INSECT ENEMIES OF EASTERN FORESTS 599 
Figure 182.—The oak fig gall (Biorhiza forticornis). (After Felt.) 
large internal cavity, which is hollow except for a single free-rolling 
cell about 149 inch in diameter. 
This cell contains the gall-making 
insect. The adult insect emerges early in May. The galls are usually 
formed on the leaves, but may also appear on the axis of the staminate 
flowers. Not long after the adult insects emerge the galls dry up. 
No injury seems to result from the malformation other than the growth 
itself, and no remedial measure 1s advised. 
Callirhytis (Andricus) 
operator O. 8. is well 
known as one of the first 
species for which an al- 
ternation of generations 
was shown. It infests 
red oak (Quercus bo- 
realis), black oak (Q. vel- 
utina), scarlet oak (Q. 
coccinea), and scrub oak 
(Q. tlicifolia) through- 
out the Eastern States 
and imto ‘Texas. The 
woolly galls on the stam- 
inate flowers, which yield 
the sexual generation, 
consist of spongy masses 
of succulent, fibrous, yel- 
lowish, whitish, or pink- 
ish material. Within 
these filaments are seed- 
NE et 
 S 
Figure 183.—The succulent oak gall (Callirhytis 
palustris). 
(Courtesy Amer. Mus. Nat. Hist.) 
