DIPTERA. 



229 



Horse-flies or Hippohoscites. Larva apod and nearly 

 spherical, is nourished and attains perfection in the ovary 

 of its parent. Pupa changes in the same situation, and is 

 produced in the state in which it undergoes the final 

 change ; its structure is nearly as in the Musettes, excepting 

 an evident indentation at the end, which becomes the lower 

 extremity of the future imago. Imago with triarticulate 

 antenna, the second joint most developed, and the third 

 originating in a hollow or socket near the base of the se- 

 cond ; mouth apparently adapted for suction, its component 

 parts appear to be two mandibles, two maxilloi, and a 

 sheath-like labium; tarsi five-jointed; occasionally with 

 the fore wings developed, and the hind wings appearing as 

 poisers. Ornitliomyia, Stenepteryx and Oxypterum, which 

 live among the feathers of birds : Melophagus, the well- 

 known sheep-tick, fi-equents the wool of sheep : Hippo- 

 bosca, the horse-fly, runs over the softer uncovered parts of 

 the horse's skin, causing so intolerable an itching that 

 horses unaccustomed to the fly become perfectly ungovern- 

 able, and have often been known to throw their riders and 

 gallop headlong over fields or commons regardless of danger. 



