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

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Abstract
A mark-release-recapture study of a natural population of G. f. fuscipes Newstead in the South Busoga district of Uganda is described. A feeding interval of about 4 days for male flies is estimated from the fairly regular peaks obtained in the recapture rate at 1 particular point in the area. There is a daily loss of 21% of marked flies from the area surrounding the point of marking and release. The distribution of the population of flies is related to the amount of light reaching any particular area and hence is determined by the vegetational cover. The concentration of recapture decreases regularly with distance from the point of marking and release. It is suggested that this is the result of random movement of flies after release. A simulation model that mimics the field situation is described and a comparison of its predictions with the field result suggests that male G. fuscipes move at an average rate of 370 yd (338 m)/day. There is no strong evidence that flies are relatively inactive for long periods during the 1st weeks of life, nor that they are restricted to ambits. Examples of advances of tsetse fly belts into favorable country are analyzed assuming that the movement was random. The calculated average daily displacement is 276 yd (252 m) and, considering the flight capabilities of these insects, shows relatively little variability. The random model is extended to describe the movement of flies within a day. It is suggested that of the 2 alternative methods for varying the total daily displacement the tsetse fly has a reasonably constant step length and varies the number of steps carried out. The importance of random movement in control measures is outlined. Movement can be quantified and hence can now be included in models for insecticidal and biological control.

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