464 LEPIDOPTERA. 



very young, tliey have two minute warts on the top of the 

 last ring ; and they arc then generally of a blackish or 

 dusky-brown color, with a yellowish stripe on each side 

 of the body ; there are two whitish bands across the head ; 

 and the bellv is also whitish. When fully 



Fig. 231. ^. " ... 



gi'own (Fig. 231), these individuals become 

 ash-colored on the back, and black on the 

 sides, below which the pale yellowish line 

 remains. Some are found of a dull greenish-yellow and 

 others of a clay color, with slender interrupted blackish lines 

 on the sides, and small spots of the same color on the back. 

 Some are green, with two white stripes on the back. The 

 head and the feet partake of the general color of the body ; 

 the belly is paler. 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 surfice. 

 Fig. 232. I^^ the former, they make little cavities or cells 

 ^^^^ (Fig. 232) in the ground, by turning round re- 

 ^^am^ peatedly and fastening the loose grains of earth 

 about them with a few silken threads. Within twenty-four 



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

 the 15th of May. The insects were very abundant on the 15th of June, and on 

 the I7th scarcely one was to be seen. 



