Insects . and Parasitic Diseases. 33 



31; Xo. 11, page 31; No. 12, page 31; No. 13, page 32; No. 14, 

 page 32. 



In the first of these experiments (No. 10), 47.7% of the flies 

 examined were infected, and in the remaining four 100% of those 

 examined harboured from a few to 60 parasites each. In most 

 cases the majority of the parasites were located in the proboscis and 

 head, particularly in heavily infected individuals. The following 

 record of the location of parsites is fairly typical : — Fly (a) har- 

 boured 45 parasites, of which 10 were located in the proboscis, 20 

 in the head, and 15 in the thorax and abdomen ; fly (b) harboured 

 36 parasites, of Avhich 15 were found in the proboscis and 21 in the 

 head; fly (c) harboured 27 parasites, of which 12 were in the pro- 

 boscis, 14 in the head, and 1 in the thorax; fly (d) harboured 30 

 parasites, of which 15 were in the proboscis and head, and 15 in 

 the thorax and abdomen ; fly (e) harboured 60 parasites, of which 

 35 were found in the proboscis and head and 25 in the thorax and 

 abdomen. 



Encysted larvae are frequently found in the abdomen of the 

 infected fly. Generally a cyst contains a single larva, and there 

 may be several cysts in one fly. Larger cysts containing more 

 than one parasite are seldom found. One Stomoxys fly, however, 

 which Avas found to harbour over 60 parasites, contained three 

 cysts in the abdomen, one of which enclosed one parasite, one five 

 parasites, and one seven parasites. 



C. To determine the viability of embryonic Habronema micros- 

 toma in faeces. 



It has been shown (Experiment No. 10, p. 31, that embryonic H. 

 microstoma may survive for a period of fifteen days in sterilized 

 faeces and still remain capable of infecting fly larvae. In this 

 experiment embryos were incubated in faeces from December 3rd to 

 December 18th, before being exposed to ingestion by Stomoxys 

 larvae. All embryos found on the latter date were enclosed in 

 sheaths. The resulting flies were examined between January 7th and 

 10th, wheji over 47% were found to haibour from one to three para- 

 sites each. 



Under favourable natural conditions the period of viability is 

 possibly quite as long — indeed there is some reason to believe that 

 a fairly long period of viability in faeces is necessary for the 

 propagation of the species. This aspect of the life-history of H. 

 n^icrostoma is referred to more fully elsewliere in this report. (See 

 page 44). 



