93 
only seen in transverse sections of the larva. The internal 
anatomy of the larva has not been accurately determined. 
e 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 
. m the specimen shown the present writer by Mr. Seddon 
these longitudinal ridges were plainly to be seen. Their 
presence, as will be sho later, is of importance in the 
identification of the larva. : 
1 rom the foregoing it will be seen that the worm is an 
immature Nematode, and that it closely resembles the sixth 
(1913) stage of Habronema muscae as described by Ransom 
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 
e 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. À 
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 
or Habronema. 
Since Carter first described the présence of a Nematode 
Worm in the head of a house-fly in 1861, many other workers 
— observed and a similar occurrence. 
t w 
tarvey Johnston (1912) recorded the finding = 
resembling that of Z. muscae in Stomozys calcitrans, and à 
Similar larva in Musca vetustissima. : " 
eo expressed the opinion that the larvae found y 
. Linstow and others in Stomozys calcitrans might possibly 
: m the larva of Habronema microstoma. 
