaque); elytra oval with sides distinctly curved (vs. long oval, nearly parallel); mesotibia in male with deep and narrow excision (vs. with shallow and wide excision); from S. quadriundulatus by the body without cupreous sheen (vs. with cupreous sheen); mesotibia in male with deeply U-shaped excision (vs. not excised).
Description. Length 9.7 mm. Body oval, approximately 2.1 times as long as wide; convex; shiny. Colour black, shiny, with four orange irregular transverse maculae on elytra.
Thorax. Pronotum 2.1 mm long, 3.2 mm wide; widest at base; rather coarsely and densely punctate; lateral and anterior margins narrowly bordered; anterior edge with large stridulatory membrane; sides undulate, deeply emarginate near basal 1/4 length; anterior angles bluntly produced; posterior angles acute ly produced; disc weakly convex; median furrow absent; lateral sulci short and deep, in form of triangular dent; basal sulcus sinuate, moderately deep. Prosternal process (Fig. 3D) moderately widely separating pro coxae; sides curved outwardly toward apex, forked apically, not extending beyond front coxae. Mesoventral process (Fig. 3D) nearly pentagonal, distinctly longer than wide; sides converging to apex; disc with short median ridge anteriorly. Elytra 7.2 mm long, 4.6 mm wide; 3.4 times as long as pronotum; 1.4 times as wide as pronotum; punctation coarse and dense; sides curved, widest near 1/2 length of elytron; converging from here to apex; humeri weakly prominent. Each elytron with two irregular transverse maculae: anterior elytral macula located on humerus, nearly W-shaped; outer margin touching lateral margin of elytra, inner margin distant from elytral suture; posterior macula located at apical 1/3, transverse bands with four distinct projections; outer margin distant from lateral margin of elytra, inner margin distant from elytral suture. Left mesotibia (Fig. 4D-1) in male with small sharp tooth behind 1/2 length on inner edge, then deeply U-shaped excised; right mesotibia ( Fig.  4D-2) in male with small sharp tooth near apical 1/3 on inner edge, then deeply Ushaped excised. Pro-and metatibiae simple.
Distribution. China: Hubei. Figures 12A, 13A  Diagnosis. Sinocymbachus bimaculatus is most similar to S. humerosus in appearance, sharing two round maculae on each elytron. However, S. bimaculatus differs from S. humerosus by the scutellum (Fig. 7) being distinctly longer than wide (vs. nearly as long Biology and ecology. The adults were collected by shaking the tree from a large clump of dead wood of Fagaceae plants (Mt. Limushan, Qiongzhong, Hainan) (Fig.  8A, B). The adults and larvae were hand collected from a large pile of dead bamboos (Yangmeiao, Huanjiang, Guangxi) (Fig. 8D, E). The adults and larvae apparently feed together (Fig. 8C). Sinocymbachus bimaculatus is not only most similar to S. humerosus, but both are also sympatric. Figures 12C, 13C, 14C, 15C, 16C, 17C, 18C

Sinocymbachus luteomaculatus
Engonius luteomaculatus Pic, 1921: 1. Cymbachus luteomaculatus: Strohecker 1953: 91. Sinocymbachus luteomaculatus: Strohecker and Chûjô 1970 Diagnosis. Based on Strohecker & Chûjô (1970), Sinocymbachus luteomaculatus can be separated from all its congeners by having the basal and apical elytral maculae briefly undulately fasciate, but in one specimen examined by the author base of elytron is composed of two spots (Fig. 18F), this elytral pattern is most similar to S. decorus and S. politus by sharing two basal spots and one narrow transverse apical macula on each elytron. However, S. luteomaculatus differs from S. decorus by having an opaque body (vs. shiny) and humeri weakly prominent (vs. distinctly prominent); from S. politus by the elytra distinctly more elongate (vs. not elongate); two basal elytral maculae arranged in an oblique line (vs. arranged in a horizontal line); mesotibial tooth in male asymmetric (vs. symmetric).

Sinocymbachus parvimaculatus
Length. 7.7 mm-8.5 mm; width: 5.6 mm. Description of male. Length 7.8 mm. Body short oval, approximately 1.5 times as long as wide; strongly convex; smooth. Colour black with four orange round spots on elytra.
Thorax. Pronotum 1.5 mm long, 3.5 mm wide; widest at base; moderately coarsely and rather densely punctate; lateral and anterior margins narrowly bordered; anterior edge with moderately large stridulatory membrane; sides weakly undulate; anterior angles produced, bluntly rounded; posterior angles moderately acute ly produced; disc weakly convex; median furrow absent; lateral sulci very short and deep, in form of triangular dent; basal sulcus curved, moderately deep. Prosternal process moderately widely separating pro coxae; sides curved outwardly near apex, forked apically, not extending beyond front coxae. Mesoventral process nearly pentagonal, as long as wide, with short median ridge near basal 1/4. Elytra 5.9 mm long, 5.3 mm wide; 3.9 times as long as pronotum; 1.5 times as wide as pronotum; punctures as large as the pronotal ones, more dense; sides strongly curved, widest near 1/2 length of elytron; humeri weakly prominent. Each elytron with two round maculae: anterior macula located near basal 1/5, posterior macula located at apical 1/3, and all these maculae placed in mid-line of elytron; outer and inner margins of macula very distant from elytral lateral margin and suture. Mesotibia with small sharp tooth near apical 1/4 on inner edge, then with deep, small, U-shaped excision. Pro-and metatibiae simple.