THE HESSIAN FLY. 
571 
represented by Mr. Lesueur, in the plate designed to accom¬ 
pany Mr. Say’s description of the insect. 
The following brief history of the habits and transfor¬ 
mations of the Hessian fly will be found to agree essen¬ 
tially with the excellent observations on this insect, written 
in the year 1797, by Dr. Isaac Chapman, and published 
in the fifth volume of the “ Memoirs of the Philadelphia 
Societv for Promotino; Agriculture,” and with the more 
full and equally valuable history of the insect, by Jona¬ 
than X. Havens, Esq., contained in the first volume of 
the “ Transactions of the Society for the Promotion of 
Agriculture, &c., in Xew York.” Mr. Herrick has kindly 
permitted me to make free use of his valuable account of 
this insect, contained in the forty-first volume of “ The 
American Jounial of Science,” and of other information 
communicated by him to me in various letters. He has 
spent some time in carefully observing the habits of the 
fly, during many years in succession, after having fitted 
himself for the task by the study of the natural history 
of insects in general. His statements therefore may be 
relied upon, as in the main correct. Moreover, they are 
corroborated by tbe observations of many other persons, 
published in various works, which have been consulted in 
the course of my investigations. 
Of this insect, two broods or generations are brought to 
maturity in the course of a year, and the flies appear in 
the spring and autumn, but rather earlier in the Southern 
and Middle States than in Xew England. The transfer- 
mations of some in each brood appear to be retarded beyond 
tbe usual time, as is found to be the case with many other 
insects ; so that the life of these individuals, from the egg 
to the -winged state, extends to a year or more in length, 
whereby the continuation of the species in after years is 
made more sure. It has frequently been asserted, that the 
flies lay their eggs on the grain in the ear; but whether 
this be true or not, it is certain that they do lay their eggs 
