244 ANIMAL LIFE 



surface-layers of the leaf on which it rests. On the 

 chlorophyll, starch, and other elements of this diet, 

 it rapidly grows and adds reserves of fat to accumulate 

 beyond its present needs. Moult follows moult with 

 increasing size, and the spines that project from its 

 surface find their office is assisting the process by 

 preventing the old skin from slipping back as it is 

 peeled off the new one. At the sixth moult a change 

 of form occurs. Knobs and ridges that had been 

 moulded under the skin now appear glued down on 

 to the head and thorax. In these projections we can 

 recognise the eyes, antennae, proboscis, legs, and wings 

 of the butterfly. When these appear the caterpillar 

 is full fed. Bearing the marks of the perfect insect, 

 it now assumes the shelter of a wall-coping or other 

 crevice, to the sides of which it proceeds to attach 

 itself by means of a silken hammock. To spin this 

 support, the larva emits a drop of liquid silk from its 

 mouth, bends its head back under its body, and works 

 from side to side fastening the thread at two points 

 opposite the middle of the body which thus lies in the 

 loop. The next process is the shedding of the last 

 larval skin, which is rolled off and forms the un- 

 sightly debris that we often find near a chrysalis. 

 The pupal skin is now exposed, and the ridges that 

 outline the appendages of the butterfly are conspicuous. 

 They are, however, but the outlines for which the 

 necessary detail of muscle, nerve, and blood-vessel 

 is yet wanting. On the surface all appears quiet 

 and rigid ; a wag of the tail is the limit of response. 



