THE CHANGE OF SKIN. 43 



increased, that one can scarcely imagine how it could 

 ever have been contained in its old integument j for a 

 time its body remains very soft, and the creature is 

 languid and dull, but this condition soon passes away, 

 the new epidermis acquires the firmness of its pre- 

 decessor, and the larva resumes its old business of 

 eating with a vigour which seems to indicate an 

 earnest desire to make up for the time wasted in 

 moulting, or a peculiar pleasure in the exercise of its 

 newly-acquired tools. These observations on the 

 change of skin apply more especially to such larvae as 

 the caterpillars of the Butterflies and Moths, in which 

 all the phsenomena connected with the metamor- 

 phosis may be observed with the greatest ease. In 

 the case of other insects, observations are frequently 

 attended with some difficulty ; but they do not difier 

 in any important point from the above description, 

 and the number of those in which no change of skin 

 takes place is comi^aratively small. 



The larvse of most insects appear to moult about 

 three times, — a good many, however, change their skins 

 four times, and in those which remain in the larva 

 state for a long period, the moultings are still more 

 numerous. During all this stage of existence the de- 

 velopment of the internal parts is advancing, and after 

 the last change of skin, the rudiments of the wings 

 are formed, and frequently show themselves externally 

 in the form of humps upon the segments which corre- 

 spond with the thorax of the perfect insect. 



Another and a more important change is now about 

 to take place, for when the last larva- skin is cast off" 

 the insect is to present itself in a new form, which, 

 although still usually far removed from that which it 

 is ultimately destined to assume, nevertheless re- 



