120 THE PESTS OF THE FAKM. 



of the same color on the back. Some are green, with two white 

 stripes c. i the back. The head and the feet partake of the general 

 color of the body ; the belly is paler. When not eating, they re- 

 main stretched out at full length, and resting on their fore and hind 

 legs, beneath the leaves. When fully grown and well fed, they 

 measure nearly or quite one inch in length. They leave off eating 

 when about four weeks old, and begin to quit the trees ; some creep 

 down by the trunk, but great numbers let themselves down by their 

 threads from the branches, their instincts prompting them to get to 

 the ground by the most direct and easiest course. When thus de- 

 scending, and suspended in great numbers under the limbs of trees 

 overhanging the road, they are often swept off by passing carriages, 

 and are thus conveyed to other places. After reaching the ground, 

 they immediately burrow in the earth, to the depth of from two to 

 six inches, unless prevented by weakness or the nature of the soil. 

 In the latter case, they die, or undergo their transformations on the 

 surface. In the former, they make little ' cavities or cells in the 

 ground, by turning round repeatedly and fastening the loose grains 

 of earth about them with a few silken threads. Within twenty- 

 four hours afterward*, they are changed to chrysalids in their cells. 

 The chrysalis is of a light brown color, and varies in size according 

 to the sex of the insect contained in it ; that of the female being 

 the largest, and being destitute of a covering for wings, which is 

 found in the chrysalis of the males. The occurrence of mild 

 weather after a severe frost stimulates some of these insects to burst 

 their chrysalis skins and come forth in the perfected state ; and 

 this last transformation, as before stated, may take place in the au- 

 tumn, or in the course of the winter, as well as in the spring ; it is 

 also retarded, in some individuals, for a year or more beyond the 

 usual time. They come out of the ground mostly in the night, 

 when they may be seen struggling through the grass as far as the 

 limbs extend from the body of the trees under which they had been 

 buried. As the females are destitute of wings, they are not able to 

 wander far from the trees upon which they had lived in the cater- 

 pillar state. Canker-worms are therefore naturally confined to a 

 very limited space. 



In order to protect our trees from the ravages of canker-worms, 

 where these looping spoilers abound, it should be our aim, if pos- 

 sible, to prevent the wingless females from ascending the trees to 

 deposit their eggs. This can be done by the application of tar 

 around the body of the tree, either directly on the bark, as has 



