1 62 THE INSECT WORLD. 



We will now see how the insect delivers itself from the last skin. 

 To quit the pupa case is not so laborious an operation as it was for 

 the same insect to quit the caterpillar's skin. This is because the 

 pupa case is drier ; it does not adhere to every part of the body, and 

 is brittle. Those insects which are enclosed in a cocoon free them- 

 selves of the pupa envelope in the cocoon itself. To witness the 

 last operation, the cocoon may be opened, and the pupa drawn out 



Fig. 128. Chrysalis of the Large Tortoise-shell Butterfly ( Vanessa polyckloros) whose different 



parts have been opened before they were fastened down. 



(a, wings ; bb, antennae ; t, trunk, or proboscis.) 



of it with care. If it is then placed in a box, the metamorphosis 

 may be observed. To study this last evolution more at his ease, 

 Reaumur covered a large extent of the wall of his study with pupae 

 of the Vanessa polychloros and other species. 



When the parts of the body of the insect have attained a certain 

 degree of solidity within the envelope, it has no great difficulty in 

 making the thin and friable membrane which surrounds it split in 

 different places. If it even distends itself or moves, a small opening 

 will be made in the dried skin. If the movements persist, the 



well-known fact that many insects remain in this state a variable time the Small 

 Eggar (Bombyx lanestris) sometimes as many as seven years. ED. 



