300 



THE INSECTS 



however, they may transmit disease directly, as with anthrax. Two species of 

 Chrysops have been found to transmit Filaria loa. 



Muscidae. 



The Muscidae, Sarcophagidae, and CEstridae are calyptrate Cyclorrhapha. 



The common housefly, M. domestica, is the best example of this family. 



The arista is feathered both dorsally and ventrally with straight hairs. The 

 fourth longitudinal vein bends down in a rather sharp angle as compared with 

 Stomoxys, which gives the first posterior cell rather a fusiform appearance. The eyes 

 are close together in the male, far apart in the female. The female lays about 125 



FIG. 84. Wing venation of A, Tabanus; B, Stomoxys; C, Glossina. 



eggs in a heap preferably in fermenting horse manure. The larva comes out in about 

 thirty-six hours. Very characteristic are the stigmata decorating the blunt posterior 

 ends. (See illustration.) 



The larval stage lasts seven to ten days and then the barrel- shaped pupal stage 

 is entered upon. This lasts about three days when the adult fly emerges. This 

 fly is incapable of biting, the piercing organs being fused with the labium, but may 

 transmit disease directly, carrying infectious material from the source, as in faeces, 

 to the food about to be ingested. Their r61e in typhoid fever is one of immense 

 importance. By reason of its hairy sticky legs, habits of frequent defecation and 

 constant regurgitation the housefly is an important agent in the spread of cholera, 

 dysentery, infantile diarrhoeas and tropical ophthalmias as well as typhoid. 



