~~ 
Insects of Shade Trees and Their Control. A” 
Successive defoliation in many instances kills the trees. The walnut 
caterpillar is more abundant and therefore more destructive some 
years than others. 
How recognized—When this insect is present pieces of leaves 
begin to disappear in late summer and early fall, eaten by the gre- 
gariously feeding caterpillars, which when full grown are black, 
covered with dirty gray hairs, and nearly 2 inches in length. When 
disturbed caterpillars rear at head and tail ends (fig. 27) in an 
unusual manner. On the trunk and larger branches. of infested trees 
large clusters of caterpillars or their cast skins may be observed. 
The insect and its habits—On maturity the caterpillars crawl 
down the trunk of the tree an inch or two into the ground and there 
transform into chrysalids. In this shape they overwinter, remaining 
in the ground until the 
following July, when the 
moths issue from them and 
lay their whitish eggs in 
clusters of 75 to 100 on the 
underside of the leaves se- 
lected as food for the cater- 
pillars that hatch from 
them. The habit of feeding 
and molting gregariously 
is a characteristic of this 
insect. 
Remedies.—Collect and 
destroy the clustered cater- 16. 28.—Caterpillar of cottonwood dagger moth. 
pillars feeding on twigs or Siig 
molting on the trunk and branches. Failing this, and if the facilities 
are at hand, spray infested trees with lead arsenate (p. 11). 
COTTONWOOD DAGGER MOTH.” 
How injurious—In prairie regions the caterpillar of the cotton- 
wood clagger moth is a serious enemy of cottonwood and willow 
trees, which it often strips of foliage. As these trees are important 
in these regions for purposes of timber and shelter, this defoliation 
is a serious matter. 
The insect and its habits—The caterpillar (fig. 28) is densely 
covered with long, soft, drooping, yellow hairs, bears five rather 
long, stiff tufts of black hairs along the back, and when at rest 
it les curled up on the underside of a leaf. When full grown it 
retires to some cranny where a silken cocoon, intermixed with its 
hairs, is spun and within it the change to chrysalis takes place. 
23 Apatela populi Riley. 
