47 ° 
Saw-flies, Gall-flies, Ichneumons, 
position, and the interesting response or reaction of the plant to the growth- 
stimulating irritation of the gall-fly larva are subjects which have attracted 
much attention and study, but concerning which much remains to be dis¬ 
covered. In size and shape the galls present amazing variety; some are irreg¬ 
ular little swellings on the leaves, others are like small trumpets, others like 
rosettes or star-like with radiating 
points; on the twigs some are spherical, 
some elongate, and some large and 
reniform. Figs. 657 to 665 show 
something of 
this variety. 
In their interior 
make-up they 
also differ 
much; some 
have a large 
hollow central 
space: 
some 
Fig. 658. Fig. 659. 
Fig. 658.—Galls on leaf of California white oak. (Natural 
size.) 
Fig. 659.—Trumpet-galls on leaves of California white oak. 
(Natural size.) 
are filled with open, spongy tissue, and some are 
solid except for the cells and tunnels of the larvae. 
In some but a single larva lives; in others are three 
or four or a dozen. Externally some are smooth, 
some roughened, some hairy. They occur on leaves, 
branches, and roots in both oak and rose. Only Fig. 660.—Galls on leaf 
a few Cynipid galls are known on other plants ^atural^izeT 11116 ^ 
than these. In the face of the host of species of Cyni- 
pidae found in this country—over 200 gall-making kinds are known, besides 
a score of parasitic species—and their small size and generally similar appear¬ 
ance, we shall not undertake to describe any of the various species. Com¬ 
stock describes in his Manual several of the more common eastern galls, or 
