36 Farmers’ Bulletin 1169. 
wandered in search of suitable feeding or transformation grounds, 
has been frequently reported. 
How to recognize its presence.—In early summer leaves of hard- 
wood trees or shrubs may show signs of having been eaten by cater- 
pillars with blue head and silvery, diamond-shaped spots down the 
middle of the back (fig. 19, 73). When not feeding, these cater- 
pillars cluster on the trunks and large limbs. In a wind they drop 
to the ground or hang from the tree by silken threads. 
Seasonal history and habits—On approaching full growth, about 
early June, many of the caterpillars abandon the tree and settle in 
sheltered places for pupation (fig. 19, 74). Stones, fences, and wood 
piles serve their purpose. They remain in this state (fig. 19, 15) 
about two weeks and early in July the pup turn into moths (fig. 19, 
10,11). A little later the females lay their eggs in bands of about 150 
around slender twigs (fig. 19,72). By fall the young caterpillars are 
fully developed within the eggs, pass the winter thus, and emerge the 
following spring about the time leaves begin to unfold. 
Remedial measures—Between the spells of abundance this insect 
is kept in check by natural agencies, chiefly parasitic and predacious ~ 
insects and birds as well as unfavorable weather conditions. 
Destruction of egg masses, caterpillar clusters, and pupe in season, 
either by hand picking and burning or by daubing with creosote or 
spraying with kerosene emulsion or any of the standard miscible oils 
on the market, will aid materially in checking the pest. Finally, in 
the care of choice trees and where the necessary apparatus is available 
early spring spraying with lead arsenate (p. 11) of the trees known 
to be infested, if thoroughly done, will effectively check injury for 
the season. 
° 
SPRING CANKERWORM™® AND FALL CANKERWORM.”* 
Character and extent of injury.—Caterpillars, which because of the 
peculiar loop they make of their bodies are variously known as 
“ measuring worms,” “spanworms,” or “loopers” (fig. 20), are fre- 
quently found devouring the leaves of forest and shade trees of 
the eastern United States. Of the numerous species of loopers 
the cankerworms are among the few species that attack both 
fruit and shade or forest trees and occasionally become so numerous 
as completely to defoliate trees on large areas. While as a rule 
healthy trees replace their foliage, repeated defoliation frequently 
leads to attack, especially on oaks, by bark and wood boring insects, 
which habitually thrive on weakened trees and ultimately cause their 
death. The fall cankerworm is the species usually injurious on shade 
trees, the spring cankerworm being principally an orchard insect. 
16 Paleacrita vernata Peck. 18 Alsophila pometaria Harr. 
