178 ROUND THE YEAR 



disengaged integument from slipping back to its 

 former place. When the old skin, like a stocking 

 pushed down the leg, is gathered into a mass of folds 

 close to the extremity of the body, the Insect pro- 

 ceeds to free itself completely, and further detaches 

 the cast skin, which if allowed to remain hanging by 

 its side, would needlessly attract the attention of 

 Birds. How is a pupa, hanging by its tail, and with- 

 out means of holding on by the rest of its body, to 

 attach itself anew, and dislodge the cast skin ? The 

 tip of the abdomen of the pupa bears a pair of pro- 

 minences which are opposable and armed with many 

 small hooks. At their base the abdomen is indented, 

 and forms a kind of elbow, which can be flexed, and 

 used as a means of grasping. The pupa extricates 

 the tip of its abdomen, using the elbow and the 

 hooked forceps alternately as a means of attachment ; 

 it then creeps a short distance along the cast skin, 

 and gets an independent hold of the hillock of 

 threads. Next it sets its body spinning, first in one 

 direction, and (if necessary) in the opposite direc- 

 tion by turns. The hooks cut through the threads 

 which hold up the cast skin, and this falls to the 

 ground. 



Where the pupa is to hang by its tail, head down- 

 wards, the artifice of the Peacock and Small Tortoise- 

 shell Butterflies answers perfectly, but the Cabbage 

 Whites and some others have reasons of their own for 

 taking a more or less horizontal position, or if placing 

 themselves vertically, keeping the head uppermost. 

 Here a second attachment becomes desirable, and 

 they secure themselves by a girdle passing round the 



