520 ftATU&ALIST's CABINET 1 . 



Ox gad fly. 



The ox gad-fly has brown unspotted wings; 

 and the abdomen is marked with a black band 

 in the middle., and has dusky yellow hairs at the 

 tip. The front is white, and covered with down ; 

 and the thorax is yellowish before, black in the 

 middle, and cinereous behind. The female dif- 

 fers from the male, in having a black style at the 

 end of the abdomen. 



This insect deposits its eggs in the back of the 

 ox; and the larva lives beneath the skin, be- 

 tween this and the cellular membrane. Its sac 

 or abscess is somewhat larger than the insect, 

 and, by narrowing upwards, it opens externally 

 to the air by a small aperture. 



When young, the larva is smooth, white, and 

 transparent, but, when full grown, is of a deep 

 brown. It is also supplied in this state with in- 

 numerable minute hooks, ranged in contrary di- 

 rections on its body ; with which, by occasion- 

 ally erecting or depressing them, it is moved 

 about in the abscess ; and from this motion, and 

 the consequent irritation, a more or less copious 

 secretion of pus takes place for its sustenance^ 

 As soon as the larva is full grown, it effects its 

 escape from the abscess by pressing against the 

 external opening. When this becomes of suffi- 

 cient size, it writhes itself through, and falls from 

 the back of the animal to the ground; arid, seek* 

 ing a convenient retreat, becomes a chrysalis. 

 After the exit of the larva, the wound in the skin, 

 is generally closed up and healed in a few days., 

 3 



