LEPIDOPTERA. 151 
to fix itself. After having covered it thus with a kind of thin 
cobweb, it adds different layers of threads on a small portion of 
this surface, im such a manner that the upper one is always smaller 
than that upon which it is laid. In this manner a small hillock 
of silk is formed, the tissue of which is not at all compact. It 
resembles an assemblage of loose or badly interwoven threads. 
The membranous feet of the caterpillar are armed with hooks of 
different lengths, with the aid of which it suspends itself. By 
alternately contracting and elongating its body, it pushes its 
hindermost legs against the hillock of silk, presses against it the 
hooks of its feet so as to get them better entangled, and lets its 
body fall in a vertical position. 
It remains hanging thus, often for twenty-four hours, during 
which time it is occupied in a difficult task, that of splitting its 

Figs. 104, 105.—Chrysalides of the small Tortoise-shell Buttertly freeing themselves from 
the Caterpillar skin. 
skin. , In order to effect this, it incessantly curves and recurves 
its body (Fig. 102), until at last a split appears on the skin of the 
back, and through this split emerges a part of the body of the 
chrysalis. This acts as a wedge, and little by little the split widens 
from the head to the last of the true legs, and beyond them. 
Then the opening is sufficient to allow of the chrysalis drawing 
out its anterior portion from the envelope, which it immediately 
does. To set itself entirely free, the chrysalis lengthens and 
shortens itself alternately (Fig. 105). Hach time that it shortens 
