THE ENTOMOLOGIST. 5 
a yellowish colour; in the space between them and the 
margin is a circle of scabrous points. In the interior is a 
large larva-cell, and a hole in the convex septum shows 
where the imago has escaped.—G@. L. Mayr. 
Aphilothrix Corticis is accompanied in the gall by Synergus 
incrassatus, which has already been mentioned as a tenant in 
the gall of Aphilothrix Radicis, and is one of the winter 
species, Dr. Mayr having divided the Synergi into winter 
flies and summer flies according to the time of their appear- 
ance. The following note refers to the likeness of oak-galls 
to organs of the oak. The differences of the parts of an 
organism, such as the oak, and the means which successively 
occasion these differences, are of much interest, as the result 
of one agent,—the circulation in the living form. But the 
differences between the kinds of oak-galls are more remark- 
able: they are also the products of the circulation of the oak, 
and therefore it would seem to be likely that they must 
resemble the native products of that circulation; and such in 
some kinds is the case. But two kinds of galls, quite different 
in structure, may be found in close contiguity, or almost 
connected, on the oak; and it remains to be ascertained 
whether this difference is caused by the puncture, by the egg, 
by the grub, or by the joint influence of these three.—Francis 
Walker. 
Aphilothrix Rhizomatis.—This occurs Fig. 4, 
partly under ground and partly on those ~ 
shoots which are but slightly raised above 
the ground: a roughness or unevenness in 
the bark is observable, and a crack or 
furrow appears, in which the galls are 
seated in sparse clusters: the visible por- 
tion of each gall is conical or hemispherical, 
or sometimes nearly oval, and of an ochreous 
colour ; at the base of the cone are striz or 
furrows, similar to those on the species next 
to be described, but these vanish towards 
the summit, where no trace of such striz 
is perceptible ; the summit itself is rounded, 
and is pierced in the centre by the imago 
in making its escape. Each gall contains 
one large larva-cell, the exposed portion of 
which is from two to three millemetres in 
A, RHIZOMATIS. 
