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 withdrawn from its covering, and the skin is left as a perfect cast 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 larva; 

 feed upon scale-insects. Some of the Hespertidce, 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. 



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