OP AGRICULTURE. 83 



about a half an inch in length. The body of the 

 female is black and marked witli' seven light-colored, 

 yellowish, narrow rings around it; the head is black, 

 and the eyes brown; the wings transparent, of a 

 rather yellowish tinge, veined, with black, and having 

 a distinct black mark on the outer margin of the 

 upper pair. The male presents much the same ap- 

 pearance as the female, but is more slender in form. 



The Smaller Ichneumon Fly. This ichneumon fly is 

 not quite the twentieth of an inch in length. The 

 head and throat black, and the legs and abdomen of 

 a yellowish color. Although it is so extremely small 

 as to be unobserved, it is constantly engaged in exter- 

 minating the cotton lice, myriads of which they 

 destroy by preying upon their vitals. The female fly 

 lays a single egg in the body of each louse, which, 

 when hatched, becomes a grub. This grub destroys 

 the interior substance of the louse, leaving only the 

 grey and bloated skin clinging to the leaf; then the 

 grub remains until it changes to a perfect fly, when 

 it emerges from a hole gnawed through the back, 

 and issues forth, furnished with four transparent 

 wings, to recommence the beneficial work of laying 

 more eggs in the colonies of lice on the neighboring 

 plants. The number of lice destroyed in this way 

 can be appreciated by observing the multitude of 

 empty skins, having a hole in the back through which 

 the fly escaped. 



The Syrphus. The young of the syrphus are found 

 wherever plant lice abound, and present the appear ^ 

 ance of small, yellowish, white, naked maggots, or 

 grubs, of about a fifth of an inch in length. Their 

 color is brown, with six distinct yellow spots on the 



