1863.] 
331 
iug my boxes of galls almost daily, and of removing all the flies that 
appeared. I noticed that the flies that tirst appeared in the box con¬ 
taining galls of G. q. operator were nearly all males, while the last that 
came out were mostly females. This species continued to come out in 
great numbers for more than two weeks, in the latter part of June, 
and were followed by a swarm of parasites of several species. The act 
of copulating at once took place, and several specimens were removed 
from, the box for examination while in coitu. May we not safely infer 
that the last step in the act of procreation—that of ovipositing—-would, 
under favorable circumstances, have soon followed ? 
The leaf and flower buds for the following year are fully formed at 
the season when many of the vernal gall-flies make their appearance, 
and probably many species then deposit their eggs in them.* The ap¬ 
pearance of the oak-apple galls and others upon particular parts of the 
leaf or on the petiole is difficult to explain. It is possible that these 
tiny beings are guided by an instinct so delicate and unerring as even 
to touch the embryo leaf, with the ovipositor, at the proper place. 
Again, the life force of the tree, that cooperates so mysteriously in the 
formation of the gall, probably, begins to act in the bud. The egg 
may, if only placed in contact with the leaf, provoke into activity this 
force; thus not rendering it necessary that it be deposited in the sub¬ 
stance of the leaf. 
The theory of leaf development now everywhere admitted to be cor¬ 
rect, that the parts of the flower are but modified forms of the leaf, 
brings into view a principle of adaptation in nature that only needs to 
be extended slightly to show that the cells of G. q. seminator and ope¬ 
rator are modified leaves, and that the silky fibres covering the cells 
are only a monstrous development of the pubescence always obser¬ 
vable on young leaves; and that such galls as G. q. hatatus and tuber 
are caused by the depositing of the eggs of the insect while the stem 
exists, as it certainly does exist, in the bud. 
C. q. punctata, described in this paper, deposits her eggs in the wood of 
branches of several years growth, and the gall-flies make their appearance, 
judging from my sj)ecimens, some days before the leaves appear. 
I would name C. q. seminator, operator, hatatus, and tuber, as species that pro¬ 
bably oviposit in the young buds. There are probably others also. 
