COLOR AND PAITEUX IX ANIMATES 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 efTects of such gradatory or 

 light and shadow patterns among l)irds, and thus explains many 

 cases of bird patterns not ai)i)arently 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 zoc)- 

 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 resemblanc(>. Certnin 

 hares and other animals that live in northern latitudes are 

 wholly white during tlie winter wlien the snow covers every- 

 thing; but in summer, when nmch of the snow melts, reveahng 

 the brown and gray rocks and withered leaves, these creatures 

 change color, putting .on a grayish and brownish coat of h.-iir. 

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

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

 wholly v>iiite 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 ai)pearance 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 ])lumbeous and bluisii 

 from soil formed by decomposing bluish rock. Tlie same 

 variations in color are evident in the horncnl toads (Phnjuosotna), 

 as found on various colors of desert soils. 



On the campus of Stanford University there is a little jHMid 

 whose shores are covered in some places with bits of bluisli 

 rock, in other places with bits of reddish rock^ and in slill 



