Miscellanies. 157 
and independently of the injury to vegetation, by the hard chrysalids 
interrupting the ascent of the sap, the larve obviously suck the juices 
of the plant for their food. : 
It is the habit of the whole genus Aphis, to which I have referred 
the fly in question, to feed in its larva state on tender succulent plants, 
and on such alone they nidify: this not being the habit of the Tipula, 
nor of the house fly, I did not hesitate on the identification ; and the 
vast disproportion of numbers, taken in reference to the well known 
chrysalids, as stated by me, (there being only a few of the two latter 
and immense numbers of the Aphis, which was selected by me as 
the true parent,) no doubt was left on my mind, that the well known 
chrysalid of the Hessian Fly, in my sod of wheat, had developed nei- 
ther the Musca, nor the Tipula, but the Aphis, to which I referred it. 
In the truth of this opinion I am much strengthened by an intelli- 
gent and highly respectable neighbor, who frequently saw the flies 
in my jar: he declared the kind which I described in my paper, to 
be the identical kind which he the last summer had cut out from the 
flax seed casement of the Hessian Fly in the wheat field, when ma- 
ture and prepared to escape from it; and that the other two kinds, 
the Diptera before named, were so wholly unlike those which he 
thus obtained, that he could not be deceived. 
Upon investigation, I have discovered a great contrariety of opinion 
and festimony on the identity of the Hessian Fly, arising unquestiona- 
bly from such circumstances as may possibly, also, have deceived me. 
Mr. James Vaux, in a communication to a philosophical society, in 
1792, on this subject, says he has frequently seen them [the Hessian 
Fly] in the act of depositing the egg, and that they resemble a “slen- 
der, gaunt, house fly.” 
Judge Buel, in a paper on this subject, in the American Farmer, 
compares them to a musketo, except that they are smaller, and have 
a short bill—certainly, the house fly and musketo have no similarity. 
Some say, from personal observation, that they nidify upon the 
grain exclusively—others, with equal confidence and as I believe 
with more propriety, say exclusively upon the leaf and stalk; the 
parent fly has necessarily been mistaken. 
Some affirm that they finish their nidification by the 20th of Sep- 
tember: Dr. Chapman is of this opinion. Under my own observa- 
tion, they have continued it, destructively, on wheat sown after the 
middle of November. 
