A key to species of the genus Gastroserica Brenske of the China (Coleoptera, Scarabaeidae, Sericini), with the description of two new species and two new records for China

Abstract Based on a revision of the material housed in Chinese collections and a key to species of Gastroserica of China is provided. Two new species are described, habitus photographs, and illustrations of the genitalia are given: Gastroserica nigrofasciata sp. n. (from China: Guangxi and Guizhou Prov.), Gastroserica yunnanensis sp. n. (from China: Yunnan Prov.). Besides, illustrations of the genitalia of species mentioned in the key are provided. Additional distribution records of the Gastroserica species including an updated distribution map are given.


1
Labroclypeus widest at middle, lateral margins more or less distinctly narrowed towards base, or subparallel. Pronotum with or without longitudinal median impressions .. Eyes strongly protruding, labroclypeus very narrow (ratio maximal width of head including eyes/ width of labroclypeus: 1.8-1.9 Even intervals of elytra black, but behind the middle, all the intervals black, with two brown spots at the apex of elytra. Interior apical angle of elytra with a strong seta ( Description. Length: 6.0-7.0 mm, length of elytra: 4.5-5 mm, width: 3.5-4.0 mm. Body oval, elytra brown, dorsal surface pale yellow to pale brown, densely covered with short, fine, adpressed setae and with moderately dense, long, erect setae interspersed, abdominal sternites dark brown to black. (Fig. 1 G) Labroclypeus subrectangular and short, widest before apex, lateral margins straight, nearly parallel to each other and weakly convergent toward base, anterior angles broadly rounded, lateral border and ocular canthus produced into a distinct obtuse angle, anterior margin weakly reflexed, straight, surface weakly convex medially and moderately shiny, very coarsely and sparsely punctate, with several long, erect setae; frontoclypeal suture distinctly impressed and moderately curved, smooth area    Ahrens and Pacholátko 2003) in front of eye slightly wider than long (1.5/1); ocular canthus moderately short and slender, finely and densely punctate. Frons completely black or only the part near the posterior portion brown, other parts of frons black, with coarse, dense punctures, with fine punctures irregularly interspersed, densely erectly setose. Eyes moderately large, ratio of diameter/ interocular width: 0.6. Antenna yellow, club yellow to brown, with ten antennomeres club with four antennomeres equal in length, the length of club a little longer than the remaining antennomeres combined. Mentum strongly elevated and flattened anteriorly. Pronotum subrectangular, widest at anterior third, lateral margins strongly convergent anteriorly, before posterior angles weakly sinuate, anterior angles not produced and strongly rounded, almost obsolete, posterior angles moderately blunt and moderately produced outward, anterior margin almost straight, with a distinct and fine marginal line, basal margin moderately curved without marginal line, but two weak impressions at a quarter to the lateral margins; surface with moderately dense and fine punctures, with numerous minute setae, which are bent backwards, with a longitudinal, straight, brown line in the middle and two black spots at sides of the disc; anterior and lateral borders setaceous; basal margin of hypomeron strongly produced ventrally, before base distinctly transversely sulcate. Scutellum nearly triangular, apex weakly rounded, with fine and dense punctures, medially smooth and weakly elevated, minute setae present in the punctures.
Elytra oblong, widest at middle, striae distinctly impressed and finely densely punctate, intervals weakly convex, with fine and sparse punctures that are almost concentrated along the striae, minutely setose in the punctures, odd intervals with single coarse punctures bearing each a strong erect seta, near the anterior margin, even intervals black, but behind the middle, all intervals black, with two brown spots at the apex of elytra; epipleural edge moderately strong, ending at the strongly convex external apical angle of elytra, epipleura densely setaceous, apical border chitinous, without short microtrichomes.
Ventral surface dull, with large and dense punctures, with dense, short setae, setae adpressed, metacoxa partly glabrous, laterally with fine adpressed setae, each abdominal sternite with an indistinct transversal row of coarse punctures bearing a short, strong seta between fine and dense punctation, all sternites with fine, short setae. Mesosternum between mesocoxae almost as wide as mesofemur, with numerous strong setae. Ratio of length of metepisternum/ metacoxa: 1/ 1.82. Pygidium long, apically produced and strongly convex, with fine and dense punctures bearing fine setae and a few robust punctures bearing robust setae, without smooth midline.
Legs pale yellow to brown, moderately slender and shiny; femora finely densely punctate and setose, with two longitudinal rows of setae; anterior edge of metafemur acute, lacking an adjacent serrated line, posterior margin weakly convex, with a few fine setae medially, ventrally weakly widened in apical half but not serrate, dorsally serrate, with short setae. Metatibia moderately broad, at middle convexly widened, ratio width/ length: 1/3.4, dorsally sharply carinate, with two groups of spines, the basal group at one third, apical one at two third of metatibia length, basally with a few single spines in punctures; lateral face longitudinally convex, with dense and moderately coarse punctures, some of them longitudinally impressed, ventral edge serrated, medial face not punctate and smooth, apex interiorly near tarsal articulation sharply truncate. Tarsomeres dorsally glabrous and finely punctate, ventrally with sparse, short setae, metatarsomeres dorsally with strong longitudinal impressions, ventrally with a strongly serrated ridge, laterally with a strong longitudinal carina, first metatarsomere as long as the following two tarsomeres combined and twice as long as the upper tibia spur. Protibia short, bidentate, protarsal claws symmetrical. Fig. 1 A-C. Variation. Smooth area in front of eye wider than long (the rate from 1.5/1 to 1.7/1). Ratio of eye diameter / interocular width: (0.60-0.62). There are no brown spots at the end of elytra in some specimens, and after the middle, the odd intervals are still brown. Ratio of length of metepisternum/ metacoxa: (0.43~0.55).

