820 
ANNUAL REPORT OF NEW YORK 
HESSIAN FLY. ITS TRANSFORMATIONS. 
attract general notice in that neighborhood, until 1779. Prom 
thence as a central point, it gradually extended over the country 
in all directions, advancing at the rate of from ten to twenty 
miles a year. Most of the wheat fields were wholly destroyed by 
it within a year or two of its first arrival at a given place, and 
its depredations commonly continued for several years, when 
they would nearly or quite cease— its parasitic insect enemies 
probably increasing to such an extent as to almost exterminate 
it. It is occasionally reappearing in excessive numbers in one 
part and another of our country. We hear of it at the present 
time as verv destructive in Illinois and some of the contiguous 
States, the crop in many wheat fields being totally ruined by it. 
This insect, as a general rule, passes through two generations 
annually. The first of these occupies the autumn, winter and 
fore part of spring, and is reared at the roots of the young grain, 
slightly under the surface of the ground. The second occupies 
the remainder of the spring and the summer, and is nurtured in 
the lower joints of the straw. The time when its several changes 
occur, however, is not perfectly uniform, being varied by the 
climate, the state of the weather, and perhaps other contingen¬ 
cies ; and it is not improbable that individual specimens, placed 
in circumstances unfavorable to their development, in some 
instances have their growth so much retarded as to require even 
a whole year to complete their metamorphoses. 
In the ordinary course of nature, therefore, our crops of win¬ 
ter wheat are liable to two attacks of the Hessian fly, one gen¬ 
eration reared at its roots producing another which occupies the 
lower joints of the stalks. Thus the larvae and pupae are present 
in it almost continually, from the time the tender young blades 
appear above the ground in autumn till the grain ripens and is 
harvested the next summer. Our spring wheat, on the other 
hand, can rear but one brood of these insects ; they consequently 
resort to it but little if at all. Nor can the Hessian fly sustain 
itself, except in districts where winter wheat is cultivated, in 
which for it to nestle during the autumn and winter. 
The eggs of the first generation, or that which is nurtured in 
the young wheat, are deposited for the most part early in Sep¬ 
tember. Dr. Chapman says the deposit is made from the latter 
end of August till the twentieth of September, and most other 
writers coincide with this, though some of them extend the time 
