Key to the species of Ptilomerinae (Hemiptera: Heteroptera: Gerridae) of Thailand and review of the fauna of the Tennaserim Mountain Range Author Raruanysong, Sajeemat Author Vitheepradit, Akekawat Author Sites, Robert W. text Zootaxa 2014 3852 1 101 117 journal article 10.11646/zootaxa.3852.1.4 527bebc8-3c9d-4353-b991-c92a913ee7dd 1175-5326 230500 D0876B07-5E29-4D4F-BFB4-968CFBA5BCE1 Pleciogonus wongsirii Chen, Nieser , & Wattanachaiyingcharoen Figs. 4 , 42 Pleciogonus wongsirii Chen, Nieser, & Wattanachaiyingcharoen 2002 : Tijdschr. Entomol. 201–212. Diagnosis. This species can be recognized by the elongate body and predominantly yellow coloration with a dark pattern in the middle ( Fig. 4 ). Antennal segment 1 is distinctly longer or subequal to segments 2 to 4 combined. The parameres are bent basally with long hairs on the apical 1/3 ( Fig. 42 ). The mesotibia has long swimming hairs. This species can be distinguished from members of closely related genera as given in the key to genera. Discussion. This species has been recorded previously from only the northern region (Chiang Mai, Chiang Rai, and Lumpang provinces) (Chen et al. 2002). In this study, this species was collected from Kanchanaburi, Prachuap Khiri Khan, and Ratchaburi provinces. Chen et al. (2002) provided biological information for this species and indicated that it could be collected from shaded mountain streams in mesohabitats where other rheophilic bugs occur. In our study, both adults and nymphs of P . wongsirii were usually found on the lee side of rocks in streams. When they were pursued, they jumped off the rock and glided away, but returned to the same place within approximately one minute. Adults of this species were observed to glide on the water surface with a zigzag movement when they were pursued, which is similar to the behavior of adult Pleciobates . Females of P . wongsirii exhibit morphological variation between populations north of the Isthmus of Kra and in the Isthmus of Kra . More specifically, females north of the Isthmus of Kra have long connexival spines, whereas those in the Isthmus of Kra have very short spines. We have a female specimen from Prachuap Khiri Khan Province, just north of the Isthmus of Kra , with connexival spines of intermediate length. Nonetheless, close examination of male genitalic structures of those populations indicates the shape of parameres is consistent throughout the northern and southern populations. Material examined. THAILAND : Kanchanaburi Province: Amphur Sai Yok, Thong Pha Phum Reforestation Station, Mae Nam Noi, 14º31'N 98º37'E , 204 m , 12-IV-2002 , UMC and CMU teams, L-335 ( 1 male , 1 female ); Amphur Thong Pha Phum, Heuy Ka Yaeng at Ban Padsadoo Klang, 14º33'N 98º34'E , 296 m , 9-IV-2003 , Sites, Vithepradit, Prommi and Sataphan, L-457 ( 1 male , 9 females ); Amphur Sankhla Buri, Heuy Li Jia, 15º04'N 98º33'E , 169 m , 12-V-2003 , Vitheepradit, Prommi and Ferro, L-526 ( 4 males , 2 females ); Amphur Thong Pha Phum, Heuy Ka Yaeng at Ban Padsadoo Klang, 14º33'N 98º34'E , 296 m , 26-V-2003 , Vitheepradit and Prommi, L- 717 ( 3 males , 22 females ); Amphur Sangkhla Buri, Heuy Li Jia, 15º04'N 98º33'E , 169 m , 26-V-2004 , Vitheepradit and Prommi, L-718 ( 4 males , 14 females ); Amphur Sangkhla Buri, Heuy Li Jia, 15º04'N 98º33'E , 169 m , 5-VI- 2006 , Sites, Vitheepradit and Prommi, L-917 ( 6 males , 8 females ); Thong Pha Phum NP, Heuy Pak Khok, 14º38.738'N 98º31.374'E , 187 m , 25-XI-2006 , C-6 ( 1 male ); Lam Khlong Ngu NP, Heuy Li Jia, 15º04'N 98º33'E , 169 m , 26-XI-2010 , KU team, C-9 ( 4 males , 16 females ); Heuy Clity, 14º57.717'N 98º54.552'E , 674 m , 26-XI- 2010 , KU team, C-10 ( 1 male , 3 females ); Thong Pha Phum NP, Jog Kradin Waterfall, 14º41'N 98º23'E , 23-I-2013 , KU team, C-258 ( 1 male ); Prachuap Khiri Khan Province: Amphur Bang Saphan, Sai Koo Waterfall, 11º14'N 99º20'E , 73 m , 18-V-2003 , Vitheepradit and Ferro, L-545 ( 1 female ); same locality, 28-V-2004 , Vitheepradit and Prommi, L-722 ( 10 males , 12 females ); same locality, 21-I-2013 , KU team, C-255 ( 11 males , 5 females ); Ratchaburi Province: Amphur Suan Phueng, Nam Tok Kao Chan Waterfall, 13º31'N 99º14'E , 159 m , 17-IV-2002 , Vitheepradit and Kirawanich, L-349 ( 1 male ); Nam Tok Kao Chan Waterfall, 13º31.461'N 99º14.387'E , 204 m , 13- XI-2012 , KU team, C-87 ( 1 male ).