254 



APPLIED ENTOMOLOGY 



some distance, spinning a thread as they go, and up which they return 

 to resume their feeding. A sudden jar of an infested tree will cause 

 great numbers to drop or "spin down" several feet in this way. When 

 feeding has been completed the larvae enter the ground and pupate a 

 few inches below the surface in a silken cocoon, from which the moths 

 escape late in the fall. 



Fig. 255. — Fall Canker Worm caterpillars feeding on Elm. Natural size. (From Britton, 

 Eighth Rept. Ent. Co7in. Agr. Exp. Sta. 1908.) 



The Spring Canker Worm {Paleacrita vernata Peck). — The adult 

 male of this species averages slightly less in its wing-spread than the 

 Fall Canker Worm and its wings are somewhat lighter in color. It 

 occurs throughout the Eastern United States except in the South and has 

 also been taken in Texas and California. It is particularly injurious 

 at times in the Mississippi Valley. This pest escapes from its pupa in 

 the ground, as the adult, very early in the spring, and the females crawl 

 up the trees on which they lay their clusters of eggs, frequently under 



