Age determination for female tsetse flies and the age compositions of samples ofGlossina pallidipesAust.,G. palpalis fuscipesNewst. andG. brevipalpisNewst.

Abstract

The age compositions of samples of females ofGlossina pallidipesAust.,G. palpalis fuscipesNewst. andG. brevipalpisNewst., are analysed by means of a method of age determination based upon the changes occurring in the reproductive system during successive gonotrophic cycles. This method of age determination is described in detail.Females were sampled by three main methods: in traps, by catching on a bait-animal, and on a fly-round. Some flies were also found as resting flies in the undergrowth.Trap-caught samples ofG. pallidipeswere older (i.e.), contained a larger proportion of old flies (and a smaller proportion of young flies) than the hand-caught samples. The bait-caught samples were intermediate in age structure. Correlated with the increasing mean age in the hand-caught—bait-caught—trap-caught series was an increase in the proportion of females carrying third-instar larvae and a decrease in the proportion of those carrying eggs. Results with samples ofG. palpalis fuscipesandG. brevipalpiswere not so well defined.The results of dissecting teneral and non-teneral nullipars ofG. pallidipesandG. palpalis fuscipesindicate that females of the latter are inseminated some time before they take their first blood-meal, but teneral females ofG. pallidipesare inseminated when they come to the host to feed or after they have fed.The relation of the ovarian method of age determination to Jackson's (1946) wing-fray categories in females ofG. pallidipes, and the probable epidemiological importance of the samples, are also discussed.