Description of two new species of Dineutus sensu stricto from Southeast Asia (Coleoptera: Gyrinidae) with a key to the known species of the subgenus Author Gustafson, Grey T. Department of Biology and Museum of Southwestern Biology, University of New Mexico, Albuquerque, NM 87131, USA; e-mail: gtgustafson @ gmail. com Author Hájek, Jiří Department of Entomology, National Museum, Cirkusová 1740, CZ- 193 00 Praha 9 - Horní Počernice, Czech Republic; e-mail: jiri _ hajek @ nm. cz Author Miller, Kelly B. Department of Biology and Museum of Southwestern Biology, University of New Mexico, Albuquerque, NM 87131, USA; e-mail: gtgustafson @ gmail. com & e-mail: kbmiller @ unm. edu text Acta Entomologica Musei Nationalis Pragae 2016 2016-11-15 56 2 629 643 journal article 10.5281/zenodo.5310734 0374-1036 5310734 1F05D2DD-2995-4D19-B242-72E6C91F7E43 Dineutus sitesi sp. nov. (Figs 6, 14, 21, 22, 25) Type material. HOLOTYPE : J (pinned, with aedeagus in microvial), ‘THAILAND: Phitsanulok Prov. / Phu Hin Rongkla Natl. Park. / 16º59’N 101º00’E 1280m / 15Nov.2002 . CMU Team / Waterwheel Falls’ [white label, typed, black ink] // ‘ HOLOTYPE / Dineutus sitesi sp. nov. / Gustafson , Hájek & Miller , 2015’ [red label, typed, black ink] (deposited at the MSBA ) . PARATYPES ( 15 specimens ): THAILAND : PHITSANULOK : same label data as holotype ( 5 spec. UMCE ) ; same as previous except: ‘ 6.v.2003 . colls: Vitheepradit , / Prommi , Ferro. Water surface. / L-285’ [white label, typed, black ink] ( 2 spec. USNM ) ; same as previous except: ‘ 21April2002 . / Kick pool. coll. N.Changthong’ [white label, typed, black ink] ( 1 spec. NSMT ) ; same as previous except ‘ 10.III.2002 . colls: Sites,AV , / Kirawanich’ [white label, typed, black ink] ( 1 spec. UMCE ) ; ‘ THAILAND: Phitsanulok Prov. / Phu Hin Rongkla Natl. Park. / Namtok Huai Khamuen Noi. / Pool 16º59‘N 101º60‘E 1220m / 22May2002 . CMU Team’ [white label, typed, black ink] ( 1 spec. UMCE ) ; same as previous except: ‘ 15July2002 ’ [white label, typed, black ink] ( 2 spec. USNM , 1 spec. MSBA , 1 spec. NMPC ) ; same as previous except ‘ 10April2003 ’ ( 1 spec. NSMT ). All paratypes provided with additional label ‘ PARATYPE / Dineutus sitesi sp. nov. / Gustafson, Hájek & Miller, 2015’ [red label, typed, black ink]. Diagnosis. Body form (Fig. 6) evenly elongate oval, males laterally slightly expanded just posterior to midlength, in lateral view dorsoventrally evenly convex; antenna with six antennomeres; elytral apices without significant apicolateral sinuation present (Fig. 14), apex broadly rounded, preapical sericeous patch of reticulation absent, lateral marginal depression relatively broad; male protarsus ( Fig. 22 ) relatively broad. Aedeagus ( Fig. 21 ): median lobe parallel sided for 3/4 its length, narrowed in apical fourth with straight lateral margins, apex triangular, tip with distinct constriction, in lateral view apex strongly dorsally curved. Female reproductive tract ( Fig. 25 ): spermatheca relatively short and broad, gonocoxae slightly laterally expanded, apex broadly rounded. Description of male holotype . Habitus. Larger member of genus; body form elongate oval, attenuated anteriorly, widest point just posterior to midlength of elytra; in lateral view greatest convexity just posterior to scutellar region, evenly convex relative to other Dineutus s. str. species. Coloration. Head dorsally, pronotum, and elytra bronzy-olive-green, elytra and pronotum uniformly bronzed in appearance, elytra without sericeous patch preapically, venter reddish brown with elytral epipleuron, middle- and posterior legs, and abdomen lighter. Head. Dorsally, vertex with reticulation composed of round to ovoid scultpicells; frons with reticulation composed of ovoid sculpticells, punctation sparse and shallow, almost imperceptible, mostly effaced by uniform reticulation, some shallow wrinkles present medially, apicolateral corners of frons wrinkled, frontoclypeal suture with posterior margin straight, lateral margins obtusely angled, almost arcuate; clypeus shallowly emarginate anteriorly, appearing truncate in dorsal view, with faint wrinkles laterally, strong reticulation composed of round sculpticells, effaced at extreme anterior margins, punctation sparse, punctures appear shallow in reticulation but more impressed at anterior margin where reticulation imperceptible; labrum with regular punctation marginally, extending posteriad to basomedial half, punctures well impressed, reticulation present basomedially, composed of elongate ovoid sculpticells, faintly impressed; labial palps with ultimate palpomere with asymmetrical anterior and posterior margins, anterior margin weakly curved, nearly straight, posterior margin evenly curved towards apex, apex broadly rounded. Figs 24–25. Female reproductive tract of new Dineutus s. str. species. 