81 



essential that the flies should be naturally fed." After a number of 

 unsatisfactory attempts with other sources of blood, the experimenter 

 in every case permitted the flies to feed on his own fingers. 



Feeding. On this subject the author writes : " The attitude 

 during feeding is of course well known, the fly standing firmly on all 

 six feet and thrusting its honey-brown proboscis vertically downwards 

 into the skin, whilst the ensheathing palpi project forwards and 

 upwards. As pointed out by Dr. Moiser, the fly sometimes partly 

 withdraws its proboscis and thrusts it in again and again, but once a 

 satisfactory well of blood has been tapped, the abdomen fills rapidly, 

 and in from one to two minutes the act of feeding terminates and the 

 fly, withdrawing its proboscis, moves to one side and presently flies 

 heavily away. 



ig. 6. A Tsetse-fly (Glossina morsitans, Westw., O), before feeding. 



" In my 'experiments I have usually found the bite painless. Some- 



i ! times, however, it was decidedly painful, and I can only account for 



| this by supposing that on these occasions the proboscis entered 



I sufficiently near to one of the sensory spots of the skin to stimulate it. 



On the other hand there was generally some degree of smarting at the 



site of puncture after the feed was over, and it is probably this which 



usually attracts the attention of the victim to the presence of the fly, 



which having already fed is able to escape on the first indications of 



uneasiness. 



Fig. 7. A Tsetse-fly (Glossina morsitans, Westw., $), after feeding, showing 

 abdomen distended with blood. ( x 6.) From a drawing from life by Lady Brace, 

 R.R.C. (Both the above figures reproduced, by permission of the Trustees 

 of the British Museum, from " A Handbook of the Tsetse-Flies [Genus Glossina]," 

 by E. E. Austen. London : British Museum (Natural History) . 1911.) 



" If undisturbed, the fly feeds until the abdomen is relatively greatly 

 distended and of a bright red colour, due to the blood showing through 

 the tense and semi-transparent tissues. The dorsal plates of the 

 abdomen are widely separated, so that the body loses its characteristic 

 dark colour. The appearance is therefore somewhat different from 



(5979) F 



