Experiments in Grass Fires against Glossina morsitans in Southern Rhodesia

Extract

1. An account is given of two organised grass fires carried out in the Lomagundi fly-belt of Southern Rhodesia in the years 1927 and 1928, as a method of controlling G. morsitans.

2. The effect of these fires on the flora and game is described, and details given of the immediate effect of these fires on both the adult fly and the puparia. The effect on the adult fly was to concentrate it along the shady watercourses and other parts of the forest where the fires were less fierce and the requisite shade was to be found.

3. On the puparia, no immediate effect was noticeable. The number of dead puparia collected increased during October and November, and this is considered to be attributable to the lethal effects of the sun, not of the fire.

4. The pupal period of the fly decreases from eighty-two days for puparia collected in June, to twenty-one days for puparia collected in November. The period of greatest activity of the fly, as indicated by emerging flies, density and collected puparia, is in September.

5. A short account is given of the trypansome infection and food of the fly. On the average 11 per cent. of the flies are infected with pathological trypansomes in the proportion of ten congolense group to seven vivax group. Only one infection of the gland was found out of 1,523 dissections. There is a tendency for the percentage of infected flies to increase during the late dry season. This rise coincides with the increased visibility of the game. Examination of the fat content failed to indicate any degree of starvation amongst the flies.

The food of the fly consists almost entirely of mammalian blood, only one case of avian blood being found.

6. A final decision has not yet been pronounced upon the efficacy of grass fires as a means of controlling G. morsitans in Southern Rhodesia.