580 
DIPTEEA. 
many observers, that there are three generations of this 
insect in a year,” “ two ” being completed “ before har¬ 
vest.” This opinion was revived, in 1821, by Mr. James 
'Worth, of Sharon, Pennsylvania.* According to him, the 
second brood of flies, which appears early in June, had been 
altogether overlooked, or confounded with the spring brood. 
Their “ eggs were lain on the upper leaves of the weakest 
or stunted wheat, and the larvae became lodged about the 
two upper joints, but most about the upper.” Being very 
numerous, and crowded together, many of the larvae perished 
for want of food, and many also were destroyed by parasites. 
Enough, however, remained alive to continue the race; and 
the flies were evolved from them at irregular intervals, and 
continued laving from the 15th of August till October, when 
the earliest of their progeny entered on the fly state ; thus 
making, during the year, as remarked by Mr. Worth, “ three 
complete broods, and partially a fourth.” 
Mr. Say, though he does not appear to have been fully 
acquainted with the history of the insect, has recorded the 
occurrence of the fly in June. His remarks are these: 
“ The perfect fly appears early in June, lives but a short 
time, deposits its eggs, and dies; the insects from these eggs 
complete the histor}’ by preparing for the winter brood.” 
In the year 1833, Mr. Herrick saw a Hessian fly laying 
eggs on the 3d of June, another on the 5th, and a third on 
the Tth of the same month. The fact of the occasional ap¬ 
pearance of the flies as late as the 12th of June, when Mr. 
"Worth found the insects in all their stages, seems to be well 
established; while it is equally certain that ordinarily only 
two broods are brought to perfection in the course of one 
year. '\"arious circumstances may contribute to accelerate 
or to retard a portion of each brood; and, hence, some of 
the flies may be found from the middle of April to the mid¬ 
dle of June, and others from the beginning of August till 
December. These circumstances have been so frilly consid- 
* See American Farmer, Vol. III. p. 188 . 
