BY T. HARVEY JOHNSTON AND M. J. BANCKOFT. ."JT 



vigilax, Chrysoconoihs acer, Culex sitiens, Pseudoskusea 

 basalis and Tceniorhyiichus uniformis (1917). 



Result of efforts to infect M. fergusoni, M. vetuslissimaf 



M. terroe-reginoe and the small black Fannia with 



Onchocerca gib-soni. 



The method followed was to allow the caged flies to 



suck the juices from a freshly cut live worm nodule obtained 



as soon as possible after the slaughter of the bullock. 



The above species of flies which fed very eagerly on 

 nodules were killed at varying intervals for dissection. 

 In the case of M. fergusoni and M. vetustissima it was 

 noticed that only a few flies out of each batch actually 

 ingested the embryos in any quantity. Dead embryos 

 were found in an undigested state in flies up to the Gth 

 day after feeding. Living embryos were once found in a 

 fly one day after feeding. In the case of the small black 

 Fannia, on the other hand, embryos were ingested by the 

 majority of flies in one batch experimented with, many 

 remaining undigested, chiefly in the crop, for as long as 

 14 days after feeding. On another occasion undigested 

 embryos were found in a fly of th's species 16 days after 

 feeding. In all cases, however, the embryos were dead 

 In no case was there any suggestion of development of the 

 Onchocerca embryos withiji the fly, and, as far as these 

 experiments go, they do not indicate any of the above 

 flies as carriers of the parasite. It must be remembered^ 

 however, that the method of allowing flies to feed on an 

 opened nodule is totally unnatural, since the majority of 

 the embryos obtained in this way are liberated from the 

 uterus of the female by the act of cutting and may not be 

 in a fit state to commence development in the intermediate 

 host. In nature the embryos in their passage from the 

 parent to the exterior — however this may be accompiiished 

 — may become, as it were, strengthened and fitted to begin 

 their cycle in the invertebrate host. 



Our results are given for convenience in tabular form. 

 The number of flies dissected out of each batch, whether 

 captured or bred in the laboratory, and the number of days 

 which were allowed to elapse before dissection are indicated. 

 Other parasites present are noted under " Remarks." 



