93 



only seen in transverse sections of the larva. The internal 

 anatomy of the larva has not been accurately determined. 

 The oesophagus is long, and the intestine occupies the main 

 part of the body cavity. 



The description of the larva as found by Lewis and 

 Seddon agrees closely with the above. They do not mention 

 the occurrence of fine longitudinal ridges in the cuticle, but 

 in the specimen shown the present writer by Mr. Seddon 

 these longitudinal ridges were plainly to be seen. Their 

 presence, as will be shown later, is of importance in the 

 identification of the larva. 



From the foregoing it will be seen that the worm is an 

 immature Nematode, and that it closely resembles the sixth 

 larval stage of Habronema muscae as described by Ransom 

 (1913). 



There is little or no direct evidence as to the mode of 

 entry of the larvae. As Habronema muscae was the only 

 species the life-history of which had been determined, it 

 became necessary to determine the life-histories and morph- 

 ology of the other two species of Habronema before it was 

 possible to attempt to identify the species of larva responsible 

 for the production of the lesions. 



Observations on the life-histories of the three species of 

 Habronema were therefore made, and these will be outlined 

 before the mode of entry and specific identification of the larva 

 are discussed. 



Obsrvations on the Life-histories of the Three Species 



of Habronema. 



Since Carter first described the presence of a Nematode 

 worm in the head of a house-fly in 1861, many other workers 

 have observed and recorded a similar occurrence. 



Ransom (1913) has shown that the embryos of Habronema 

 muscae are taken up by the larvae of Musca domestica, that 

 they develop through larval stages in the fly larvae and pupae, 

 and that the final larval stage of the worm is reached in the 

 adult fly, and is usually found situated in the head and 

 proboscis. 



Linstow, in 1875, described a Nematode larva in the head 

 of Stomoxys calcitrans which resembled the larvae found in 

 Musca domestica, but which he named Filaria stomoxeos. 

 Harvey Johnston (1912) recorded the finding of a larva 

 resembling that of H. muscae in Stomoxys calcitrans, and a 

 similar larva in Musca vetustissima. 



Ransom expressed the opinion that the larvae found by 

 Linstow and others in Stomoxys calcitrans might possibly 

 be the larva of Habronema microstoma. 



