METAMORPHOSIS OF LARVA 9 



versely over its body, the ends on either side 

 being attached to the wall. This done, there 

 is again a period of inactivity during which 

 the anterior segments behind the head are 

 seen to thicken and swell out. 



The first sign that the metamorphosis is 

 about to take place (the change is effected in 

 a few minutes) is the splitting of the skin on 

 the top of the enlarged segments. As the spUt 

 opens out, the larval skin falls away and 

 shrivels at the sides. At this juncture the 

 process is somewhat impeded by the silken 

 ligature already described ; but the creature 

 is equal to the occasion. With spasmodic con- 

 tortions of the body it succeeds in freeing 

 itself of the slough which, still in a piece, is 

 worked down to the anal claspers which, in 

 their turn, are shed with it. But at this 

 critical moment the caterpillar exerts a final 

 effort, hooking its tail into the pad by means 

 of minute hooks which have taken the place 

 of the cast-off claspers. Thus what once was 

 a cylindrical body clinging by legs to a wall 

 is now fusiform, legless and helpless, though 

 perfectly secure save for outside interference. 



The Cabbage-White is known as a double- 

 brooded species ; which means that during a 

 favourable season there will be a succession of 

 broods, two or more, who quickly pass through 



