Study of a Natural Population of Glossina Fuscipes Fuscipes Newstead and a Model of Fly Movement

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David R.
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In recent years much interest has been expressed in the application of the sterile-male technique to the control of tsetse flies. Whilst, in the laboratory, certain aspects of the behaviour of sterilized flies may be profitably compared with those of their unsterilized relatives (Langley, Curtis & Brady 1974) other equally important characteristics affecting the success of the technique can only be determined from field studies. Among these are population distribution and movement. Undoubtedly previous conclusions of tsetse behaviour, derived from field studies, have been influenced by biased methods of attracting the populations of flies for capture (Pilson & Pilson 1967; Pilson & Mackenzie 1972), by non-random sampling of the flies thus attracted (Vale 1974a,b; Rogers & Smith 1977) and by doubtful interpretation of the results obtained. Most of these difficulties arise not from the bias of any sample but from ignorance of its extent, a difficulty only resolved when sampling methods have a precisely defined efficiency (Vale 1974a). When this has been measured even fairly simple sampling routines can be used with more confidence than has in the past been justified. For example, population studies of tsetse flies have often involved mark-release-recapture programmes carried out over large areas (Jackson 1948a, 1955). The recaptures obtained, whilst providing an estimate of population size, also give some idea of the nature and extent of fly movement. Such results are, however, open to a number of interpretations. On the one hand, they led Jackson to suggest (1930, 1941a) that flies use different parts of their habitat for feeding and breeding and restrict themselves to 'ambits' from which they rarely emigrate. The ambit of each fly was assumed to include both a feeding and breeding ground. But recently Bursell (1970) has put forward another interpretation of the same results and has suggested instead that flies move more or less at random within the boundary of their habitat. In contrast to Jackson's ambit theory, Bursell's random movement hypothesis accounts for the large initial movement away from a release point, followed by reduced later movement, without making any demands on the tsetse's ability to navigate in uniform habitats.
The Journal Of Animal Ecology, 46, p. 309-330