The Life-History and Anatomy of Butterflies 
though there are exceptions to this rule. The young larva, having 
emerged from the egg, grows for a number of days, until the 
epidermis, or true skin, has become too small. It then ceases 
feeding, attaches itself firmly to some point, and remains quiet for 
a time. During this period certain changes are taking place, and 
then the skin splits along the middle line from the head to the 
extremity of the last segment, and the caterpillar crawls forth from 
the skin, which is left behind it, attached to the leaf or branch to 
which it was fastened. The skin of the head sometimes remains 
attached to the head of the caterpillar for a time after it has 
moulted, and then falls off to the ground. Ordinarily not more 
than five, and frequently only four, moults take place between 
hatching from the egg and the change into the chrysalis. In cases 
where caterpillars hibernate, or pass the winter in inaction, a long 
interval necessarily elapses between moults. Some arctic species 
are known in which the development from the egg to the perfect 
insect covers a period of two or three years, long periods of 
hibernation under the arctic snows taking place. The manner in 
which the caterpillar withdraws itself from its exuviae, or old skin, 
is highly interesting. Every little spine or rough prominence is 
withdrawn from its covering, and the skin is left as a perfect cast 
of the creature which has emerged from it, even the hairs and 
spines attached to the skin being left behind and replaced by 
others. 
The Food of the Caterpillar.—The vast majority of the cater¬ 
pillars of butterflies subsist upon vegetable food, the only excep¬ 
tions being the singular one already noted in which the larvae 
feed upon scale-insects. Some of the Hesperiidce, a group in 
which the relationship between butterflies and moths is shown, 
have larvae which burrow in the roots and stems of vegetation. 
Duration of the Larval State.— The duration of the larval state 
varies greatly. In temperate climates the majority of species exist 
in the caterpillar state for from two to three months, and where 
hibernation takes place, for ten months. Many caterpillars which 
hibernate do so immediately after emerging from the egg and be¬ 
fore having made the first moult. The great majority, however, 
hibernate after having passed one or more moults. With the 
approach of spring they renew their feeding upon the first reap¬ 
pearance of the foliage of their proper food-plant, or are trans¬ 
formed into chrysalids and presently emerge as perfect insects. 
io 
