LEPIDOPTERA. 335 



When not eating, they remain 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 descending, 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 afterwards, 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 occur- 

 rence 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 autumn, 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 caterpillar state. Canker-worms 

 are therefore naturally confined to a very limited space, from 



* In the year 1841, the red-currant flowered, and the canker-worms appeared, 

 on the fifteenth of May. The insects were very abundant on the fifteenth of 

 June, and on the seventeenth scarcely one was to be seen. 