24 – D. barong sp. nov. ; 25 – D. sitesi sp. nov. Scale bars = 1 mm. Thorax. Pronotum with medial narrow darkly pigmented strip on disc, running nearly length of pronotum, strong regular reticulation over entirety of pronotum composed of round sculpticells, these slightly larger and more regularly rounded laterally, punctation regular, punctures shallowly impressed, nearly imperceptible except upon close examination; pronotal transverse impressed line well impressed and nearly complete, medially weakened and irregular, but still traceable, lateral marginal depression of pronotum narrow with shallow and short wrinkles present, especially in anterolateral corners, posterior margin of pronotum fairly strongly sinuate. Profemora with two sub-apicoventral teeth, one on anteroventral margin, one on posteroventral margin, teeth relatively small and similar in size; protibial distolateral margin broadly rounded, indistinct; protarsus relatively broad, with lateral margins flatly rounded, ultimate protarsomere slightly less than 2× longer than wide; mesotarsal claws with anterior claw narrow, sharply curved, with ventral margin nearly straight, weakly narrowing in apical third. Elytra completely cover scutellar shield, lateral marginal depression weakly evident, narrow in basal third, interrupted by swelling created by ventral depression where forelegs are received, then broadened to nearly twice width in apical 2/3; sericeous preapical patch of reticulation completely absent; reticulation dense and regular throughout, composed of round sculpticells; all elytral striae faintly evident, apicolateral sinuation feebly present. Figs 26–27. Habitat of D. barong sp. nov. 26 – Jan Šumpich in general habitat; 27 – D. barong sp. nov. in habitat, individuals demarcated by circles. Genitalia. Aedeagus ( Fig. 21 ) with median lobe just shorter than parameres, parallel sided for 3/4 its length, narrowed in apical fourth with straight lateral margins, apex triangular, with tip constricted; in lateral view tip of median lobe strongly dorsally curved; dorsally apical half with setigerous punctures; parameres laterally expanded in apical third, apex flatly rounded. Variability. Apicolateral sinuation of elytra almost appearing absent in some individuals. Sexual dimorphism . Male broader and more attenuated anteriorly, female much more regularly oval in body form. Female reproductive tract with lateral margins of gonocoxae weakly expanded, apex broadly rounded, laterotergites apically weakly laterally expanded, spermatheca smaller and rounder, not strongly elongate and curved to left after fertilization duct. Measurements . Male: length = 15.0–17.0 mm ( holotype = 17.0 mm), width = 10.0–11.0 mm ( holotype = 10.5 mm ). Female: length = 14.0–16.0 mm width = 9.0–10.0 mm. Differential diagnosis. Dineutus sitesi sp. nov. is most similar to D. fulgidus in having the elytra with weak apicolateral sinuation (cf. Figs 13–14), absence of a preapical sericeous reticulation patch, and more brownish olive green coloration. However, it can be distinguished from that species by the much more regularly elongate oval body form (much more narrow in habitus) (cf. Figs 6–7), the broader protarsi ( Fig. 22 ), and the form of the aedeagus (cf. Figs 15 and 21 ) and female reproductive tract. The aedeagus differs in having a more narrowly rounded tip and less acuminate apex of median lobe ( Fig. 21 ), the female reproductive tract differs in having narrow gonocoxae that are less laterally expanded. Etymology. This new species is named in honour of the aquatic hemipterist Robert Sites, leader of the CMU Team who collected most of the specimens of this new species and who, in collaboration with Akekawat Vitheepradit, is working on a project to make the aquatic insects of Thailand known. The name is a noun in the genitive case. Distribution. This species is currently only known from Phu Hin Rongkla National Park, Phitsanulok Province , Thailand ; an area that appears to exhibit high levels of endemism for aquatic insects ( SITES & POLHEMUS 2001 , VITHEEPRADIT & SITES 2007 ). It may be that this new species is only found within this region.