| The responses of G. f. fuscipes and other Diptera
to carbon dioxide were studied in linear and dense forests along the shores of Lake
Victoria, Kenya, in 1996-97. Flies were caught in biconical traps and were intercepted
with electric nets while in flight near traps. Carbon dioxide dispensed at a high rate (5
litre min-1) in linear forest failed to increase the numbers of tsetse
attracted to or caught in traps. In contrast, catches of non-biting Muscidae, Stomoxyinae
and Tabanidae were improved by up to 11 times. Inside dense forest, carbon dioxide
released at half this rate increased both the numbers of female tsetse attracted to a trap
and the catches in a trap by about 2-3 times. Catches of male tsetse were, however, not
affected. Striking improvements for other Diptera were also seen (up to 102 times). Under
a variety of conditions, unbaited biconical traps attracted many Diptera to the vicinity
of a trap, but caught few flies due to low capture efficiencies (typically <10%). In
contrast, efficiency estimates for G. f. fuscipes were good, varying from 37 to 82%
in different habitats and seasons. These results are discussed in relation to the search
for practical odour attractants for riverine tsetse. |