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 Regimbart, 1891 Regimbart 1891 [151,629,1554,1582] Insecta Gyrinidae Gyrinus Animalia Coleoptera 2 99 Arthropoda species smaragdinus  ( Figs. 1B, 2, 3C–E, 7A–B, 8A)   Material examined.   THAILAND: Chiang Mai Province: Doi Inthanon Natl. Park, Mae Klangat Ban Khun Klang, 18°31.259'N 98°31.310'E,  1296 ma.s.l.,  18.V.2004, leg. T. Prommi, A. Vitheepradit, P. Laudee& P. Thamasenanupap, L-694, 3 males, 9 females( UMC); same locality except for, Pha Dum Waterfall, 18°36'N 98°31'E,  1379 ma.s.l.,  3.V.2003, leg. UMC & CMU teams, L-499, 3 males, 2 females( UMC); same locality except for, Siriphum Waterfall(lowest level), 18°32'N 98°31'E,  1460 ma.s.l.,  21.III.2002, leg. R.W. Sites, A. Vitheepradit& K. Kirawanich, L-315, 4 males, 3 females( UMC); same locality except for,  9.V.2002, leg. UMC & CMU teams, L-401, 3 males( UMC); same locality except for, stream from Huai Sai Luang Waterfall, 18°31'N 98°27'E,  1060 ma.s.l.,  8.V.2002, leg. UMC & CMU teams, L-396, 27 males, 27 females( UMC);  Doi Suthep Natl. Park, Monthathan Waterfall, 18°49'N 98°55'E,  700 ma.s.l.,  11.I.2003, leg. CMU Team, 1 male( UMC); same locality except for,  14.II.2003, leg. CMU Team, 1 male( UMC);  Pondat Ban Buak Thoei, Pong Yaeng Subdistrict, Mae Rim District, 18°53'30.2"N 98°47'36.5"E,  1153 ma.s.l.,  29.IV.2018, leg. B. Suksai, S. Kullasoot, C. Yatfung& P. Sapewisut, 2 males, 1 female( THNHM).   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, 2 males( KKU, THNHM),  1 female( THNHM).   Loei Province: Phu Hin Rongkla Natl. Park, Man Daeng Noiat trail, 16°57'N 101°03'E,  1600 ma.s.l.,  5.V.2003, leg. N. Changthong, 20 males, 18 females( UMC); same locality except for,  1340 ma.s.l.,  6.V.2003, leg. A. Vitheepradit, T. Prommi& M.L. Ferro, L-504, 10 males, 16 females( UMC);  Phu Kradueng Natl. Park, stream from Tham Yai Waterfall, Si Than Subdistrict, Phu Kradueng District, 16°52'59.9"N 101°46'46.4"E,  1197 ma.s.l.,  7.XII.2010, leg. N. Sangpradub, 1 female( KKU); same locality except for, Tham Sor Nuo Waterfall, Si Than Subdistrict, Phu Kradueng District, 16°52'36.2"N 101°44'48.2"E,  1234 ma.s.l.,  8.III.2011, leg. N. Sangpradub, 1 male, 1 female( THNHM); same locality except for, Wang Kwang Waterfall, Si Than Subdistrict, Phu Kradueng District, 16°53'29.5"N 101°47'03.5"E,  1221 ma.s.l.,  6.III.2011, leg. N. Sangpradub, 2 females( KKU).   Nan Province: Doi Phuka Natl. Park, Ton Thong Waterfall, 19°12'N 101°04'E,  900 ma.s.l.,  21.IV.2003, leg. A. Vitheepradit, T. Prommi& K. Setaphan, L-472, 4 males, 1 female( UMC); stream at Khun Sathan Natl. Park, Ban Mueng Li, Mueng Li Subdistrict, Na Muen District, 18°15'08.4"N 100°29'35.8"E,  786 ma.s.l.,  29.V.2017, leg. P. Sapewisut, 1 male, 1 female( THNHM).   