SILK-WORMS. 
7 
first ring, which is smaller than those which fol- 
low ; and as it has already fastened the skin by 
different threads, and particularly by the hooks of 
the two processes of the anus, which it has already 
attached where it is, it is not difficult to free its 
two first feet, and afterwards to escape in a short 
time from its envelope, by the help of its vermi- 
cular movements. 
Sometimes the covering is broken, or a part re- 
mains attached to the extremity of the caterpillar, 
which cannot always get rid of it. Then it swells 
or enlarges in the part which is disentangled, while 
the envelope compresses the rest of the body : in 
such cases the animal dies, after a greater or less 
exertion . 
If after having eaten much food, the caterpillar, 
approaching the time of casting its skin, had not 
given a great extension to its body, which was 
afterwards diminished in size by firsting and the 
voiding of superfluous matter, it would not have 
been able so easily to have freed itself from its 
skin. A great number of caterpillars change their 
skins entirely in a moment. 
At this period of the life of the caterpillar na- 
ture brings about a favourable crisis, for there is 
thrown out on the surface of its body a humour, 
which being deposited between the old and new 
skin, facilitates the extrication of the animal. The 
surface of the animal is then moist. 
