ADJUSTMENT OF ORGAXISMS TO ENVIRONMENT 427 



A few animals have the power to alter their coloration to 

 match their environment. The common tree frog is one such. 

 The specimen shown in figure, (fig. 249) was of a perfect 

 gray color while it sat on the button bush stem, and a short 

 time after being transferred to the leaves, it was equally 

 inconspicuous by reason of its beautiful green color. 



Fig. 250. A dragonfly {JEschna constricta) . 



Flash colors. — There is a class of conspicuous markings 

 upon the bodies of animals that is not for continuous exhibi- 

 tion, and concerning the function of which the greatest 

 diversity of opinion has been held. Since these are usually 

 exposed intermittently in flight, we may use the non-com- 

 mittal name of flash colors for them. Such are the white 



