808 
ANNUAL REPORT OF NEW YORK 
OAK. LIMBS. 
often dark colored, and very distinct. The middle longitudinal vein arises 
from the middle of the anterior veinlet, but is often obliterated at its com¬ 
mencement. It is widely forked, slightly before it reaches the second 
veinlet sending off a straight and very coarse branch to the outer margin. 
By the inner end of the second veinlet crossing this fork slightly back of 
its commencement a small triangular cell is formed in the center of the 
wing. Westwood, in defining this genus, says this small cell is bounded 
by veins of equal thiokness ; but in all the American gall-flies known to me 
the veins on one or both the anterior sides of this cell are much more 
slender than the one on its posterior side. Finally, the antennas are 
thread-like, or of the same thickness through their entire length, and aro 
about half the length of the body. Their joints are separated by very 
slight constrictions, whereby they are counted with difficulty by the aid of 
a common magnifying glass ; but this instrument is sufficient to show their 
number, even in the smaller species. Westwood states the number of 
joints to be fourteen in the females and one more in the males. Ilartig 
differs with him as to the latter. Brulle (Hymenopt. iv. 635) merely 
cites these authors without affirming anything on this subject himself. 
Had he no specimens at hand whereby to determine a point which appears 
so simple ? Doubtless he had, and on examining them found he was 
unable to decide this matter. For, though the number of these joints 
appears to be constant in the same species, they differ in different species. 
Thus, in the gall-flies of the oak here described, of six species of which I 
possess examples of both the sexes, I find the number of joints to be as 
stated by Mr. Westwood in three only. In two of the others the females 
have but thirteen joints. Whilst in the remaining species, which is the 
Oak-tumor gall-fly now under consideration, the antennae of the males have 
only fourteen and those of the females twelve joints. And in a seventh 
species, only the females of which are known to me, the number of these 
joints amounts to fifteen. It hence appears that the antennae of these 
insects have sometimes one sometimes two more joints in the males than 
in the opposite sex, and that in the latter the number is from twelve to 
fifteen in different species. 
In all parts of the world the oaks are far more infested with gall-flies 
than trees of any other kind. The naturalist Bose during his residence in 
Carolina observed sixteen different kinds of galls, of which eight grew upon 
oaks; but all his endeavors to rear the flies from them were futile. My 
own efforts have been more successful, as will be seen by the accompany¬ 
ing notices. And a number of oak-galls, in addition to those herewith pre¬ 
sented, are known to me, from which I have not yet been able to obtain 
the flies, from some of them parasites having come in their stead. I regret 
that I am unable to refer to the memoir of Bose on the insects of this 
family, long since published in the second volume of the Paris Journal of 
Natural History, and also the Monograph of Brisehke, which appeared a 
few years since at Berlin. Hence I may perchance here be giving as new, 
some species which have already been named in this latter work. 
