Color and Form, 133 



ered leaves among which she places her nest, that 

 the keenest eye seldom discovers her. Though one 

 of the wildest of birds, she settles herself upon the 

 nest and seems to trust in the deceiving power of 

 her feathers, and so remains quiet until the foot of 

 the intruder is almost upon her. 



The Ptarmigan Grouse of Greenland and the 

 Sage-hen of our Rocky Mountains are both beauti- 

 ful examples of what the united action of color and 

 Instinct can do to protect the bird. I have fre- 

 quently seen both of these birds light, and yet have 

 been entirely unable to distinguish them from the 

 surrounding vegetation until some movement of 

 the bird aided the eye. There is also change of 

 color from summer to winter and the instincts of 

 the animal are in harmony with these changes for 

 its welfare. 



But it is among insects that this correlation 

 between form and color and Instinct, is most readi- 

 ly observed and most wonderful. There are insects 

 that simulate leaves so closely that they deceive 

 careful observers. Mr. Wallace gives an interesting 

 account* of insects that imitate, in their structure 

 and color, decaying and diseased leaves. And In- 

 stinct here aids in the work of deception ; for these 

 insects fasten themselves upon limbs in such places 

 and in such positions as withered leaves would nat- 

 urally be found in. A spidert is also found, accord- 

 ing to the same author, that resembles a bud in 

 appearance, and his natural place of concealment is 



Natural Selection," pp. 59-61. t ^' P- ^9. 



