BACILLI AND TRYPANOSOMES IN THE FLY 41 



in 11 per cent, of the wild flies. Thus there is marked 

 incompatibility between the two. 



Since I have found bacilli in the gut of freshly hatched 

 flies, and even in pupae, their presence in the fly may have 

 something to do with the fact that only a few out of a 

 batch of flies fed upon an infective animal at the same 

 time will prove suitable hosts and will subsequently be 

 found to contain Trypanosomes. It may be that the 

 presence of bacilli in numbers is inimical to the Trypano- 

 some, or merely that they are present in flies which for 

 some other reason are physiologically unsuited to the 

 development in them of the Trypanosome. It would 

 be interesting to note the presence or absence of baciUi 

 in flies which contain T. vivax only in the proboscis. 



One of the points set me to be investigated was whether 

 palpalis can feed on anything except blood. I have not 

 been able to obtain any evidence that vegetable juices 

 are sucked up save that on Damba Isle I several times 

 found grains of banana starch in preparations made from 

 the gut of flies. I am inclined to think, however, that 

 this was accidental contamination of the preparation, 

 perhaps from a cloth used to wipe the slides, for it is 

 difficult to see how such material as banana could be 

 sucked up the narrow proboscis of Glossina. Small 

 fragments of vegetable tissue were sometimes met with 

 in preparations from the gut of a fly, but I am disposed 

 to think that they had been sucked up in water, for 

 pieces of alga were also found. 



Flies paid no attention to juicy papai fruit taken 

 down to the shore, although I have seen a mosquito 

 greedily feeding thereon. 



There seems more evidence that palpalis imbibes 

 water, but though they have often been seen sitting on 

 wet mud, no fly has ever been seen with its proboscis 

 lowered into the water. 



Examination of the contents of the gut of many 



