TREES, SHRUBS, VINES AND PLANTS. 377 



ing with arsenate of lead close around the webs, so that the leaves 

 next to be enclosed shall have been poisoned, is also a good method 

 of control. Numerous natural enemies of this insect aid man by 

 holding it in check to some extent. 



CANKER WORMS. 



The canker worms are two closely related insects, known as the 

 Fall Canker Worm and the Spring Canker Worm. In both species 

 the caterpillar is an " inch worm " or " looper; " in both the cater- 

 pillar feeds during the spring months, and when through feeding, 

 leaves the tree to pupate in the ground ; in both the female moth 

 is wingless; and in both the eggs are laid by the wingless female 

 on the twigs of the tree, to which she must, therefore, crawl from 

 the ground. 



The moths of the fall canker worm come out of the ground dur- 

 ing warm days in late October, November and early De- 

 cember, and the females crawl up the trees to the twigs, where 

 they lay their eggs in clusters. These eggs hatch about the time 

 the leaves appear the following spring, and the caterpillars feed for 

 four or five weeks until full grown, then go into the ground to pu- 

 pate, the moths from the pupae appearing late in the fall, as al- 

 ready stated. While the caterpillars are feeding they will, if dis- 

 turbed, spin down from the trees on silken threads. 



The spring canker worm moths come out of the ground during 

 the first warm days of spring, even in February in some cases, 

 crawl up the trees to the twigs and lay their eggs. These soon 

 hatch and the caterpillars feed during about the same months as 

 those of the fall canker worm, leave the tree at about the same 

 time and pupate in the ground, but the moths do not emerge that 

 year, spending the winter as pupae in the ground. 



These insects are quite general feeders, consuming the leaves of 

 the apple, elm, chestnut, pear, oak, hickory, box-elder, maple and 

 other trees. As the eggs are laid on the twigs by wingless females, 

 it is evident that anything which will prevent these females from 

 climbing the trees will be effective, and accordingly sticky bands 

 and metal deflectors are extensively used. In general the sticky 

 material known as " Tree Tanglefoot " has proved the most sue- 



