A Mixed Population of Glossina morsitans and G. swynnertoni

Abstract

A system of marking has been designed whereby 25,000 tsetse-flies can be marked without duplication, using 2 different colors at a time. This obviates the need for re-marking on recapture. The information derived from such observations can be much increased if the catching points are spaced at equal intervals along an "angular spiral" path. Very satisfactory agreement was found, in an isolated block of bush, between estimates of Glossina morsitans and G. swynnertoni populations, made respectively by extrapolating from corrected recaptures, and without extrapolation from re-recaptures. The agreement proves that the catchers do not tend to select the marked flies. Survival of males of both spp. in the isolated block was short, and in the case of G. swynnertoni there was evidence that this was partly because flies were coming and going across the surrounding clearing, which contained much unburned trash. The 2 spp. were about equally "active", and "activity" (availability) of both rose in April, when few tenerals and females were caught and hunger was low. G. swynnertoni was always less hungry than G. morsitans.