308 THE SCHOOL OF RJ^AUMUR 



tail larva, which, as he remarks, emit a disagreeable 

 odour. He did not suspect that the Puss-moth larva 

 possesses a very similar organ behind the head. 



The young larva, he tells us, is uniformly dark, but 

 at each change of skin the colour becomes modified, until 

 a leaf-green surface, diversified with streaks and patches 

 of other shades, is obtained. Male larvae are usually 

 distinguished in their last stage by rose-coloured patches 

 on the hump, the seventh segment, and elsewhere. The 

 larvae are very sluggish, and move about as little as 

 possible. 



In our own generation the most remarkable peculiar- 

 ities of the Puss-moth larva have been interpreted as 

 defensive structures ; it escapes notice by its general 

 protective resemblance to the food-plant, and deters its 

 enemies by its terrifying appearance and attitude, as 

 well as by its power of ejecting an irritating fluid. 

 All these points have been worked out by Prof. Poulton ; 

 I will not weaken by abridgement his interesting dis- 

 cussion, which is readily accessible to every naturalist.^ 



The irritating fluid, shot out from the slit behind the 

 head, has been chemically examined by Poulton, who 

 finds that it is a strong solution of formic acid, the 

 same acid which constitutes the poison of ants and of 

 the stinging-nettle. 



In order to soften the wooden cocoon, the moth 

 emits from its mouth an alkaline liquid, which contains 

 between one and two per cent, of caustic potash ; it 

 uses part of the pupal skin as a shield which it can 

 press against the softened shell of the cocoon, without 

 risk of injury from the corrosive liquid. ^ 



An expansion of knowledge similar to that which has 



* Poulton, Colours of Animals ^ chap. xiv. 



2 Latter, Trans. Entom. Soc, 1892, pp. 287-292; 1895, pp. 399-412. 



