^4 BUTTERFLIES 



Coloration 



The caterpillars of butterflies and moths form a large 

 part of the food of insect-eating birds. These caterpillars 

 are especially adapted for such a purpose and in the econ- 

 omy of natin-e they play a very important part in keeping 

 alive the feathered tribes. During the long ages through 

 which both birds and insects have been developing side by 

 side, there have been many remarkable inter-relations es- 

 tablished which tend on the one hand to prevent the birds 

 from exterminating the insects and on the other to prevent 

 the insects from causing the birds to starve. The most 

 important of these, so far as the caterpillars are concerned, 

 are the various devices by which these insects protect 

 themselves from attack, by hiding away where birds are 

 not likely to find them, by clothing their bodies with 

 spiny hairs, by other methods of rendering themselves dis- 

 tasteful, or by various phases of conceahng coloration. 

 On the whole, the examples of the latter are not so numer- 

 ous or so easily found in the case of the larvae of butter- 

 flies as in those of moths. 



Perhaps the basal principle of concealing coloration is 

 the law of counter-shading, first partially announced by 

 Prof. E. B. Poulton, and later much more elaborately 

 worked out by Mr. Abbott H. Thayer, and discussed at 

 length by Mr. Gerald H. Thayer in his remarkable volume, 

 " Concealing Coloration in the Animal Kingdom." The 

 law of counter-shading is tersely stated in these words: 

 "Animals are painted by nature darkest on those parts 

 which tend to be most lighted by the sky's light and vice 

 versa." As this law works out on most animals that live 



