XX] TRYPANOSOMIASIS 363 



cases the first animal became infected whilst the second did 

 not ; but in the third experiment, in which only a single Stomo- 

 xys was used, both animals became infected after one bite. In 

 addition positive results were obtained in the transmission of 

 this virus after intervals varying up to at least three days. As 

 Dr Bagshawe remarks, these experiments demonstrate that the 

 trypanosomes of the Surra type in French West Africa may 

 be transmitted by Stomoxys and that the flies may retain the 

 infection for at least three days. But it is so obvious that 

 some of the flies may have been infected when caught, that 

 definite conclusions as to the period during which Stomoxys 

 retains infection, may be as misleading as were those drawn 

 from similar experiments with G. palpalis. 



Nevertheless, the fact that a single Stomoxys was capable of 

 transmitting the infection shews that under certain conditions 

 this insect might be an important agent for the spread of the 

 disease. By means of interrupted feeding, that is, the fly 

 beginning its meal on an infected animal and at once finishing 

 it on another, various authors have succeeded in the experi- 

 mental transmission of T. brucei, T. gambiense, T. equiperdum, 

 in addition to T. evansi, T. cazalboui and T. soudanense. 



In India, Leese is of the opinion that Surra (T. evansi) 

 may be naturally spread by the bites of Stomoxys, but the 

 results of experiments shew that Tabanus is a much more 

 efficient carrier as far as direct transmission is concerned 

 (vide p. 237). In Mauritius, where Stomoxys nigra Macq. is 

 very abundant, this species is believed to be concerned in the 

 spread of the same disease, but experimental evidence is lacking. 

 Finally it should be noted that in practically all experiments 

 with Stomoxys in Africa, no distinction has been made between 

 5. calcitrant and 5. nigra both species being used indiscrimi- 

 nately. 



REFERENCES. 



Austen, E. (1909). African Blood-sucking Flies. 



Bagshawe, A. G. (1912). 5. 5. Bulletin, vol. iv. p. 273. 



Bevan, LI. (1910). Ibid. vol. n. p. 252. 



Bouet and Roubaud (1912). Bull. Soc. Path. Exot. vol. v. p. 544. 



Bouffard (1907). Compt. Rend. Soc. Biol vol. LXII. p. 71. 



