COLORATION 87 



cally all value at the very moment when In theory it ought 

 to be of most use. 



Moreover, the so-called "countershading" in very many 

 animals is not concealing at all, but advertising. Very light 

 hues on the under part of a bird or mammal, even although 

 the upper part is dark brown or black, may technically be 

 called instances of countershading, but they certainly have 

 not the slightest concealing value. A black squirrel is well- 

 nigh as conspicuously colored as possible; but when he has 

 an orange belly or even a mere white belly the addition of 

 another vivid color does not tend to conceal him. We here 

 speak of our personal experiences in the woods of the South- 

 ern States, where the black and orange bellied or white bellied 

 fox-squirrels are always conspicuous in their native haunts ; 

 and of our personal experience on Buckskin Mountain, 

 Arizona, where the big black squirrel with a white tail is 

 of diurnal habits and is always conspicuous — its coloration 

 being of a highly advertising value. There are very ex- 

 ceptional circumstances under which the white belly of a 

 white-tail deer or a white-footed mouse or a weasel may be 

 concealing; but they are so exceptional that they can be 

 disregarded; ordinarily, when it can be seen at all (which 

 on the weasel is almost never, and as regards the mice 

 very rarely) it has a slight advertising value. When one 

 can see the white of an impalla or sable it is usually adver- 

 tising. Herons with white bellies are no more concealed 

 than those of solid colors. 



Finally, there are many animals with no countershading, 

 living under conditions precisely like those surrounding the 

 countershaded kinds; and yet no effect one way or the 

 other is produced by this difference. The weasel family, a 



