PROTECTIVE RESEMBLANCE 133 



which feed upon grasses or the needle-like leaves of pine 

 trees are commonly marked longitudinally with strongly 

 contrasted colours. Those of the pine beauty moth 

 (Panolis piniperda), for example, are striped with white 

 and dark green, and fit their environment so perfectly 

 that even an expert naturalist, with a full knowledge of 

 what he is looking for, rarely discovers a specimen except 

 by chance. 



The colours of an insect often appear conspicuous 

 when the creature is isolated from its customary surround- 

 ings ; yet they probably blend perfectly with the particular 

 setting in which Nature intended them to be seen. Thus, 

 the large caterpillar of the privet hawk-moth (Sphinx 

 Ugustri) is bright green, with seven oblique white stripes 

 bordered with purple on each side. If we see it for the 

 first time in a cardboard box, the protective value of its 

 coloration is incomprehensible. But the same cater- 

 pillar, when among the leaves of privet or lilac, is wonder- 

 fully concealed. Professor Poulton has pointed out that 

 the purple-margined white stripes break up the surface 

 of the caterpillar, and perhaps suggest the appearance of 

 leaf shadows. 



Protective colouring in nature is often enhanced by a 

 subtle rendering of light and shade — a fact which has 

 been emphasized by the American artist-naturalist, Mr. 

 Abbott H. Thayer. The presence of an animal, even if 

 its tints accord perfectly with the background, may be 

 betrayed to its enemies by the sharpness of its outline, or 

 by the shadow which it casts. Mr. Thayer reminds us 

 that an artist, by the process of shading — i.e. painting in 

 shadow — produces the appearance of relief, or solidity, 

 upon his flat canvas ; and he claims that Nature's pro- 

 tective colouring tends to promote an exactly opposite 

 effect. Her shading aims at what we may term a paint- 



