CABBAGE WHITE BUTTERFLIES 181 



as it proceeds from the spinneret, is caught by the 

 fore legs, and held taut, as by the fingers of a person 

 holding a skein of wool. When the girdle is com- 

 pleted the larva slips its head through, and is at once 

 adequately supported. 



In all three methods it is requisite that the girdle 

 should surround the body at a point well behind the 

 head. The tail is already fixed, so that the body 

 cannot be moved forward as a whole after the girdle 

 is completed, but by one or other of the three 

 methods described, viz. : (i) contracting the fore part 

 of the body during spinning ; (2) doubling it up ; (3) 

 arching it away from the fixed support, the girdle is 

 set far enough back, and a due amplitude is insured. 



When the pupa first becomes exposed, it is much 

 like the pupa liberated artificially from the larval 

 skin, and has in essentials the same external form as 

 the future Butterfly. The limbs and antennas and 

 proboscis are separate for a moment. Then they are 

 gently drawn over the breast, 1 the proboscis in the 

 middle line, and the others in perfectly regular pairs 

 outside it. A viscid fluid is poured out, which sets 

 on exposure to the air, and glues them fast. After 

 this the pupa can only move its abdominal segments, 

 and even this it rarely does, except when disturbed. 



During the pupal stage there are no outward signs 

 of life, although considerable internal changes are in 

 progress. The alimentary canal becomes smaller and 

 more complex ; a sucking stomach is partitioned off 

 from the larval crop, for use in drawing up nectar 



1 In some cases this appears to be effected directly by the 

 process of extrication. 



