BY T. HARVEY JOHNSTON AND M. J. BANCROFT. 75 



grew to full size and pupated. Twentj^-eight of the resulting 

 flies Avere examined, two of them proving to be infected 

 with Habronema. In one fly one worm occurred, in the 

 other, tAvo worms. In both cases the parasites were too 

 small to be specifically identified. It is not known whether 

 Habronema larvae can develop fully in this fly. Probably 

 certain other blowflies could be similarly infected. 



VII. — Sarcophaga misera Walker. This fly has been 

 found breeding naturally in horse dung, though it is usually 

 a carrion feeder in the larval stage. Three larvae taken 

 from horse dung were examined, and a minute Habronema 

 found in each. Twenty-five flies bred from the same 

 material were subsequently examined, eleven of them 

 being found to contain Habronema. The number of worms 

 found ranged from one to eight, both H miiscce and H. 

 megastoma being present in several flies. 



VIII. — -Fannin sp. A small black species of Fannia 

 (Anthomyidse) commonly associated with cattle, has been 

 found breeding naturally only in cow dung, and an attempt 

 to induce it to breed in horse dung failed, the young larvae 

 being killed by a growth of mould. It is quite probable 

 that, under favourable circumstances, Fannia larvae would 

 mature in horse dung, but whether Habronema could 

 develop in this fly is only a matter of conjecture. 



Heavier infection of native species of Musca than of 

 M. dornestica. 

 For some time it has been observed that when flies 

 belonging to either of the common native species of Musca 

 wore bred on dung from a certain horse, the resulting 

 infection was far heavier than when house flies were reared 

 from material from the same source. Thus, during May 

 and June, 1919, a number of heavily infected M. fergusoni 

 pupae bred on dung of horse " iS "' were examined and 

 actual count of the worms in one gave 91, whilst during 

 June a number of house flies bred on material from the 

 same horse were examined, the average infection being 16 

 with a maximum of 41 — less than half the number counted 

 in a pupa of 21. fergusoni taken at random. To test this 

 observation more thoroughly, a number of eggs of 

 M. dornestica and M. vetustissima, laid on the same day, 



