COLOR IN ANIMALS 149 



rabbits, all of which markings are invisible when the ani- 

 mals crouch. Some of the desert lizards are conspicuously 

 banded on the under surface of the tail, which they elevate 

 and arch over the back when startled, running with great 

 rapidity for a short distance, then suddenly crouching, until 

 only the protectively colored back is visible, or rather in- 

 visible, among the rocks and sand. 



These animals, which show such confusing coloration, 

 generally run or fly in an irregular course, and just before 

 they come to rest they cover the conspicuous color and fre- 

 quently dodge to one side, so that they lie unnoticed at some 

 distance to one side of the spot where they were last seen 

 by the observer. 



It is of course possible that in many cases the same 

 markings may serve the double purpose of recognition marks 

 or signals and of increasing the startling effect of the sudden 

 disappearance of their possessors when they come to rest. 



Sexual coloration. 



\Ye have already had occasion, in connection with the 

 discussion of sexual selection, to refer to the differences in 

 the appearance of the males and the females of many species. 

 These differences are often lar^elv differences in color, and 



d> j 



should be mentioned in any treatment of the phenomena of 

 color in animals. The use of these sexual colors is, 

 apparently, to render the male attractive to the female and 

 secure her as his mate. In our discussion of sexual selection 

 we said that these brilliant colors of the male are seen 

 among birds, lizards, fishes, spiders, in many species of 

 butterflies, and in some insects. \Ve will stop here to men- 

 tion but a few instances from these groups. Among birds 



