92 Farmers’ Bulletin 1169. 
How recognized.—Affected parts bear greater or smaller numbers 
of protuberances or deformities of various more or less uniform 
shapes and sizes. These are provided with openings and when fresh 
contain one or more pink tinged, bluish green, immature insects. 
Habits —The insects in the galls attain maturity in the fall, and in 
this state pass the winter in cracks of the bark on hackberry or 
among the débris on the ground. At the time buds on these trees 
begin to swell and open in the spring the insects begin feeding on the 
tender growth and laying eggs on the leaves. In about three weeks 
the eggs hatch and the feeding of the ensuing insects causes swelling 
of the tissue around them until they are almost completely inclosed. 
Thus one life round is completed in a year. 
Remedies.—In the rare instances when remedial measures are war- 
ranted, application of a contact insecticide like kerosene emulsion 
(p. 12-13) or water-soluble oil (p. 13), at the time the young appear 
on the leaves in the spring and before the galls are entirely closed, 
should give considerable relief. 
OAK GALL-INSECTS.* 
How injurious —Over 400 species of gall-making insects are known 
to affect oaks, and great is the variety of these galls in shape, size, and 
structure, all parts of the tree from the root up, including buds, 
flowers, and fruits, being subject to these deformities. A tree or part 
of it, particularly its foliage, may be literally covered with the galls 
of one or more species or may be completely changed by them, and, 
while the aspect is not always agreeable, the life or health of the tree 
is never menaced thereby. 
How recognized.—FKither the size, the shape, the color, or the 
number of these abnormal growths leads to their ready detection, 
especially on the foliage. The specific identity of the particular 
architect, however, can be determined only by the special student of 
this group of insects. To tree wardens this identity is of secondary 
consideration, since the injury is so rarely of more than secondary 
importance. 
Habits —No general outline of the habits applying to all these gall 
builders can be given. Not all of them are known, and there are too 
many even of those known for enumeration in this bulletin. Roughly, 
however, the habits are as follows: 
The gall wasps—In some of the gall wasps a life cycle has been 
found made up of several generations, only one of which consists of 
the two sexes. The females of the original generation usually lay 
their eggs between March and May, and frequently during the period 
from November to January, while those of the paired generation lay 
their eggs between June and August. The eggs are laid either on or 
in the particular portion of the plant they infest, and the developing 
"68 Gall wasps (family Cynipidae) ; gall gnats (family Itonididae). 
, 
=— Ts 
2 ati ey 
