44 



CHAPTER V. 



" FLY-BELTS," OR AREAS IN WHICH THE DIFFERENT SPECIES OF 

 TSETSE ARE FOUND. 



" In those parts of Africa in which Tsetse-flies occur they are not 

 found everywhere, but are generally confined to particular tracts, which 

 are known as ' Fly-belts/ and are often of very limited extent. We are 

 still somewhat in the dark as to the factors that determine the limits 

 of these ' belts/ 1 but, although Tsetse are undoubtedly dependent 

 upon the blood of vertebrates for their continued existence, all recent 

 evidence goes to show that the most important element is the physical 

 character of the locality, and, probably, its suitability as a breeding 

 ground. As a general rule it may be said that Tsetse-flies are usually 

 met with in damp, hot localities, either on the borders of rivers or 

 lakes, or at any rate not far from water ; this, however, applies more 

 especially to the species belonging to the Glossina palpalis group ; 

 other Tsetse-flies, especially those of the Glossina morsitans group, 

 are often found at a considerable distance from water. Cover, in the 

 shape of more or less thick bush or forest, shady trees, or reeds, is 

 essential, and Tsetse-flies are absent from open grass plains " (Austen, 3) 



We will now give, as concisely as possible, a rapid review of the 

 essential facts already ascertained as to the habitats of the different 

 species of Glossina. For fuller information upon this subject the 

 reader should consult the Bibliography at the end of this volume, 

 (see pp. 165-178). 



Glossina palpalis, Rob.-Desv. As is well known, this Tsetse-fly 

 haunts the margins, overgrown with vegetation, of rivers, streams, 

 watercourses, pools, lakes and marshes in the low-lying, humid 

 countries of Tropical Africa ; and, unless it has followed human beings 

 or animals, it is rarely met with more than some 30 yards from water. 

 Fiske, however (54), writing after many years' study of G. palpalis 

 in the islands in, and on the mainland shore of Lake Victoria, Uganda, 

 considers it " pure coincidence that the insect is never found far from 

 water," and asserts his confident belief " that it would exist, and that 

 it will be found eventually to exist, in any inland localities wiiere host 

 animals of favoured species occur in well sheltered areas provided with 

 suitable breeding places." On another page of the same paper this 

 authority writes : " Every bit of evidence that has been gathered 

 supports this final conclusion concerning the range of fly inland from 

 the lake shore ; it is primarily controlled by the distribution of host 

 animals, and there is nothing to indicate that this tsetse requires open 

 water or humid conditions, or that water is even attractive to it. Its 

 favoured hosts are amphibious in habit ; the most attractive types of 

 shelter occur more commonly near the shore than inland ; and it 

 rarely finds good breeding places elsewhere." As regards the character 

 of the shelter needed by this species Fiske remarks : " Two kinds of 

 shelter are requisite, (a) light, such as serves at breeding grounds and 



1 In this connection Mr. R. W. Jack (74), writing with reference to G. morsitans. 

 in Southern Rhodesia, in 1918, stated that observations show that the dispersing 

 range of this species does not exceed two or three miles, but that there is no 

 apparent reason for this limited migration unless it be a definite instinct >to avoid 

 wandering. The males may be carried in any direction up to ten miles and more- 

 by the movements of animals and human beings, but there is a marked tendency 

 to return to their place of origin. 



