100 



it may be in other ways, and moreover must have a certain amount 

 of good shade in proportion to its area. If there is good sliade near 

 water its absence elsewhere is immaterial. Vegetation that grows too 

 densely, as in the case of papyrus, is not associated with great numbers 

 of the fly. The percentage of females caught seems to indicate the 

 accessibihty of food supply, and probably variations in the amount of 

 blood available will influence the numbers of the adult fly, by affecting 

 the rate of reproduction. Shade produced by fresh green growth is 

 at once made use of by the fly for larviposition, hence pupae may be 

 locahsed according to the changing conditions of vegetation, while 

 they are readily killed by diminution of the shade. While breeding- 

 grounds are essential for maintaining a great abundance of fly, a certain 

 number can exist without locahsed breeding-grounds. It is therefore 

 obvious that clearing away vegetation from the breeding-grounds will 

 not wholly banish the fly. A Chalcid parasite, Syntomosj^hyrum 

 glossinae, has been reared from the pupae, but is very scarce. It is 

 thought probable that certain spiders have been responsible for con- 

 siderable diminution in the numbers of flies where conditions are 

 apparently favourable for their increase. ^ *^ 



Each island visited in the course of this tour is described. The 

 degree of infestation by Glossina palpalis and the factors influencing 

 it are discussed at length. It is obvious that clearing is an important 

 factor in control and that it must be very complete. Catching adult 

 flies destroys only a small proportion of females ; a method such as sticky 

 cloths on animals would be preferable in localities where males pre- 

 dominate in the catch. The extermination of large mammals would 

 have no effect upon G. palpalis which prefers reptilian blood, and the 

 destruction of all crocodiles and other large reptiles would be a difficult 

 matter. The author is of opinion that it is impracticable to infect the 

 fly artificially with any disease with the object of kilhng them off. 



Provided there is an area of good shelter as a base, flies may roam 

 along the shores, presumably in search of food and breeding-grounds, 

 in places where they could not reside owing to lack of shelter. 



The collection of pupae seems to offer the most promising results 

 owing to the proportion of the sexes being equal. It is therefore 

 suggested that all breeding-grounds should be cleared and that artificial 

 shelters should be provided that would induce the fly to deposit their 

 larvae in them ; from these the pupae could be collected regularly. 

 This method has been tried to some extent and the results undoubtedly 

 warrant further experiment. Such shelters should be in the form of a 

 low lean-to shed, the base and preferably the uprights being of metal, 

 owing to the presence of termites. The low front should face the 

 direction of the prevaihng wind ; the roof should be thatched with 

 good eaves, almost touching the ground in front ; the sides and back 

 should be open but protected by eaves and creepers. If the shelter 

 can be made of fresh, green growth this will add to its attractiveness, 

 and creepers might be planted to ramble over it. Diagrams and 

 photographs of such shelters are given. One of a suitable size has an 

 area of 12' X 4' and is 4|' high at the back and 1*' in front. 



It is obvious that constant attention must be given to such shelters 

 and the pupae regularly collected, otherwise they will tend to the 

 increase of the fly rather than to its diminution. The roofs must be 



