60 THE BUTTERFLIES OF THE BRITISH ISLES. 



the others. The first ring seems to be without spines, but the 

 brownish head is set with short ones, two on the crown being 

 rather longer and blacker than the others, and are inclined 

 backwards. 



In the autumn, when still quite tiny, it constructs a winter 

 retreat (hibernaculum) (Plate 30) by fastening a growing leaf of 

 sallow to a twig with silken threads, and then, using more silk, it 

 draws the edges of the leaf together, and so forms a secure 

 chamber wherein it can rest until the following spring, when it 

 quits the domicile and sets to work on the tender foliage around 

 it. At this time the caterpillar is brownish in colour. The 

 chrysalis is of the remarkable shape shown on the plate. It is 

 brownish, with purplish or olive tinge ; behind the rounded hump 

 there is a patch of bright green, and above the wing-cases a 

 beautiful golden sheen. There are also other metallic spots and 

 dots on various parts. Altogether, it is one of the prettiest of 

 British butterfly chrysalids. 



I am tempted here to quote Buckler's excellent description 

 of the pupation of this species, as it will serve to show the 

 remarkable method by which caterpillars are able to perform a 

 seemingly impossible feat ; that is, to get absolutely free of the 

 old skin whilst hanging head downwards from the silken pad 

 or button to which they attach themselves by the anal claspers 

 when preparing to pupate. 



"When full fed the larva becomes rapidly paler, and then 

 suspends itself by the anal prolegs to a stem of the honey- 

 suckle or other surface, and hangs with its body downwards in 

 a sinuous curve, with its head bent a little upwards, facing the 

 abdomen ; it then remains motionless for three days, becoming 

 whitish on the abdomen, and remaining very pale green on the 

 thoracic segments. In the course of the third day the creature 

 seems to wake up, unbends its head, swings itself to and fro a 

 few times, then stretches itself downwards in a long attenuated 

 line, which causes a rupture of the skin close to the head ; 



