TWO-\VIx\GED INSECTS. 



169 



downward, and with the hind extremity of the body — 

 through which they breathe — at the surface of the 

 water. At length they shed their skins and enter 

 upon the pupa state, in which tliey live at the surface 



Fig. 287. — Horsefly. 



Fig. 288. — Bee Fly. 



55=^ 



Asilus Fly. 



Fig. 290. — Horse Botfly. 



of the water, and breathe through two tubes on the 

 thorax. In a few days the skin splits on the back, the 

 winged insect appears, and, after resting awhile on its 

 empty skin as it floats upon the water, spreads its 

 wings, and, flies away in search of a victim. 



Hessian Fly and Wheat Fly. 



The Hessian Fly expands about one fourth of an 

 inch, and has the head, antenna;, and thorax black, 

 the wings blackish and fringed with short hairs. The 

 hind body is tawny, with black on each ring; the legs 

 are brownish, and feet black. Two broods appear in a 



