472 
Saw-flies, Gall-flies, Ichneumons, 
common bullet gall, H. globulus , of the small twigs, J to f inch in diam¬ 
eter, has the kernel surrounded by a hard woody substance. 
Fig. 664. —An oak-apple, or fibrous gall of the California live-oak; in upper figure the 
gall shown in position on the oak-twig; in lower, a gall cut open to show the inside. 
(Upper figure slightly reduced; lower figure natural size.) 
In California the white or valley oaks bear very commonly conspicuous 
large white spherical to kidney-shaped galls (Fig. 665) which are attached 
to the branches, and often occur in such abundance as to make the injured 
tree look like some new kind of fruit-tree in heavy bearing. This gall is 
caused by the gall-fly Andricus calijornicus , one of the largest of the Cyni- 
pidae, and the gall itself attains a larger size than any other known to me. 
It begins as an elongate swelling underneath the bark of the fresh twigs, 
but soon breaks through as a shining, smooth excrescence rapidly increasing 
in size. A single gall is inhabited by from six to a dozen larvae. A curious 
oak-leaf gall is the jumping seed-gall (Fig. 666), a small and shot-like gall which 
