294 THE PAPILIONINA^ OR BUTTERFLIES. 



are therefore under the necessity of constructing a 

 sort of ladder of silk by moving their heads from side 

 to side^ and thus stretching a series of short lines 

 between the extreme points which they can reach with 

 their spinnerets. Even with this precaution, how- 

 ever, they often fall to the ground, and from the 

 number of ladders that may be seen running half- 

 way up a window, it is probable that after two or three 

 unsuccessful attempts the caterpillars may seek some 

 other means of attaining their object. 



The change to the pupa state is effected in the fol- 

 lowing manner. The insect having selected a spot 

 in which to pass its period of repose, first of all spins 

 a few loops of silk, to which it attaches itself by the 

 hooks existing on the anal prolegs. It then forms a 

 loop across the middle of its body, by which this is 

 supported, frequently in an upright position. A short 

 period of rest ensues, after which the skin of the back 

 bursts near the head, and the back of the pupa makes 

 its appearance in the opening. The skin is then gra- 

 dually pushed backwards by the wriggling of the 

 insect until it forms a wrinkled mass about the tail 

 of the pupa, which then appears much shorter than 

 the caterpillar from which it has been produced, of a 

 whitish colour, adorned with numerous black points, 

 and exhibiting some curious angular projections, espe- 

 cially towards the anterior extremity. The next busi- 

 ness is to get rid of the crumpled skin of the cater- 

 pillar, and this is effected in a singular manner. The 

 pupa, which at this time is soft and capable of con- 

 siderable movement, draws its tail out of the remains of | 

 its old integument and attaches it, by means of some 

 hooks with which it is furnished, to another part of 

 the little tuft of silky loops formed for this purpose. 



