Insects and Parasitic Diseases. 15 



require to be fed during their captivity, and larvae of the first 

 _generation only weie reared, and used in all the experiments with 

 this species, owing to pressure of time when these flies and the 

 Helminth material were obtainable. 



A. — Habronema muscae, Carter. 



1.— Historical. 



A full account of tlie life-history of Habronema muscae, Carter, 

 known since 1861 as a parasite of the House-fly (Musca domestica), 

 ^vas published by Dr. B. H. Ransom in 1913. As a result of his 

 investigations it was shown that the life-history of this nematode 

 is one requiring for its completion a simple alternation between 

 two hosts, a vertebrate harbouring the adult parasite and; an inver- 

 tebrate harbouring the larval stage. 



From horse faeces collected in the streets of Colorado Springs, 

 U.S.A., on August 9th, 1911, Ransom bred flies (M. domestica) 

 from which in the larval, pupal, and adult stages, he obtained a 

 series of nematode larvae in successive stages of development com- 

 mencing with a stage measuring about 0.4 mm. in length, from a 

 fly larva, and reaching a maximum length of 3.2 mm,, in an adult 

 fly. On September 11th, 1911, he found amongst numerous filarioid 

 Avorms collected from the stomach of a horse, larval worms in the 

 «ame stage of development as those from flies. The adult worms 

 from the liorse's stomach were all of one species, and the younger 

 stages formed a series between tlie adults on one hand and the 

 larval Habronema muscae from flies on tlie other, thus establish- 

 ing the fact that Habronema muscae of the fly, Musca domestica, 

 is the larval stage of a parasite, the adult stage of which occurs in 

 the stomach of the horse. 



This parasite was shown to be similar to, but distinctly dif- 

 ferent from, a species found in the stomach of the horse, and 

 known since 1886 as Spiroptera microstoma (Schneider), now cor- 

 rectly designated Habronema microstoma (Schneider). 



In a further account of the development of the larvae of Habro- 

 nema muscae within the body of the fly, Ransom gives details and 

 drawings of six definite stages through which the parasites pass 

 before reaching the stomach of the definitive host, to which stages 

 reference will be made later on. 



Seurat (1916, p. 321) considers that Ransom is quite wrong in 

 describing these different steps in the development of the larval 

 Habronema muscae within the fly (pupa and adults), as true stages. 



