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 laying 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 history 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 7th 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. Various 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 ftilly consid- 



* See American Farmer, Vol. HI. p. 188. 



