[It is not usually found far from water, requiring a humid atmosphere and temperature of about 85° F. (shade). But a marked seasonal distribution is shown, the flies considerably extending their range during the rainy season, and thus visiting districts which are dry for the greater part of the year; as the rains diminish the fly gradually leaves the temporary haunts and returns to the more permanent ones. It bites only by day, and then only in sunny weather, and usually lives in shade.
[Roubaud has shown that the first larva produced is about three weeks after copulation, and that others are produced at an interval of nine or ten days. The puparium stage is rapidly produced after the expulsion of the larva, often in three-quarters of an hour. The puparium stage lasts from thirty-two to thirty-five days. The puparia occur in well-drained humus close to water, sheltered by trees or bushes, in crevices in rocks, and between the exposed roots of trees, sometimes in sand.
[Bruce has shown that only a very small percentage of flies fed experimentally on infected animals ultimately become infective, and that the infectivity of this small percentage depends upon a delayed infection of the salivary glands.
[A variety, wellmani of Austen, is found in Angola, Gambia, the Katanga district of the Congo Free State, the Matondwi Islands of Tanganyika, etc.
Glossina morsitans, Westwood.
[This species has been shown by Kinghorn and Yorke, and also by Bruce, to be responsible for the transmission of Trypanosoma rhodesiense, the micro-organism producing sleeping sickness in man in Rhodesia and Nyasaland and also in parts of German and Portuguese East Africa. Fisher and Taute have demonstrated experimentally that Trypanosoma gambiense—the sleeping sickness parasite of other parts of Africa—may also be transmitted by this fly, and in addition it is known to be capable of disseminating several species of trypanosomes pathogenic to animals. Of these, T. brucei (=? T. rhodesiense), the parasite of tsetse disease, first incriminated by Bruce, is perhaps the most important.
Fig. 420.—The tsetse-fly (Glossina morsitans, Westwood).
[It is the most widely spread of all tsetse-flies; its range extends from Senegambia in the north-west to Southern Kordofan and Southern Abyssinia in the north-east, and then southwards to the Bechuanaland Protectorate, North-eastern Transvaal and Zululand. The actual localities given by Austen are Gambia, French Guinea, Gold Coast, Togoland, Dahomey, Northern Nigeria, Congo Free State, the Bahr-el-Ghazal, the Uganda Protectorate, German East Africa, and Portuguese East Africa.