COCOON OF PUSS-MOTH 15 



When full fed, on either sallow or poplar, 

 the larva begins to lose its bright colouring, 

 which is a certain sign that the change is about 

 to be made. This applies to all lepidopterous 

 larvse. Leaving the foliage, the caterpillar 

 follows along the branch to its junction with 

 the stem of the tree, and so crawls downwards. 

 When the poplar is slender and not suitable to 

 requirements, it proceeds over the ground to 

 another spot ; but if the trunk of the original 

 tree is large and the bark rough and uneven, 

 there is no need to go further. Selecting a 

 cavity amidst the excoriations of the bark, 

 the creature proceeds to fashion the hollow to 

 take the form of its body ; this it does by 

 means of its powerful mandibles. After the 

 cavity has been duly rounded off and smoothed 

 down, the larva commences to spin a roof, at 

 the same time chipping off bits of bark which 

 amalgamate with the viscous thread as it 

 issues from the spinnerets. By degrees the 

 roof under construction becomes more and 

 more opaque until the worker is no longer 

 visible ; the work, however, continues, for 

 this shell-Uke protection must be rendered 

 air-tight and waterproof and of such a con- 

 sistency that nothing may penetrate. As a 

 matter of fact, this cocoon is as hard as 

 cement, and being formed chiefly from the 



