464 
LEPIDOPTERA. 
Fig. 231. 
very young, they have two minute warts on the top of the 
last ring ; and they are 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 belly is also whitish. When fully 
grown (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 surface. 
Fig. 232. I' 1 the former, they make little cavities or cells 
• (Fig. 232) in the ground, by turning round re- 
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 16th of May. The insects were very abundant on the 16th of June, and on 
the 17th scarcely one was to be seen. 
