194 STATES OF INSECTS. (Larva.) 
the larva ceases eating altogether; it becomes languid 
and feeble, its beautiful colours fade, and it seeks for a 
retreat in which it can undergo this important and some- 
times dangerous and even fatal operation in security. 
Here, either fixing itself by its legs to the surface on 
which it rests, or, as is the case with many caterpillars, 
by its prolegs, to a slight web spun for this purpose, it 
turns and twists its body in various directions, and alter- 
nately swells and contracts its different segments. ‘The 
object of these motions and contortions seems to be, to 
separate the exterior skin, now become dry and rigid, 
from the new one just below it. After continuing these 
operations for some hours, resting at intervals without 
motion, as if exhausted by their violence, the critical mo- 
ment arrives: the skin splits in the back, in conse~ 
quence of the still more violent swelling of the second or 
third segment: the opening thus made is speedily in- 
creased by a succession of swellings and contractions of 
the remaining segments: even the head itself often di- 
vides into three triangular pieces, and the inclosed Jarva 
by degrees withdraws itself wholly from its old skin. 
All larvee, however, do not force their way through this 
skin in precisely the same place. Thus, those of the haw- 
thorn butterfly (Pzeris Crategi),.according to Bonnet», 
make their way out by forcing.off what may be called 
their skull, or the horny part of their head, without split- 
ting the skin, which remains entire; others have been 
observed to make their way out at the side and the 
belly. Reaumur noticed the larva of 2ygena Filipen- 
dule, previously to its last moult, actually biting off and 
detaching several portions of its old skin; and before this, 
® (Huor, ii. 71. 
