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 (Fabricius, 1775) Fabricius 1775 [151,593,223,250] Insecta Gyrinidae Dineutus Animalia Coleoptera 6 103 Arthropoda species australis  ( Figs. 1C–D, 4A, 5A–E, 7C, 8A)   Material examined.   THAILAND: Chiang Mai Province: Doi Inthanon Natl. Park, Mae Klang Waterfall, 18°29'N 98°40'E,  415 ma.s.l.,  3.IV.2002, leg. CMU Team, 1 female( GTGC).   Khon Kaen Province: Chum Pae District, 16°34.585'N 102°01.668'E,  415 ma.s.l.,  3.V.2004, leg. A. Vitheepradit, L-660, 1 female( GTGC).   Nakhon Ratchasima Province: Sakaerat Environmental Research Station, Bonweir, U-dom Sap Subdistrict, Wang Nam Khiao District, 14°29'49.2"N 101°54'55.5"E,  472 ma.s.l.,  22.II.2014, leg. B. Suksai, 1 male( KKU); same locality except for,  29.III.2018, leg. P. Chanteenok, 1 female( KKU); same locality except for,  8.IV.2018, leg. B. Suksai, O. Pornsophon, T. Jantaranakee& S. Phengsalung, 2 males, 2 females( THNHM).   Phang Nga Province: Ban Bang Klag Klang, Koag Kien Subdistrict, Takua Pa District, 8°52.469'N 98°22.679'E,  17 ma.s.l.,  4.I.2006, leg. A. Vitheepradit, R.W. Sites& T. Prommi, L-881, 1 male( UMC).   Prachuap Khiri Khan Province: Ban Fah Pa Tarn, Hua Hin District, 12°31.810'N 99°32.062'E,  149 ma.s.l.,  28.V.2004, leg. A. Vitheepradit& T. Prommi, L-723, 1 male( UMC); same locality except for, Bue Sawan Stream, Huay Yang Subdistrict, Thap Sakae District, 11°40'29.4"N 99°36'02.4"E,  208 ma.s.l.,  23.V.2017, leg. B. Suksai& C. Yatfung, 1 female( THNHM).   Diagnosis.Male ( Fig. 1C): Size: 7.6–8.2 mm. Body form oval; apex of flagellomere VI darkly colored; elytral apices obliquely truncate with epipleural spines and serrations present ( Figs. 1C, 5A); lateral marginal of pronotum and elytron black to brown; protrochanter apically with patch of thick setae on ventral surface ( Fig. 4A); profemur without sub-apicoventral tooth; protibia wedge-shaped; venter black, epipleura brownish; aedeagus ( Figs. 5C–D) with median lobe slightly shorter than parameres, swollen in basal 1/9, strongly narrowed after basal 1/9, apex with tip strongly pointed, weakly curved ventrally in lateral view. Female ( Fig. 1D): Similar to male except for size: 8.1–8.2 mm; elytral apices truncate without epipleural spines ( Figs. 1D, 5B), protrochanter apically without patch of thick setae on ventral surface; gonocoxae ( Fig. 5E) elongate, lateral margin expanded and weakly rounded, apex nearly straight.  Differential diagnosis.  Dineutus australisis closest to  D. unidentatus, which also is found in Thailand, and can be distinguished from all other species of  Dineutusin this country by the protrochanter of the male having a distinct patch of setae. Both sexes of  D. australiscan be distinguished from those of  D. unidentatusby the oval body form and larger size, whereas in  D. unidentatusthe body is narrowly oval ( Fig. 1G) and smaller (6.0– 6.9 mm). The elytral apices of males of  D. australishave weak epipleural spines, whereas in the males of  D. unidentatusthese are longer and more developed ( Fig. 6A). In dorsal view, the aedeagus of  D. australisis distinct from that of  D. unidentatus, as the median lobe is very narrow and without a constricted apex ( Fig. 5C), in comparison to the broader, more parallel-sided median lobe of  D. unidentatus, which is abruptly constricted at its apex ( Fig. 6B). The females of  D. australiscan be distinguished from those of  D. unidentatusby the elytral apices lacking epipleural spines, which are presented in  D. unidentatus. The reproductive tract of  D. australishas broader gonocoxae with the apex nearly straight, whereas in  D. unidentatusthe gonocoxae are more elongate, with the apex obliquely truncate and the lateral angle acuminate.   Distribution. This species is widely distributed in the Oriental and Australian Regions. It has been recorded from China, Taiwan( Mazzoldi 1995); the Philippines( Ochs 1924; Freitag et al.2016); Japan( Takizawa 1931); Indonesia( Ochs 1949, 1953): Java, Bali, Lombok, Sumba, Sulawesi, Buru; New Guinea( Ochs 1955), Australia( Ochs 1949; Watts & Hamon 2010); New Caledonia( Satô 1966; Mazzoldi 2010); and the Pacific Islands: Vanuatu( Watts & Hamon 2010) and Fiji( Ochs 1949). This is the first time it has been recorded in Thailand.  Habitat.In Australia,  D. australishas been found in reservoirs, swamps, and pools in rivers and streams ( Watts & Hamon 2010). In the present study, BS collected  D. australison the water surface of ponds in the forest ( Fig. 7C) where it occurred among aquatic plants in shallow water. Additionally, it was found in shallow, stagnant streams.   Discussion.Within Thailand, it was found in the northern, northeastern, western, and southern regions ( Fig. 8A) and was collected at low elevations ranging from 17–472 ma.s.l. It co-occurred with  D. unidentatusand  D. spinosusin ponds. 3411799381 2002-04-03 GTGC Team Thailand 415 18.483334 Mae Klang Waterfall 1275 98.666664 Doi Inthanon Natl. Park 6 103 1 1 Chiang Mai 3411799410 2004-05-03 GTGC A. Vitheepradit Thailand 415 16.576416 Chum Pae District 1 102.0278 6 103 1 1 Khon Kaen 3411799353 2014-02-22 KKU B. Suksai Thailand Sakaerat Environmental Research Station 472 14.497001 Sap Subdistrict 1 101.91542 Bon 6 103 1 1 Nakhon Ratchasima 3411799360 2018-03-29 KKU P. Chanteenok Thailand Sakaerat Environmental Research Station 472 14.497001 Sap Subdistrict 1 101.91542 Bon 6 103 1 1 Nakhon Ratchasima 3411799345 2018-04-08 THNHM B. Suksai & O. Pornsophon & T. Jantaranakee & S. Phengsalung Thailand Sakaerat Environmental Research Station 472 14.497001 Sap Subdistrict 1 101.91542 Bon 6 103 4 2 2 Nakhon Ratchasima 3411799406 2006-01-04 UMC A. Vitheepradit & R. W. Sites & T. Prommi Thailand Ban Bang Klag Klang 17 8.874483 Takua Pa District 1 98.37798 Koag Kien Subdistrict 6 103 1 1 Phangnga 3411799347 2004-05-28 UMC A. Vitheepradit & T. Prommi Thailand 149 12.530167 Hua Hin District 1 99.53437 Ban Fah Pa Tarn 6 103 1 1 Prachuap Khiri Khan 3411799436 2017-05-23 THNHM B. Suksai & C. Yatfung Thailand Bue Sawan Stream 208 11.674833 Thap Sakae District 1 99.60066 Huay Yang Subdistrict 6 103 1 1 Prachuap Khiri Khan