72 THE HOUSE FLY DISEASE CARRIER 



also been given the specific name Mnsca domestic^ by 

 H. Werner. 



NEMATODE PARASITES OF THE TYPHOID FLY 



The nematodes, or thread-worms, have long been 

 subjects of observation. They are greatly elongated, 

 thread-like organisms, frequently of considerable size ; 

 for the most part laying eggs, but in rare cases bearing 

 living young. The younger stages or larvae of most 

 of them have a different habitat from that of the adult 

 worm. Some of them develop in damp, muddy earth, 

 migrating finally to lead a parasitic life within some 

 animal ; some are parasitic in plants. The old time super- 

 stition that a horse-hair when left in water for a suffi- 

 cient length of time becomes a living worm arises from 

 observations upon some of the largest nematodes. Very 

 many insects are parasitized by the worms of this group. 



H. J. Carter, in Bombay, in November, 1859, while 

 examining the head of a common house fly, noticed 

 that two nematode worms came out of it. Later, in 

 July, 1860, he discovered that on the average about 

 every third fly in Bombay contained from two to 

 twenty or more of these worms, which were chiefly 

 to be found in the proboscis, though occasionally oc- 

 curring among the soft tissues of the head and hinder 

 part of the abdomen. He described them as bisexual, 

 mature, and nearly all of the same size. He placed 

 them in the genus Filaria, and described them as Filaria 

 muscc? in the Annals and Magazine of Natural History, 

 Vol. VII, pages 30-31. 



