85 



produced in the laboratory." Elsewhere, Mr. Lloyd says : " On the 

 average the pupae produced on mammalian blood are larger than those 

 bred on avian blood. This advantage is 4 per cent, in length and 

 5 per cent, in breadth .... 



" In the avian series there was a large proportion of very small 

 pupae. Of these 22 (36 per cent.) measured 5 5 mm., or less, in length, 

 while in the mammalian series 11 (13 per cent.) only were of these 

 dimensions. The avian series, however, also included a few pupae 

 which were equal in size to the largest bred on mammals' blood. 



" The small size of these pupae is considered to be due to the pressure 

 of the clots of blood which form in the sucking stomachs of some of the 

 flies when fed on avian blood." 



A tendency to overfeeding on the part of the captive flies was 

 observed in the course of these experiments. " On three occasions," 

 writes Mr. Lloyd, " they have been known to feed till an internal 

 rupture of the gut was caused." 



Passing on to consider the relation of G. morsitans to the smaller 

 animals, the author remarks with reference to the foregoing series of 

 investigations : " These experiments point to the conclusion that the 

 advantages of a mammalian diet as opposed to an avian one are not 

 great and are due to the fact that mammalian blood is more easily 



digested than avian While the fly is apparently unable 



to carry on its species on a reptilian diet, occasional meals of such blood 

 would assist the individual in prolonging life." As to this, Dr. 

 G. A. K. Marshall writes in a footnote : " Mr. F. W. Fiske has already 

 pointed out (Bull. Ent. Res., iv., p. 103) that the results of laboratory 

 experiments upon the food value of reptilian blood should be accepted 

 with some reserve, as they are not borne out by field observations. 

 Dr. H. L. Duke and Dr. G. D. H. Carpenter have noted that G. palpalis 

 feeds freely on monitor lizards, under natural conditions on the islands 

 in Lake Victoria, and as a result of his own recent observations in the 

 same locality Mr. Fiske concludes that these lizards constitute the 

 most favoured food of that fly." 



STUDY OF THE NATURAL FOOD OF TSETSE-FLIES, BY EXAMINATION 

 OF THE CONTENTS OF THE ALIMENTARY CANAL. A better method of 

 determining the normal food of Tsetse-flies consists in the examination 

 of the intestinal contents of flies caught under various conditions of 

 environment. We give below a resume of some of the investigations 

 that have been made in this direction upon G. palpalis and G. morsitans. 



The Proceedings of the Royal Society of London, Series B., 

 Vol. LXXXIL, 1910, contain a series of important reports on the work 

 of the Sleeping Sickness Commission of the Royal Society, in Uganda, 

 1908-10, by Colonel (now Major-General) Sir David Bruce, C.B., 

 F.R.S., A. M.S., Captain (now Lieut. -Colonel) A. E. Hamerton, D.S.O., 

 R.A.M.C., Captain H. R. Bateman, R.A.M.C., and Captain F. P. Mackie, 

 I. M.S. Writing on " The Natural Food of Glossina palpalis," the 

 authors state : " In the laboratory it was found that the flies fed 

 with far more avidity on birds than on monkeys, while they could 

 hardly be tempted to feed on young crocodiles, iguanas [monitors], 

 or lizards." The microscopical examination of the intestinal contents 

 of 403 captured flies, however, yielded the following results. 



Of 220 G. palpalis, " caught at various parts of the Lake-shore," 

 and dissected for the most part " during October, November and 

 December, 1908," generally about 24 hours after capture, 27-3 per 

 cent, contained blood in the intestine. As regards character of the 



