SKIN SHEDDING . 
57 
attached by its abdominal legs to the under surface of the twig 
or leaf upon which it has been feeding. Many species spin a slight 
web, or carpet of silk, in which they attach their posterior legs, 
as observed by Pallas in Apatura iris (Purple Emperor), and in 
this manner await their change, which appears to be attended with 
much uneasiness to the insect. The whole body is wrinkled and 
contracted in length. In the Sphinx this contraction occurs to 
so great an extent in some of the longitudinal muscles of the 
anterior and middle part of the body, that the larva assumes 
that peculiar attitude from whence the genus derives its name. 
In this attitude the larva remains for several hours, during which 
there are occasionally some powerful contractions and twitchings 
of its whole body; the skin becomes dry and shrivelled, and is 
gradually separated from a new but as yet very delicate one which 
has been formed beneath it, and the three or four anterior seg- 
ments are greatly enlarged on their dorsal but contracted on their 
under surface. After several powerful efforts of the larva, the old 
skin cracks along the middle of the dorsal surface of the second 
segment, and by repeated efforts the fissure is extended into the 
first and third segments, and the covering of the head divides 
along the top. The larva then gradually presses itself through 
the opening, withdrawing first its head and thoracic or fore legs, 
and subsequently the remainder of its body, slipping off the skin 
from behind, like the finger of a glove. This process, after the 
skin has once been ruptured, seldom lasts more than a few minutes. 
When first changed, the larva is exceedingly delicate, and its head, 
which does not increase in size until the skin is again changed, is 
very large in proportion to the rest of its body. In a few hours 
the insect begins to feed again most voraciously, particularly after 
it has entered its last skin, when its growth is most rapid. Thus, 
a larva of Sphinx ligustri, which at its last change weighed only 
about nineteen or twenty grains, at the expiration of eight days, 
when it was full grown, weighed nearly 120 grains. 
“ Most larvae remove to fresh plants immediately after chang- 
ing their skins, but some, as the larvae of a beautiful moth, 
Episema coernleocephala , devour their old skins almost immediately 
they are cast, and sometimes one another, when deprived of food. 
But it is not merely the external covering which is thrown off 