Phitsanulok Province: Phu Hin Rongkla Natl. Park, stream btw Rd2113 and Man Daeng Waterfall,  12.VI.1998, leg. R.W. Sites& K.B. Simpson, L-187, 22 males, 17 females( UMC); same locality except for, Waterwheel fallsand stream, 16°59'N 101°00'E,  1280 ma.s.l.,  10.II.2003, leg. CMU Team, 6 males, 4 females( UMC); same locality except for,  6.V.2003, leg. A. Vitheepradit, T. Prommi& M.L. Ferro, L-506, 2 males, 3 females( UMC); same locality except for,  12.VII.2003, leg. N. Changthong, 1 male, 3 females( 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, 1 male, 1 female( KKU).   Diagnosis.Male ( Fig. 1B): Size: 4.0–5.0 mm. Body form oval, strongly convex in lateral view; pronotum and elytral margins darkly colored, pronotum with median transverse depression ( Fig. 2A), dorsal surface strongly iridescent, without evident microreticulation; pronotum and elytra laterally without bronzy-metallic sheen; striae I–XI evident with distinct, widely spaced punctures, striae VI–X strongly sulcate ( Fig. 2B); elytral intervals VII–X convex; elytral apex truncate ( Figs. 1B, 2B–C), without border ( Fig. 2C), epipleural angle indistinct; metaepisternal ostiole small; aedeagus with median lobe slightly shorter than parameres, apical half of median lobe broader in width than single paramere, apex weakly triangular, lateral margin of parameres weakly curved, apex rounded ( Figs. 3C–D). Female: Similar to male but with a more oval body form; gonocoxae as in Fig. 3E.   FIGURE 3.Aedeagus and gonocoxae: (A–B)  Gyrinus sericeolimbatus: (A) aedeagus, dorsal view (after Svensson 1991; Mazzoldi 2010); (B) gonocoxae, ventral view, scale bars = 0.5 mm; (C–E)  Gyrinus smaragdinus: (C–D) aedeagus, scale bars = 0.5 mm: (C) dorsal view; (D) lateral view; (E) gonocoxae, ventral view, scale bars = 0.5 mm.  Differential diagnosis.Among the Old World  Gyrinus,  G. smaragdinusis closest to  G. ignitus Régimbart, 1895, a Malagasy endemic species. The only other species of  Gyrinusrecorded from Thailandis  G. sericeolimbatus. G. smaragdinuscan be distinguished from  G. sericeolimbatusby its iridescent appearance and strongly sulcate lateral elytral setriae.   Distribution.This species is known from northeastern India, to Myanmar, Yunnan Provinceof southern China, and northern Vietnam( Ochs 1930; Vazirani 1972, 1984; Mazzoldi 1995). It is here recorded for the first time in Thailand.  Habitat.We found  G. smaragdinusmost often on stagnant water of montane streams and ponds at high elevation, ranging from 700 to 1600 ma.s.l. ( Figs. 7A–B). Only a few specimens were found in a stream at a low elevation ( 270 ma.s.l.).   Discussion.  G. smaragdinusis the only species of  Gyrinusthat we encountered during our sampling in the northern, western and northeastern regions of Thailand( Fig. 8A). The first author found this beetle in a pond surrounded by land with both agricultural use and intact forest. 