THE STABLE-FLY 131 



air into its body, forces it along the tracheae in 

 the wings, which expand and ultimately harden. 

 In the processes of unfolding they are aided 

 by the hind legs. For a time the insect is 

 immobile, gradually stiffening; but when the 

 integument has hardened it flies off to explore 

 the outer world. Under normal conditions 

 the whole life-cycle varies from 

 twenty-seven to thirty-seven 

 days. 



The chief interest of Stomoxys 

 to the public, rests upon the fact 

 that it is a very potent carrier 

 of disease. There are certain 

 forms of Trypanosoma which, 

 under experimental conditions, ^ ^^- *^~~ 



••• Uoarctate pupa 



are undoubtedly transferred by of stomoxys cai- 

 this species. But opinion is still ^ewstead ) ^^^^'"'^ 

 unsettled as to whether the trans- 

 ference of these protozoa occurs in nature. The 

 Surra diseases of horses and camels is, according 

 to some authorities, transferred by Stomoxys, 

 and so is the Surra disease of cattle ; and 

 there are others, all fully set forth in Mr. 

 Hindle's work on * Flies and Disease.' 



Certain thread-worms — for instance, Filaria 

 labiato-papillosa — which occur in the peri- 

 toneal cavity, and sometimes in the eyes 

 of cattle and deer in India, are undoubtedly 

 conveyed by Stomoxys calcitrans. The super- 



K 2 



