Wasps, Bees, and Ants 
47 1 
“oak-apples.’’ One of these is the fibrous oak-apple of the scarlet oak, 
i to 2 inches in diameter, produced by the gall-fly Amphibolips coccinea. 
Fig. 66i. —Galls on leaf of California white oak. (Natural size.) 
This gall is distinguished by having a small hollow kernel in the center of 
the gall, in which 
the single larva lives, 
the space between 
the kernel and the 
dense outer layer of 
the gall being filled 
with fibers radiating 
out to the surface 
from the kernel. The 
spongy gall of the red 
and black oak, made 
by A m phib oli p s 
spongifica , has the 
space between kernel 
and outer wall filled 
by a porous, spongy 
mass. In the “ emp¬ 
ty oak-apples,” the 
larger one of the 
scarlet and red oaks, 
Holcaspis inanis, 2 
inches or more in 
diameter, and the 
smaller, of the post¬ 
oak, H. centricola , } 
inch or less in diam¬ 
eter, the space be¬ 
tween kernel and 
outer wall contains 
only a few slender silky filaments which suspend the kernel in place. 
Fig. 663, Fig. 662. 
FiG. 662.—Galls on twigs of California white oak; upper figure, 
a gall split open longitudinally. (Natural size.) 
Fig. 663.-— Galls on leaf. (After Jordan and Kellogg; natural 
size.) 
The 