Aedeagus.
Diagnosis. Gastroserica yunnanensis sp. n. is very similar to G. bilyi Ahrens, 2000, in shape of male genitalia and habitus. It maybe differentiated from G. bilyi by two brown spots at the end of elytra and sharp apex of right paramere.

Gastroserica nigrofasciata
Labroclypeus subrectangular and short, widest at base, lateral margins straight and moderately divergent from anterior angles to base, anterior angles broadly rounded, lateral border and ocular canthus produced into a distinct obtuse angle, anterior margin weakly reflexed, straight, surface weakly convex medially and moderately shiny, very coarsely and sparsely punctate, with several long, erect setae; frontoclypeal suture distinctly impressed and strongly curved, smooth area in front of eye distinctly wider than long (1.8/1); ocular canthus moderately short and strong, finely and densely punctate. Frons with coarse, dense punctures, with fine punctures irregularly interspersed, densely erectly setose. Eyes moderately large, ratio of diameter/ interocular width: 0.63. Antenna brown, with ten antennomeres, club in male with four antennomeres, first joint of club slight shorter than the others, club slightly longer than the remaining antennomeres combined. Mentum elevated and flated anteriorly.
Pronotum rectangular, widest at half of length, lateral margins strongly convergent anteriorly, before posterior angles weakly sinuate, anterior angles not produced and strongly rounded, almost obsolete, posterior angles moderately blunt and weakly produced outward, anterior margin almost straight, with a distinct and fine marginal line, basal margin moderately curved without marginal line, and two weak impressions at quarter of width to the lateral margins; surface with moderately dense and fine punctures, with numerous minute setae, which are bent backwards and two black spots at the middle, along the middle weakly medially impressed, with a weakly elevated transverse carina behind the middle; anterior and lateral borders setaceous; basal margin of hypomeron strongly produced ventrally, before base distinctly transversely sulcate. Scutellum nearly triangular, apex weakly rounded, with fine and dense punctures, medially smooth, minute setae present in the punctures.
Elytra oblong, widest at middle, striae distinctly impressed and finely densely punctate, intervals weakly convex, with fine and sparse punctures that are almost concentrated along the striae, minutely setose in the punctures, odd intervals with single coarse punctures bearing each a strong erect seta, even intervals brown to black; epipleural edge moderately strong, ending at the strongly convex external apical angle of elytra, epipleura densely setaceous, apical border chitinous, without short microtrichomes.
Ventral surface dull, with large and dense punctures and dense short setae, setae adpressed, metacoxa partly glabrous, laterally with fine adpressed setae, each abdominal sternite with indistinct transversal row of coarse punctures bearing each a short strong seta between fine and dense punctation, all sternites with fine, short setae. Mesosternum between mesocoxae almost as wide as mesofemur, with numerous strong setae. Ratio of length of metepisternum/ metacoxa: 1/ 2.0. Pygidium long, apically produced and strongly convex, with fine and dense punctures bearing fine setae and a few robust punctures bearing each a robust seta, without smooth midline.
Legs pale yellow to yellow brown, moderately slender and shiny, femora finely densely punctate and setose, with two longitudinal rows of setae; anterior edge of metafemur acute, lacking an adjacent serrated line, posterior margin weakly convex, with a few fine setae medially, ventrally weakly widened in apical half but not serrate, dorsally serrate, with short setae. Metatibia moderately broad, at middle convexly widened, ratio width/ length: 1/ 3.2, dorsally sharply carinate, with two groups of spines, the basal group at one third, apical one at two third of metatibial length, basally with a few single spines in punctures; lateral face longitudinally convex, with dense and moderately coarse punctures, some of them longitudinally impressed, ventral edge serrated; medial face not punctate and smooth, apex interiorly near tarsal articulation sharply truncate. Tarsomeres dorsally glabrous and finely punctate, ventrally with sparse, short setae, metatarsomeres dorsally with strong longitudinal impressions, ventrally with a strongly serrated ridge, laterally with a strong longitudinal carina, first metatarsomere as long as the following two tarsomeres combined and twice as long as the upper tibia spur. Protibia short, bidentate, protarsal claws symmetrical.

Variation.
Smooth area in front of eye wider than long (the rate from 1.8/1 to 2.0/1). Eyes weakly large, ratio of diameter/ interocular width: (0.60-0.67). Club a little shorter than the remaining antennomeres combined in female. Elytra from yellow to brown, with greenish metallic shine. Three intervals next to the lateral margins of elytra sometimes black. Ratio of length of metepisternum/ metacoxa: (1/ 1.82-2.).
Diagnosis. Gastroserica nigrofasciata sp. n. is in habitus very similar to G. marginalis (Brenske, 1897). It maybe differentiated from G. marginalis by the colour of elytra and dorsal surface, the presence of two long lateral apophyses at the apex of phallobasis, and the shape of parameres.