3411799373 2004-05-18 UMC T. Prommi & A. Vitheepradit & P. Laudee & P. Thamasenanupap Thailand Doi Inthanon Natl. Park 1296 18.520983 Ban Khun Klang 1 98.521835 Mae Klang 2 99 12 9 3 Chiang Mai 3411799397 2003-05-03 UMC & CMU team Thailand Doi Inthanon Natl. Park 1379 18.6 Pha Dum Waterfall 1275 98.51667 Mae Klang 2 99 5 2 3 Chiang Mai 3411799309 2002-03-21 UMC R. W. Sites & A. Vitheepradit & K. Kirawanich Thailand Doi Inthanon Natl. Park 1460 18.533333 Siriphum Waterfall 1275 98.51667 Mae Klang 2 99 7 3 4 Chiang Mai 3411799451 2002-05-09 UMC & CMU teams Thailand Doi Inthanon Natl. Park 1460 18.533333 Siriphum Waterfall 1275 98.51667 Mae Klang 2 99 3 3 Chiang Mai 3411799384 2002-05-08 UMC & CMU teams Thailand Doi Inthanon Natl. Park 1060 18.516666 Huai Sai Luang Waterfall 1275 98.45 Mae Klang 2 99 54 27 27 Chiang Mai 3411799374 2003-01-11 UMC Team Thailand 700 18.816668 Monthathan Waterfall 1274 98.916664 Doi Suthep Natl. Park 2 99 1 1 Chiang Mai 3411799341 2003-02-14 UMC Team Thailand 700 18.816668 Monthathan Waterfall 1274 98.916664 Doi Suthep Natl. Park 2 99 1 1 Chiang Mai 3411799434 2018-04-29 THNHM B. Suksai & S. Kullasoot & C. Yatfung & P. Sapewisut Thailand Pond 1153 4 101 18.891722 Pong Yaeng Subdistrict 1 98.79347 Ban Buak Thoei 2 99 3 1 2 Chiang Mai 3411799339 2002-02-25 KKU, THNHM S. Saeheag Thailand Thong Pha Phum Natl. Park 270 14.555 Hin Dat Subdistrict 1 98.597725 Huay Ka Yeang Stream 4 101 2 2 Kanchanaburi 3411799366 [431,658,1301,1327] 2002-02-25 THNHM S. Saeheag Thailand Thong Pha Phum Natl. Park 270 true 14.555 Hin Dat Subdistrict 1 98.597725 Huay Ka Yeang Stream 4 101 1 1 Kanchanaburi 3411799453 2003-05-05 UMC N. Changthong Thailand 1600 16.95 Man Daeng Noi 1280 101.05 Phu Hin Rongkla Natl. Park 4 101 38 18 20 Loei 3411799405 2003-05-06 UMC A. Vitheepradit & T. Prommi & M. L. Ferro Thailand 1340 16.95 Man Daeng Noi 1280 101.05 Phu Hin Rongkla Natl. Park 4 101 26 16 10 Loei 3411799359 2010-12-07 KKU N. Sangpradub Thailand Phu Kradueng Natl. Park 1197 16.883307 Si Than Subdistrict 1 101.77956 Tham Yai Waterfall 4 101 1 1 Loei 3411799415 2011-03-08 THNHM N. Sangpradub Thailand Tham Sor Nuo Waterfall 1234 16.876722 Phu Kradueng District 1 101.74672 Si Than Subdistrict 4 101 2 1 1 Loei 3411799331 2011-03-06 KKU N. Sangpradub Thailand Wang Kwang Waterfall 1221 16.891527 Phu Kradueng District 1 101.7843 Si Than Subdistrict 4 101 2 2 Loei 3411799327 2003-04-21 UMC A. Vitheepradit & T. Prommi & K. Setaphan Thailand 900 19.2 Ton Thong Waterfall 1273 101.066666 Doi Phuka Natl. Park 4 101 5 1 4 Nan 3411799304 2017-05-29 THNHM P. Sapewisut Thailand Khun Sathan Natl. Park 786 18.252333 Mueng Li Subdistrict 1 100.49327 Ban Mueng Li 4 101 2 1 1 Nan 3411799362 1998-06-12 UMC R. W. Sites & K. B. Simpson Thailand Phu Hin Rongkla Natl. Park Man Daeng Waterfall Rd 4 101 39 17 22 Phitsanulok 3411799382 2003-02-10 UMC Team Thailand Phu Hin Rongkla Natl. Park 1280 16.983334 Waterwheel falls 1280 101.0 Rd 4 101 10 4 6 Phitsanulok 3411799311 2003-05-06 UMC A. Vitheepradit & T. Prommi & M. L. Ferro Thailand Phu Hin Rongkla Natl. Park 1280 16.983334 Waterwheel falls 1280 101.0 Rd 4 101 5 3 2 Phitsanulok 3411799303 [467,1432,1841,1868] 2003-07-12 UMC N. Changthong Thailand Phu Hin Rongkla Natl. Park 1280 16.983334 Waterwheel falls 1280 101.0 Rd 4 101 4 3 1 Phitsanulok 3411799442 2011-03-23 KKU N. Sangpradub Thailand Thung Salaeng Luang Natl. Park 894 16.485416 Ban Mung Subdistrict 1 100.80867 Tum Din Stream 4 101 2 1 1 Phitsanulok