252 GLOSSINA AND DISEASE [CH. 



From this point of view it is worthy of notice that, in spite 

 of numerous experiments, up to the present no one has suc- 

 ceeded in transmitting T. gambiense by G. palpalis or any 

 other tsetse-fly on the west side of Africa. It seems that 

 the West African races of G. palpalis, are more or less refractory 

 to infection with T. gambiense, for the climatic conditions in 

 Dahomey, Casamance and in Uganda, do not differ sufficiently 

 to explain the difficulty of transmission in the two former 

 districts. 



Thus the evolution of trypanosomes in the invertebrate 

 host is a very complex problem and, before commencing pro- 

 phylactic measures in any particular district, it is first of all 

 necessary to determine, by careful experiments with the local 

 races of Glossina, which species are responsible for the spread 

 of the local strains of trypanosomiasis. If this is not done, 

 there is a great danger of administrative efforts being wasted in 

 the attempt to destroy a comparatively harmless species of 

 Glossina, whilst the more important carrier escapes. The results 

 of experiments in other neighbourhoods are of very little use, 

 for, as mentioned above, in one district T. cazalboui is carried 

 by G. palpalis, whereas in another all attempts to infect this 

 tsetse with the same trypanosome have been unsuccessful. 



In the following pages we have summarized the available 

 information concerning the bionomics of all species of Glossina 

 that have been proved to carry any infection, together with a 

 brief mention of the infections they are known to transmit. 

 Further details of the experiments and observations on the 

 latter point will be found under the heading of the various 

 species of trypanosomes (Chapter XVIII). 



REFERENCES. 



Austen, E. (1911). Handbook of the Tsetse-Flies. British Museum, 



(Nat. Hist.) London. 

 Newstead, R. (1911). Bull. Ent. Research, vol. n. p. 9. 



(1912). Ann. Trop. Med. and Parasit., vol. vi. p. 129. 



