An investigation was carried out into the use of water traps for sampling Glossina morsitans submorsitans Newst. and G. tachinoides Westw. in Yankari Game Reserve in sub-Sudan savanna in northern Nigeria. The traps consisted of coloured trays filled with water plus small quantities of formalin and detergent. Colour was thought to be the major factor attracting flies to the traps, white traps being most effective for G. m. submorsitans and black ones for G. tachinoides. Water traps were compared with biconical traps, and both methods showed similar changes in catches in different vegetation types over a year. Males and females of both species showed a marked expansion in distribution in the rains and a contraction to riverine woodland in the dry season, though females of G. m. submorsitans could be caught in the adverse deciduous woodland and open savanna all year round. Water traps are considered a very cheap and practicable sampling method for ecological studies on these species of Glossina, providing specimens well preserved upon capture for later morphometric and analytical studies.