'92 ANIMAL COLORATION. 



these naturalists to produce conclusive evidence that birds do 

 constantly pass over these larvas before the theory can be 

 regarded as firmly established. 



In the meantime the excessive fertility of the parent moths 

 appears to be a sufficient guarantee against extinction, apart 

 from any subsidiary advantage to be gained by colour pro- 

 tection. 



Some Evidence showing that Caterpillars are concealed by 

 Protective Coloration from Enemies. 



Mr. Poulton gives a few instances which tend to prove that 

 lizards do pass over and leave unnoticed protectively coloured 

 caterpillars. I may quote here an observation to the same 

 effect made by myself and Mr. Finn. A small green cater- 

 pillar (of one of the " Whites ") upon a nasturtium leaf was 

 put into a case with Lacerta viridis. The caterpillar was, so 

 far as could be judged by similar experiments, quite suitable 

 in point of size as food for the lizard, but it was certainly 

 entirely ignored. It must be mentioned, however, that the 

 caterpillar was absolutely motionless. 



Protective Coloration of the Iguana. 



Each instance of apparent colour resemblance must be dis- 

 cussed on its merits ; it is quite unphilosophical to assume 

 without further inquiry the general action of natural selection 

 in producing, or at least intensifying, the similarity of colour 

 between an animal and its usual environment. The onus 

 proba/idi lies with those who advocate the action of natural 

 selection. The usefulness of each case of colour resemblance 

 must be demonstrated ; and any facts which tend to prove 

 that it is of no particular use have far greater weight against 

 the theory than suggestions, merely based upon human ideas 

 of resemblance and difference, have in its favour. The green 



