42 



The Food of G. morsitans. 



contained nucleated blood. From measurements, it seems highly probable 

 that in all three cases the blood was avian, not reptilian. The average 

 length of corpuscles and nuclei of blood from several different reptiles 

 was measured and found to be — corpuscles 15 microns, nucleus 5"9 microns ; 

 while the blood of several different birds gave as the average — corpuscles 

 11 - 8 microns, nucleus 4*6 microns. In the three cases under consideration 

 the average of the corpuscles was 10 - 5, 10 - 0, and 1O0 microns respectively, 

 and that of the nuclei 4*7, 4 - 8, and 4*4 microns. Probably the size of 

 the nucleus is the better guide than that of the whole corpuscle, as being less 

 altered by digestion. 



In no case was vegetable matter noted in the intestinal contents. 



Trypanosomes were found in 14 flies — 2-8 per cent. — but many of the 

 smears were so thick and so much obscured by the fat-body and other 

 structures of the fly, that probably trypanosomes were present in other 

 cases. 



Of the 30 female flies examined, 13, or 43*3 per cent., contained mammalian 

 blood, and there was nothing to suggest that they differed in their feeding 

 habits from the males. 



From experiments with flies in the laboratory, it was found that blood is 

 recognisable in stained specimens for two to three days after a feed, but not 

 beyond the third day. Hence it may be inferred that, roughly, half the 

 flies examined had fed within, at most, three days of their capture, and 

 that therefore the flies feed naturally at least once every six days. 



Conclusions. 



1. The food of Glossina morsitans consists mainly of mammalian blood 

 (99 per cent.), chiefly from species of antelope, and what appeared to be avian 

 blood (1 per cent.). 



2. There is no difference in the feeding habits of males and females. 



3. Probably the flies feed once in five or six days. 



