83 



turbid, but the succeeding drops are of clear water-like fluid and are of 

 the size of a pin's head. For about twenty minutes they are exuded at 

 intervals varying from 15 to 75 seconds, the intervals being somewhat 

 longer towards the end of this period. Thereafter no more drops are 

 ejected for several hours, and those that follow are of a thick chocolate 

 brown excrement .... Coincident with the extrusion of these 

 drops, which are presumably the fluid constituents of the blood, there 

 is a marked shrinking in the size of the abdomen. 



" Soon after digestion has begun the appearance of the blood in the 

 distended abdomen of the fly begins to change. Commencing at the 

 distal end and spreading upwards the abdomen loses its bright red 

 colour and gradually darkens, so that in from twenty minutes to half an 

 hour the last tint of red has gone. The last part to darken is a narrow 

 zone around the gaseous bubble, and as has been suggested above, this 

 may be due to the presence of free oxygen in it. 



" Slight differences were observed in the case of the female G. 



palpalis. When fully distended with blood her abdomen appeared to 



1 be deeper, or less dilated laterally, than in the case of the male, and 



i the process of darkening of the ingested blood was considerably more 



rapid. In one case the last trace of red colour had disappeared from 



the abdomen in ten minutes." 



As regards the feeding of Glossina morsitans, Dr. Allan Kinghorn, 

 of the Luangwa Sleeping Sickness Commission, Northern Rhodesia, 

 | wrote (79) in August 1911 : " The method observed in preserving and 

 feeding the captive flies was essentially that described by Kleine. 



" Freshly caught flies, two females and one male, were placed in 



i wide-mouthed glass tubes, measuring 5 by 2 in., and the mouth was 



I then closed over with mosquito-netting held on by an elastic band. 



i The flies were fed daily on native fowls during the warmer hours of 



i the day, when they readily gorged themselves. Roubaud has recorded, 



i in the case of Glossina palpalis, that the females do not feed as often 



as the males, but this has not been found to be so with G. morsitans. 



Both sexes have fed with equal avidity. After the completed meal 



j the insects were changed into clean, unlined tubes, and under these 



i conditions it has been possible to keep some of them alive for over 



two months, at the time of writing, and to obtain larvae. 



" When first introduced into the tubes the flies are very active, 



making wild efforts to escape, but in a very short time they become 



habituated to their new surroundings and remain quiescent. The 



males have been found to die much sooner than the females, and this 



may possibly indicate that the natural duration of their life is shorter." 



Mr. LI. Lloyd, Entomologist to the Luangwa Sleeping Sickness 



; Commission, wrote (88) in the following year : " Owing to the difn- 



! culty of obtaining suitable mammals, native fowls were used almost 



i entirely as blood donors for the captive flies. The small numbers of 



pupae obtained would seem to indicate that fowls' blood is not a very 



; suitable food. This is perhaps because the blood forms large firm 



clots in the sucking stomachs of many of the flies. When the blood 



has attained this condition it cannot apparently be utilised by the 



flies, as the clots persist for some weeks after the meal on fowls, though 



monkeys may have been used as food in the interim. When such a 



clot is formed it would be impossible for the fly to retain a full-grown 



larva in the uterus. The phenomenon has not been observed with 



mammals' blood, nor has it been observed in nature. 



" No evidence has been obtained that the flies take any food other 

 than blood. Out of 67 freshly caught flies that were dissected, 



