COLOR AND PATTERN IN ANIMALS 407 



by a color and pattern not directly imitative of the immediate 

 environmental objects, but of such a kind as to be lost among 

 the light and shadow gradations produced by light shining 

 through leaves, twigs, etc. Thayer has very interestingly 

 shown the possibilities and actual effects of such gradatory or 

 light and shadow patterns among birds, and thus explains many 

 cases of bird patterns not apparently very closely imitative, 

 but nevertheless very effective in making the bird indistin- 

 guishable when at rest on its nest or in the bushes or grass 

 of its usual habitat. General protective resemblance is un- 

 doubtedly very widespread among animals, and is not easily 

 appreciated when the animal is seen in museums or zoo- 

 logical gardens that is, away from its natural or normal en- 

 vironment. 



A modification of general color resemblance found in many 

 animals, may be called variable protective resemblance. Certain 

 hares and other animals that live in northern latitudes are 

 wholly white during the winter when the snow covers every- 

 thing; but in summer, when much of the snow melts, revealing 

 the brown and gray rocks and withered leaves, these creatures 

 change color, putting on a grayish and brownish coat of hair. 

 The ptarmigan of the Rocky Mountains (one of the grouse), 

 which lives on the snow and rocks of the high peaks, is almost 

 wholly white in winter ; but in summer, when most of the snow 

 is melted, its plumage is chiefly brown. Locusts of various 

 species of the genus Trimerotropis show a variability in color 

 of individuals, ranging through gray, brown, reddish, plumbeous 

 and bluish, and such accompanying variability in marking as 

 to result in producing much variety of appearance in a single 

 series of collected individuals. We have noted in collecting 

 these locusts in Colorado and California that this variability 

 of coloration is directly associated with color differences in the 

 soil of the localities in which these locusts live; the reddish 

 individuals are taken from spots where the soil is reddish, the 

 grayish, where it is sand-colored, and the plumbeous and bluish 

 from soil formed by decomposing bluish rock. The same 

 variations in color are evident in the horned toads (Phrynosoma) , 

 as found on various colors of desert soils. 



On the campus of Stanford University there is a little pond 

 whose shores are covered in some places with bits of bluish 

 rock, in other places with bits of reddish rock, and in still 



