Hydrachna testudinata Cook, 1967

Material examined. 1/0/0, Phan Reservoir, Udon Thani Province, Thailand, 17° 50.052ʹ N, 103° 04.356ʹ E, 31-i-2011 ; 1/0/0, Nong Ya Ma Reservoir, Roi-Et Province, 16° 01.783ʹ N, 103° 40.894ʹ E, 12-ii-2011 ; 0/1/0, pond next to Science Faculty building, Mahasarakham University, 16° 14.868ʹ N, 103° 15.014ʹ E, 2-xi-2016 .

Remarks. The female from this study is 910 long and 925 wide, smaller than the measurements given by Cook (1967) and Lundblad (1969). Left and right fourth coxae differ in shape, the left coxae wider than the right coxae. Our female specimen is morphologically similar to H. testudinata . The species is known from India and Burma, and is reported here for the first time for Thailand.