Hydrovatus sinister Sharp, 1890: 343; Biström, 1996: 521, and references therein; Balke et al., 1999: 325; Nilsson, 2001: 192.
Material examined. – 160 specimens - Central catchment area - 21 ex., Nee Soon Swamp Forest, 20 Sep.1993, y 843, coll. C. M. Yang (ZRC); 1 ex., idem, 26 Aug.1993, coll. K. L. Yeo (ZRC); 2 ex., Nee Soon Swamp Forest, 26 Aug.1992, coll. K. L. Yeo (ZRC); 1 ex., Nee Soon Swamp Forest, 16 May.1992, coll. C. M. Yang (ZRC); 38 ex., idem, 6 Dec.1996, coll. L. Hendrich (CBH, ZRC); 150 ex., idem, 21 Apr.1997, coll. M. Balke & L. Hendrich (CBH, ZRC); 8 ex., idem, 26 Apr.1997, coll. M. Balke, L. Hendrich & C. M. Yang (CBH). Sungai Buloh - 10 ex., Nature Park, pond, 5 Dec.1996, coll. L. Hendrich & A. Wong (CBH, ZRC). Other areas – 4 ex., Lorong Banir, pond 1, 14 Jul.1995, NS 200, coll. H. K. Lua (ZRC); 7 ex., Lorong Banir, pond 1, 28 Apr.1997, coll. M. Balke & L. Hendrich (CBH); 16 ex., Lorong Banir, pond 2, 16 Jun.1995, NS 191, coll. H. K. Lua (ZRC); 6 ex., Bukit Batok Nature Park, pond, 23 Apr.1997, coll. M. Balke & L. Hendrich (CBH).
Distribution. – Sri Lanka, India, Myanmar, Laos, West Malaysia, Indonesia [Sumatra, Kalimantan] (Biström, 1996) and Singapore (Balke et al., 1999).
Ecology. – The most common species of the genus in Singapore. Hydrovatus sinister is an inhabitant of shallow, muddy water of open swamps, artificial ponds (garden and park ponds, quarry ponds), and slow flowing irrigation ditches. The habitat is rich in rotten leaves, sedges and submerged plants.