Fi(i. 56. Two artificial buttei-flics, one dusky and one light, seen against a dusky tree- 

 trunk; the light one conspicuous, the dusky one barely distinguishable. 



Fig. 57. The same two artificial butterflies seen against a light background, the dusky one con- 

 spicuous, the light oneharely distinguishable. 



These two pictures show that no one color will conceal an animal that must move across the varied.and varying face of nature. 



In our pictures of artificial models we have purposely ignored the factor of interposed vegetation, which in nature plays so large 

 a part in abetting 'vanishment' by obliterative costumes. For we are here studying main principles, divested as far as possible of 

 accessories. 



