CANKERWORMS SNODGRASS 



325 



ance characteristic of canker worm injury. The very young worms 

 make mere pits or punctures in the leaves, but the older ones devour 

 great holes in them, finally reducing them to ragged skeletons or 

 bare stems (fig. 10). The damage done to apple trees may be very 

 considerable in cases of bad infestation, if remedies are not applied, 

 but the orchardist can control the pest by thorough spraying with 

 arsenate of lead, which, however, to be most effective should be done 

 when the worms are young. In orchards that are known to be in- 

 fested with cankerworms, the trunks of the trees may be banded in 

 late fall and early spring with sticky substances or with cotton bat- 

 ting, in order to prevent the female moths from ascending them. 



Fig. 10. — Apple leaves destroyed by cankerworms 



So similar are the two species of cankerworms, both in the larval 

 and in the adult stages, that even entomologists did not distinguish 

 between them for nearly two hundred years after they were first 

 called cankerworms. The name " cankerworm," however, did not 

 originally belong to either of the two species of caterpillars to which 

 we now apply it in America. At the time the English translation 

 of the Bible was made, the word " canker " referred to most any de- 

 structive caterpillar. 



Besides the cankerworms there are numerous other species of 

 measuring worms, or spanworms, as they are also called, most of 

 them having the same general appearance as the cankerworms. 

 Some are well-known pests on cultivated trees and shrubs, and others 

 are met with only occasionally, looping along in solitude or project- 

 ing motionless from a twig or the edge of a leaf. The majority of 



