LEPIDOPTEROUS INSECTS. ily 
pillars originating from eggs thus deposited are 
solitary, as those originating from clustered eggs 
are gregarious. The latter moreover remain in 
company so long as they are in the caterpillar state, 
while the former always occur dispersed, and lead a 
solitary life. In this manner, then, the caterpillars 
under notice live from the time they are hatched, 
and even exhibit the same disposition when they 
prepare for their change into the chrysalis state, as 
we shall afterwards see. 
** As to their manner of growth, such caterpillars 
differ widely from other animals which grow re- 
gularly in all their parts as they are supplied with 
nourishment ; but our caterpillars, on the contrary, 
grow only in their inward parts, whose increase 
puffs out the skin or outer covering that does not 
grow, and hence becomes too small, so that at 
length it must give way. In fact, it actually does 
so, and this happens more than once during its life ; 
a circumstance which I term the casting of the skin, 
and which is thus performed: A few days before 
the skin is cast, the caterpillar remains nearly sta. 
tionary in the same place, and leaves off eating. 
About this period, the neck or hind part of the 
head may be observed to swell, in consequence of 
which the old skin becomes more stretched, the 
inner skin is separated from the outer, and in some 
smooth caterpillars the head may be decemed shi- 
ning through. The old skin becomes gradually 
