THE BOT FLY. 79 



excrement. The pupa state lasts for thirty or forty days, and 

 the perfect fly appears the next season, from June until October. 



The Bot fly of the ox (Hypoderma bovis, Fig. 81, and lar- 

 va), is black and densely hairy, and the thorax is banded with 

 yellow and white. The larva is found during the month of May, 

 and also in summer, living in tumors on the backs of cattle. 

 When fully grown, which is generally in Jul}', they make their 

 way out and fall to the ground, and live in the pupa-case from 

 twenty-six to thirty days, the fly appearing from May until Sep- 

 tember. It is found all over the world. The OEstrus ovis, or 

 sheep Bot fly (Fig. 82, larva), is of a dirty ash color. The 

 abdomen is marbled with yellowish and white flecks, and is 

 hairy at the end. This species of Bot fly is larviparous, i. e., 

 the eggs are hatched within the body of the mother, the larvje 

 being produced alive. M. F. Brauer, of Vienna, the author of 

 the most thorough work we have on these flies, tells me that he 

 knows of but one other Bot fly (a species of Cephanomyia) 

 which produces living larvse instead of eggs. The eggs of cer- 

 tain other species of Bot flies do not hatch until three or four 

 days after they are laid. The larvas of the sheep Bot fly live, 

 during April, May and June, in the frontal sinus of the sheep, 

 and also in the nasal cavity, whence they fall to the ground 

 when fully grown. In twenty-four hours they change to pupae, 

 and the flies appear during the summer. 



We also figure the Cuterebra buccata (Fig. 83 ; a, side view,) 

 which resembles in the larval state the ox Bot fly. Its habits 

 are not kuo^N-n, though the j'oung of other species infest the 

 opossum, squirrel, hare, etc., living in subcutaneous tumors. 



The banded Lithacodes, 



