a 
156 The Hessian Fly, and its Parasites. 
larva will do little harm, (and may even be useful by stimulating 
the plant to throw out side shoots,) but five or six of them are 
sufficient seriously to check the growth of the plant, or perhaps 
to destroy it entirely.* 
During the winter the insect is in the pupa state, near the 
root of the wheat plant, and usually a little below the surface of 
the earth. In April and May we again find the Hessian fly lay- 
ing eggs on the young wheat, both that which was sown in the 
autumn previous, and the spring wheat, which is of course re- 
cently up. The larve from these eggs become pups about the 
middle of June. es 
' There is no difficulty in tracing the insect as far as the state of 
pupa, and to this point its history is satisfactorily ascertained. 
Regarding the periods of the evolution of the perfect insect, there 
is, however, some obscurity, which numerous observations have 
not whollyfeleared up. The difficulty results in part from the 
fact that in this region, a very large proportion, probably more 
than nine tenths, of every generation of the Hessian fly, is de- 
stroyed by parasites. A great part of the pupe which may be 
collected will evolve some parasitic insect, instead of the Hessian 
fly. It is certain that sometimes, the pup, which became so in 
June, evolve the perfect insect in October following, and that 
other pupee of the same date will not evolve the perfect insect 
until October of the year succeeding. The following seems to 
me the probable history of the matter. 'The pupe, which be- 
came such in the autumn, evolve the perfect insect, partly during 
the next spring, and partly in the summer and autumn following. 
sl ia ot pices “pre eet seior boscy ayaa‘ geil) De 
* It has been repeatedly asserted that the Hessian fly lays her eggs on the ripen- 
ing grain. This error has doubtless arisen from mistaking for the Hessian fly, 
other insects, which in various parts of our country attack the wheat. In the Trans. 
of the Amer, Phil. Soc., 1771, i, 205, Col. Landon Carter has given some account 
of'a pale brownish moth, called by him the fly weevil that destroys the wheat, which 
lays its eggs on the grain. paper on what is probably the same insect, is pub- 
lished by John Lorain in Mease’s Archives of Useful Knowledge, 1812, ii, 47. The 
insect is supposed to be that described by Duhamel du Monceau in his “ Histowe 
Pun Insecte qui devore les Grains de lA 
insect. It is hardly necessary to say that this was not the larva of the Hessia” 
fly. A critical investigation of all these insects is very much to be desired- 
