XVI] 



BIONOMICS 



261 



atmosphere. The same observer remarks on the predilection of 

 the fly for the neighbourhood of fords and those parts of the 

 river most frequented by man. 



There is no record of G. palpalis from a greater altitude than 

 4000 feet, but it is common on the shores of Lake Victoria at 

 a height of 3700 feet. Such an altitude is exceptional, however, 

 and in most parts of Africa it is not found at so high a level,' 

 probably owing to the unsuitable climatic conditions" 



Fig. 67. \'iew on the River Gambia beyond Barijali shewing tlie dense nature 

 of the vegetation, which consists of Ferns, Palms, Pandani, etc., and is a 

 typical haunt of Glossina palpalis. (After Simpson.) 



Hodges distinguishes a natural range and a " following 

 range." By the former is meant the distance from water 

 within which the flies naturally wander in search of food, and 

 in most cases this natural range does not exceed 30 yards. 

 By following range is meant the distance to which flies will 

 follow victims who have passed through the natural range. 

 It rarely exceeds 300 yards, although flies have been caught at 

 distances of 1500 yards from any water. Native water carriers 

 are sometimes accompanied for long distances, the flies resting 



