The Gyrinidae (Coleoptera) fauna of Thailand: Key to tribes and genera, with new records and keys to species of Dineutini and Gyrinini Author Suksai, Benjamart 0000-0002-2472-6100 benjamartbenjamart@gmail.com Author Gustafson, Grey T. Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas 66045, USA. & Department of Biological Sciences, Northern Arizona University, Flagstaff, Arizona, 86011, USA. Author Sites, Robert W. 0000-0002-3895-813X Enns Entomology Museum, Division of Plant Science, University of Missouri-Columbia, Missouri 65211, USA. SitesR @ missouri. edu; https: // orcid. org / 0000 - 0002 - 3895 - 813 X Author Sangpradub, Narumon Applied Taxonomic Research Center, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand text Zootaxa 2021 2021-11-22 5071 1 97 117 journal article 3307 10.11646/zootaxa.5071.1.5 f5a054cf-41c7-40cd-bac9-63e1ea8d1b8e 1175-5326 5723327 C7DFE939-E932-4570-8496-7A67A51D4D7A Dineutus sitesi Gustafson, Hájek & Miller, 2016 ( Figs. 1E, 1I , 4B , 5F–I , 7D , 8A ) Material examined. THAILAND : Kanchanaburi Province : Thong Pha Phum Natl. Park, Huay Ka Yeang Stream , Hin Dat Subdistrict , Thong Pha Phum District , 14°33'18.0''N 98°35'51.8''E , 270 m a.s.l. , 25.II.2002 , leg. S. Saeheag , 1 male ( NHMW ) . Phitsanulok Province : Phu Hin Rongkla Natl. Park, Huai Khamin Noi Waterfall , Pool , 16°59'N 101°00'E , 1220 m a.s.l. , 10.III.2002 , leg. R. Sites , A. Vitheepradit & K. Kirawanich , 1 female ( UMC ) ; same locality except for, 22.V.2002 , leg. CMU Team , 1 female ( UMC ) ; same locality except for, Waterwheel Falls , 16°59'N 101°00'E , 1280 m a.s.l. , 12.VII.2003 , leg. N. Changthong , 1 female ( THNHM ) ; same locality except for, 15.XI.2002 , leg. CMU Team , 3 males ( UMC , THNHM ) , 2 females ( UMC ) ; same locality except for, 5.V.2003 , leg. N. Changthong , 1 male ( UMC ) ; Thung Salaeng Luang Natl. Park , Tum Din Stream , Ban Mung Subdistrict , Noen Maprang District , 16°29'07.5"N 100°48'31.2"E , 894 m a.s.l. , 23.III.2011 , leg. N. Sangpradub , 2 females ( KKU ) . FIGURE 5. Elytral apex, aedeagus and gonocoxae of species of Dineutus : (A–E) D. australis : (A–B) elytral apex, scale bar = 2 mm: (A) male; (B) female; (C–D) aedeagus, scale bar = 0.5 mm: (C) dorsal view; (D) lateral view; (E) gonocoxae, ventral view, scale bar = 0.5 mm; (F–I) D. sitesi : (F) male elytral apex, scale bar = 2 mm; (G–H) aedeagus, scale bar = 1 mm: (G) dorsal view; (H) lateral view; (I) gonocoxae, ventral view, scale bar = 1 mm; (J–M) D. spinosus : (J) male elytral apex, scale bar = 2 mm, (K–L) aedeagus, scale bar = 0.5 mm: (K) dorsal view; (L) lateral view; (M) gonocoxae, ventral view, scale bar = 0.5 mm. Diagnosis. Male ( Fig. 1E ): Size: 15.0–17.0 mm. Body form broadly oval; apex of flagellomere VI darkly colored, black; elytral apices without parasutural spines, epipleural spines and serrations absent ( Fig. 5F ), elytral apex rounded ( Fig. 1E ); lateral margin of pronotum and elytron darkly colored, black; protrochanter apically without setae on ventral surface ( Fig. 4B ); profemur with sub-apicoventral tooth; protibia club-shaped; venter reddish to brown ( Fig. 1I ); epipleura reddish to black ( Fig. 1I ); aedeagus ( Figs. 5G–H ) with median lobe shorter than parameres, parallel-sided for 3/4 length, narrowed in apical 1/5, apex triangular, curved dorsally in lateral view. Female: Similar to male except for size: 13.4–15.7 mm ; apex of flagellomere VI lightly colored, orange; profemur without sub-apicoventral tooth; gonocoxae elongate, lateral margins slightly rounded and expanded, apex rounded ( Fig. 5I ). Differential diagnosis. Dineutus sitesi can be distinguished from all other congeners in Thailand by the broadly oval body form, large size, rounded elytral apex lacking spines and serrations, and males with a sub-apicoventral profemoral tooth. Distribution. This species is known only from Thailand where it was described from Phu Hin Rongkla National Park, Phitsanulok Province (Gustafson et al . 2016). Habitat. This species occurs in streams and pools beneath waterfalls ( Fig. 7D ) (Gustafson et al . 2016). Discussion. In this study, D. sitesi was found at the same localities in Phu Hin Rongkla National Park as previously reported by Gustafson et al. (2016). Additionally, we found this species in another stream within the same mountain range ( Phetchabun Mountains) at Thung Salaeng Luang National Park, Phitsanulok Province at an elevation of 894 m a.s.l. D. sitesi was also collected from a stream in the Tenasserim Hills at Thong Pha Phum National Park, Kanchanaburi Province at an elevation of 270 m a.s.l. ( Fig. 8A ). Thus, more collecting in the northern and western regions where the mountain ranges approach continuity will be required further in order to better understand its distribution.