74 THE HOUSE FLY—DISEASE CARRIER 
“Twenty-six dipterous larvae (species not deter¬ 
mined) from horse manure which were examined for 
the presence of nematodes were all free from infection 
with H. musca;. Thirteen larvae of Musca domestica 
and several pupae were examined with negative results. 
These were bred from house flies confined in a dish 
with horse manure which had previously been boiled 
to destroy any fly larvae or nematodes which might 
have been present. That some of the flies were infested 
with Habronema was determined by examining a num¬ 
ber after oviposition had occurred. An undersized 
male which developed in the culture just referred to, 
the only adult that was obtained in this culture, was 
examined with negative results. 
“That infection with Habronema muscce is acquired 
during some stage prior to the imago was proved by 
the discovery of the parasites in a fly caught just as it 
was emerging from the pupa (No. 9, referred to 
above). Beyond this fact the observations made by 
me (made incidentally in the course of another in¬ 
vestigation) have proved little as to the life history of 
the parasite. On several occasions I have placed the 
worms taken from flies in water and in horse manure, 
but in no case was it observed that any further develop¬ 
ment occurred. The worms invariably died within a 
few days. It would seem, however, that the larval 
stage of the parasite which is found in the fly must in 
some way escape from its host, reach sexual maturity 
either as a free living form or in another host, and 
produce young which find their way into other flies 
