The nutritional state of tsetse flies from different vegetation types in Rhodesia

Abstract

The nutritional state of males of Glossina morsitans Westw. (subsp. orientalis Vanderplank) obtained by two different methods from four vegetation types at two contrasted seasons during 1964–65 in Rhodesia was assessed by determining their fat content, haematin content and size. The results showed that even in the hot dry season, when Brachystgia and Commiphora woodlands were leafless, the nutritional state was better in flies from these two vegetation types than in those from evergreen riverine fringe vegetation; in the rainy season, the difference persisted but was smaller. Only in Combretum bushland, which is sparsely wooded, did the poor nutritional state of flies caught in both seasons accord with the relatively inhospitable appearance of this vegetation type.The total food-reserves (fat plus the fat-equivalent of haematin) were higher in flies captured on fly-rounds than in those captured on bait-oxen, but the difference was smaller in populations under nutritional stress, e. g., in flies from riverine fringe vegetation and Combretum bushland in the hot season, which suggests that the period of sexual appetitive behaviour in males is shortened under conditions of nutritional stress.The implications of these results are discussed in relation to methods of control that involve discriminating between parts of the tsetse habitat.