Two new species of the genus Dryopomorphus Hinton, 1936 from China (Coleoptera, Elmidae)

Abstract Two new species of the genus Dryopomorphus Hinton, 1936 are described from China: Dryopomorphus heineri sp. n. and D. ruiliensis sp. n. Habitus photographs and detailed line drawings of the male genitalia are provided.


Introduction
The genus Dryopomorphus Hinton, 1936 occurs in eastern Asia, from China and Japan to Malaysia and Brunei. Fourteen species of this genus were described until now (Hinton 1971, Spangler 1985, Kodada 1993, Yoshitomi and Satô 2005, Čiampor and Kodada 2006, Čiampor et al. 2012, Yoshitomi and Jeng 2013, Jäch et al. 2016). Yoshitomi and Satô (2005) reviewed the four species of Japan. Čiampor et al. (2012) reviewed the Dryopomorphus species of Malaysia, from where three known species were diagnosed and five new species were described.
The presence of the genus Dryopomorphus in China was indicated by Jäch and Kodada (1995) based on specimens collected during the China Water Beetle Survey (CWBS), but the authors did not give detailed species information. In the catalogue of Elmidae (Jäch et al. 2016), there is no record of this genus from China, so this is the first time that the genus Dryopomorphus is reported from China formally. In this article, two new species of this genus, collected during the China Water Beetle Survey, are described.

Materials and methods
Specimens were examined with a Leica M205c stereomicroscope and an Olympus BX51 compound microscope. Genitalia were drawn with the aid of a drawing tube. Male genitalia were placed in concentrated lactic acid in a cavity slide for at least several hours before they were examined. Habitus photographs were made with a KEYENCE VHX-2000 -Super Resolution Digital Microscope System. Label data are cited verbatim, with separate lines on the same label indicated by a slash "/"; different labels are separated by a vertical line"|".
Abbreviations used in the text: BL body length = PL+EL, BW maximum width of body, PL pronotal length, PW maximum width of pronotum. Diagnosis. Body elongate suboval, distinctly convex, large (BL: 3.64-3.81 mm), head and pronotum dark brown, elytra brown; anterior angles of pronotum explanate, distinctly protruding, median sulcus of pronotum clearly impressed from basal 0.1 to 0.6, sublateral sulci present in basal 0.4; elytral intervals 3, 5, 7 slightly elevated in basal third. This species is similar to D. siamensis Kodada, 1993 by parameres being angulate at apex, but it can be distinguished by its smaller and slimmer penis, which is distinctly shorter than the parameres.
Head. Labrum short, partly concealed by clypeus, anterior margin truncate with dense yellowish long setae laterally. Clypeus approx. twice as wide as long, slightly emarginated anteriorly, densely punctate and pubescent. Frontoclypeal suture straight, distinct, but not deeply impressed. Vertex densely punctate, setose, with dark triangular area. Eyes large, slightly protruding from head outline, sub-triangular in lateral view.
Elytra. EL 2.71 mm, EW 1.71 mm, distinctly convex, basal 1/2 subparallel, then converging to separately rounded apices, densely punctate and pubescent. Each elytron with 10 striae, punctures in discal part of striae medium-sized and in lateral part of striae larger and distinct; intervals 3, 5 and 7 slightly elevated in basal third, with dense micro-punctures. Scutellum longer than wide, sides arcuate.
Aedeagus (figures 5-7). Approximately 1 mm long. In ventral view, phallobase wide, slightly shorter than penis, distinctly shorter than parameres. Distal half of penis distinctly narrowed, apices narrowly rounded; ventral sac folded, but distinctly expanding if placed in lactic acid for more than two days. Parameres distinctly longer than penis, gradually narrowed from base towards angulate apex.

Distribution. China (Guangdong).
Etymology. This species is dedicated to our deceased friend Heinrich (Heiner) Schönmann, Vienna, a specialist in Hydrophilidae and good collector. Diagnosis. Body elongate, dark brown; anterior angles of pronotum explanate, slightly protruding, median sulcus of pronotum straight, present at posterior 0.7 and sublateral sulci present in posterior 0.3; elytral punctures on disc small and in lateral striae large and distinct. This species can be distinguished from Dryopomorphus heineri sp. n. by: 1. pronotum less convex, anterior angles less protruding; 2. elytra subparallel in basal 2/3, then gradually converging posteriorly to separately rounded apices; 3. parameres slightly extending beyond penis, with apices narrowly rounded, whereas in D. heineri sp. n. the parameres distinctly extend beyond penis and the apices are angulate. This species can be distinguished from all other known species of the genus by the different shape of the parameres which are gradually narrowed from the base towards the apex in ventral view, distinctly narrowed in basal half in dorsal view, with sub-distal portion slightly inflated and apices narrowly rounded.
Description (holotype). Body elongate, BL 4.14 mm, BW 1.88 mm, dorsal surface covered with short adpressed yellowish setae and long sub-erect setae which are black on the basal 3/4 and yellowish at the distal 1/4. Dorsum dark brown, anterior corners of pronotum and legs reddish brown, antennae yellowish brown, ventral surface dark brown.
Head. Partly retractable into thorax. Labrum short, densely setose, anterior margin almost truncate, with long yellowish setae, lateral angles almost rounded. Clypeus longer and wider than labrum, approx. twice as wide as long, densely setose, frontoclypeal suture straight; surface of labrum and clypeus densely punctate. Eyes large, slightly protruding from head outline. Pubescence of frons denser on a central triangular area; frons and vertex densely punctate, punctures setose. Thorax. Pronotum widest at base, broader than long. PL 0.96 mm, PW 1.49 mm. Disc convex, densely punctate, lateral margin narrowly rimmed, slightly tilt inward, anterior angles slightly protruding. Median sulcus straight, present along posterior 0.7 of pronotum; sublateral sulci deeply impressed, present on posterior 0.3 of pronotum. Hypomeron sub-parallel, narrowed posteriorly, anterior depression developed for reception of antennae; surface coarsely punctate, densely setose. Prosternal process 1.8 times as long as prosternum in front of coxae, lateral margin distinctly raised and sub-parallel at anterior 0.7, posterior margin distinctly produced medially; surface of prosternum densely setose and sublateral area very coarse. Mesoventrite short, mesoventral cavity for reception of prosternal process very deep. Metaventrite impressed anteriorly between mesocoxae; discrimen narrow, present from anterior impression to posterior margin; disc flat, finely and densely punctate, densely setose; sub-lateral area with two kinds of punctures, fine punctures dense, large punctures sparse.