The Gyrinidae (Coleoptera) fauna of Thailand: Key to tribes and genera, with new records and keys to species of Dineutini and Gyrinini Suksai, Benjamart Gustafson, Grey T. Sites, Robert W. Sangpradub, Narumon Zootaxa 2021 2021-11-22 5071 1 97 117 Gustafson, Hajek & Miller, 2016 Gustafson, Hajek & Miller 2016 [151,744,1789,1816] Insecta Gyrinidae Dineutus Animalia Coleoptera 7 104 Arthropoda species sitesi  ( 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 ma.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 ma.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 ma.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 ma.s.l.,  23.III.2011, leg. N. Sangpradub, 2 females( KKU).   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 sitesican be distinguished from all other congeners in Thailandby 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 Thailandwhere 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. sitesiwas 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 ( PhetchabunMountains) at Thung Salaeng Luang National Park, Phitsanulok Provinceat an elevation of 894 ma.s.l.  D. sitesiwas also collected from a stream in the Tenasserim Hills at Thong Pha Phum National Park, Kanchanaburi Provinceat an elevation of 270 ma.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. 3411799426 2002-02-25 NHMW S. Saeheag Thailand Huay Ka Yeang Stream 270 14.555 Thong Pha Phum District 1 98.597725 Hin Dat Subdistrict 7 104 1 1 Kanchanaburi 3411799348 2002-03-10 UMC R. Sites & Sites, A & K. Kirawanich Thailand 1220 16.983334 Pool 1280 101.0 Huai Khamin Noi Waterfall 7 104 1 1 Phitsanulok 3411799398 [151,944,151,177] 2002-05-22 UMC Team 8 105 1 1 3411799444 2003-07-12 THNHM N. Changthong 1280 16.983334 Waterwheel Falls 1280 101.0 8 105 1 1 3411799430 2002-11-15 UMC, THNHM Team 1280 16.983334 Waterwheel Falls 1280 101.0 8 105 3 3 3411799413 [790,990,223,249] 2002-11-15 UMC Team 1280 true 16.983334 Waterwheel Falls 1280 101.0 8 105 2 2 3411799312 2003-05-05 UMC N. Changthong 1280 true 16.983334 Waterwheel Falls 1280 101.0 8 105 1 1 3411799447 2011-03-23 KKU N. Sangpradub Noen Maprang District 894 16.485416 Thung Salaeng Luang Natl. Park 1 100.80867 Ban Mung Subdistrict 8 105 2 2