STATE AGRICULTURAL SOCIETY. 
837 
JOINT-WORM FLY. HOW THE TWO I.ARVyE DIFFER. 
between the Hymenopterous and Dipterous larvae, I supposed 
this character to be so minute and inconspicuous that it could 
only be observed upon making a nice dissection of the mouth. 
A few years later, however, on coming to see the larva of a 
Eurytoma, a glance at its head and mouth assured me I could 
never have confounded a larva of that kind with a Cecidomyia 
larva. I have since examined several Eurytoma larvae of differ¬ 
ent species. I observe in all of them that the head is broad and 
bluntly rounded, not tapering to a point, and the discolored 
transverse line formed by the jaws is placed at the very end of 
the head. In the Cecidomyia larvae on the other hand, the V 
mark is invariably seen a short distance back from the anterior 
end, the head being retracted and thus appearing much as though 
the insect, if it had not, as the common expression is, bit off its 
own nose, had accomplished an equally marvellous feat, to wit, 
had swallowed its mouth, whereby the jaws come to be seen 
partly down its throat. It is only when they are in use that, in 
the larvae of the Cecidomyia;, these jaws, these minute black 
lines, are moved forward to the orifice at the anterior end of the 
head; at all other times they are retracted and are situated a 
short distance back from the end, being quite visible through the 
transparent skin which overlies them. 
Thus the highly important fact is, I think, well authenticated — 
a Cecidomyia larva occurred in this diseased Virginia wheat, as 
well as a Eurytoma larva — the one being found in the same kind 
of cavities or cells in which the other occurred. The wheat 
which I examined was green and succulent. The worm in it was 
at that time one tenth of an inch long. 1 his is the average 
length of the mature larva; in the genus Cecidomyia, although 
there are some species which grow to twice this size. On the 
other hand, it is from the dry straw that the Eurytoma larva 
has been taken, so far as appears. It certainly looks, therefore, 
as though this Cecidomyia larva might leave the wheat and go 
into the ground before the crop fully ripens and is harvested, 
whereby it has wholly eluded observation, its evacuated cells 
perhaps becoming so much altered and effaced that they are not 
liable to be noticed in the dry straw; whilst the Eurytoma larva 
by feedingupon and consuming the former, in numerous instances 
comes to occupy the cells in its stead, remaining in them till the 
following year, whereby it is this insect only which we obtain 
