• Glossina;
  • model;
  • mortality;
  • tsetse

Tsetse exhibit a U-shaped age–mortality curve, with high losses after eclosion and a well-marked ageing process, which is particularly dramatic in males. A three-parameter (k1k3) model for age-dependent adult instantaneous mortality rates was constructed using mark–recapture data for the tsetse fly Glossina morsitans morsitans Westwood (Diptera: Glossinidae). Mortality changed linearly with k1 over all ages; k2 affected only losses in roughly the first week of adult life, and k3 controlled the ageing rate. Mortality pooled over age was twice as sensitive to changes in k3 as in k1. Population growth rate was, however, similarly affected by these two parameters, reflecting the disproportionate effect of k3 on mortality in the oldest flies that contribute least to the growth rate. Pooled-age mortality and growth rate were insensitive to changes in k2. The same model also provided good fits to data for laboratory colonies of female G. m. morsitans and Glossina austeni Newstead and should be applicable to all tsetse of both sexes. The new model for tsetse mortality should be incorporated into models of tsetse and trypanosome population dynamics; it will also inform the estimation of adult female mortality from ovarian dissection data.