18 INSECT AND FUNGOUS ENEMIES OF THE APPLE. 
westward to Lake Superior, and it is also common in California. 
The spring cankerworm (Paleacrita vernata Peck) is particularly 
abundant in the Mississippi Valley from Texas to Lowa, ranging 
eastward to Maine. It is common in the orchard section of northern 
Virginia, western Maryland, and West Virginia. The two species 
thus overlap in their distribution and both may be concerned in the 
defoliation of an orchard, especially in the northeastern part of the 
United States. 
The fall cankerworm deposits its eggs in ringlike masses on the 
twigs during late fall or in warm periods during the winter. The 
spring cankerworm oviposits in early spring, before the buds start, 
in irregular masses under bark scales, along the trunk and limbs, 
iG. 9.—Spring ecankerworms. Enlarged. 
or more or less promiscuously. The young larve have hatched 
and are attacking the foliage by the time the young leaves are well 
free from the bud scales. They often occur in such enormous num- 
bers that the trees are quickly defoliated, leaving only the midribs 
of the leaves (see fig. 10), the orchard from a distance appearing as 
if swept by fire. After the larvee mature they go to the ground and 
pupate just below the surface, and are easily destroyed by plowing 
and cultivations during the late spring and early midsummer. There 
is only one generation of the insects each year, the adults of the fall 
species coming out in late fall and winter, and those of the spring 
species "in early spring, as stated. The adult females of both species 
are wingless and must crawl up the trunks of the trees to oviposit. 
492 
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