CECIDOMYID^E. 11 



these is Cecidomyia (Olifjotrophus) destructor, commonly call- 

 ed the Hessian Fly, from the belief, probably erroneous, that 

 it was first introduced into this country in straw brought 

 by Hessian troops during the Revolution. 



The fly is very small, but little more than an eighth of an 

 inch in length, of a prevailing black color, with the abdomen 

 pinkish or brownish. There are two broods, in spring and 

 autumn. The female deposits her eggs, one or two at a time, 

 on the upper side of the leaves of wheat, to the number of 

 from eighty to a hundred, or even more. Hatching in from 

 four to eight days, if the weather is favorable, the yellowish 

 red larvae crawl downward on the leaves until they insert 

 themselves between the leaf and the stalk. Here they remain 

 quiescent, growing by means of imbibition or absorption of 

 the juices of the plant, until they reach the size of a small 

 grain of rice. The larvae that are hatched in April in a few 

 weeks assume the pupa state, called the flax-seed stage. In 

 August the second brood appears, the female of which deposits 

 her eggs in young winter wheat or other grain, where the lar- 

 vae soon hatch and acquire the flax-seed condition in a few 

 weeks, or by November, in which condition they pass the 

 winter. In England there is but one brood, that of early 

 summer, and the fly is not nearly so injurious to growing grain. 



TABLE OF GENERA. 



Fourth longitudinal vein wanting. . , . CECIDOMYIN^:. 



Fourth longitudinal vein present. . . . . LESTREMIIN^K. 



CECIDOMYIN^E. 



1. Fifth longitudinal vein furcate, the first joint of the tarsi usually shorter 



than the following . 2 



Fifth longitudinal vein not furcate, the metatarsi longer than the follow- 

 ing joint, the last two joints very small. ... . . 14 



2. First and third longitudinal veins distinctly separated from each other 



and from the costa ; costa not tomentose. . ... 3 



First and third veins closely 'approximated to the costa and difficult to 



distinguish, the costa apparently thickened. . . . . 12 



