An artificially isolated Generation of Tsetse Flies (Diptera)

Abstract

A generation ofGlossina morsitanswas artificially isolated by allowing emergence for three days in the habitat ofG. swynnertoniandG. pallidipes.Most teneral flies (with chitin unhardened before their first meal) were active on day 2 to 4 from emergence. The non-teneral flies first appeared in numbers when a week old. It is possible that they were somewhat inactive while still fairly young, that is, up to two or three weeks, but this was not proved. They are definitely inactive between the first and second meals. The females, on the other hand, are much more active in the first three weeks of life than later on.The teneral males contained about 12 mg. water, which was increased after several meals to a maximum of about 18 mg. by day 17. Fat started at a mean of 1 1/2 mg., declining to 1 mg. at the first meal, then rising to about 3 mg. at day 17, after which there was no further increase. Residual weight behaved like the water, except that it was relatively very low in teneral flies. The hungry flies which reappear after the first meal have also a relatively low residual weight.In this experiment there was no evidence that smaller flies were at a disadvantage, as has been suspected from other work.With reservations concerned with differences in place and time, the mean age of samples of male flies can be accurately deduced from the wear on the trailing margin of the wing. The females do not wear out their wings so quickly.Males dispersed, in any one direction, to a mean perpendicular distance of 365 yards in a week, 484 yards in two weeks, 772 yards in three weeks, and 941 yards in four weeks.In spite of undoubted interference byG. swynnertoni, a considerable second generation appeared.The females and pupae in nature experienced temperatures approximating to those obtained in a screen at a standard meteorological station: they did not live in specially cool eeoclimates.