DISEASES OF THE COTTON PLAOT. 
233 
The Smaller Ichneumon Fly. — {Ichneumon?) 
The iclmeumon fly wMcli destroys tte aphis, or louse, 
so very injurious to the cotton plant, is a minute insect, 
not quite the twentieth of an inch in length. The head 
and thorax are black, and the legs and abdomen of a yel- 
lowish color. Although so extremely small as to be un- 
observed, it is constantly engaged in exterminating the 
cotton lice, myriads of which it destroys 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 devours the interior substance of the aphis, leaving 
only the gray and bloated skin clinging to the leaf. This 
skin serves the young larva for a shelter, where it remains 
until it changes into the perfect fly, when it emerges from 
a hole gnawed through the back, and issues forth famished 
with four transparent wings, to recommence the beneficial 
labor of depositing more eggs in the surrounding colonies 
of lice on the neighboring plants. 
The number of lice destroyed in this way can be more 
fiilly appreciated by observing the multitude of empty gray 
and bloated skins, more or less scattered over the cotton 
plants infested, each skin having a hole in the back through 
which the perfect fly has escaped. 
The Syrphfs. 
The laiTse of this syrphus are found wherever aphides, 
or plant-lice abound, and present the appearance of small, 
yellowish-white, naked maggots, or grubs, of about a flfth 
of an inch in length. Their color is brown, with six dis- 
tinct yellow spots on the first three segments of the body, 
and the sides are also marked on the margin with yellow ; 
