The paper presents a way of estimating average daily mortality rates of female tsetse from ovarian age distributions. This technique was applied to monthly biconical trap samples of G. palpalis taken during and after insecticidal campaigns in the Bouaflé region of Ivory Coast. A clear inverse relationship is demonstrated between the annual mean number of females per trap per sample at 10 separate sites, and the mean annual mortality rates calculated for them. Local variation in the impact of insecticides is explained in terms of the grouping of the sites either side of a level of natural mortality above which tsetse populations cannot be sustained through reproduction alone.
A theoretical model for density dependent population growth is presented and applied to a particular control situation, that of the sterile insect release method. The model demonstrates that the effectiveness of any particular level of induced sterility (or mortality) is crucially determined by the natural resilience of the target population.
