174 ANIMAL BIOLOGY 



homeliness of people whom we come to like, it becomes 

 transformed upon closer acquaintance into a source of 

 positive pleasure. Hodge remarks, "I pick up a toad a 

 hundred times a season just to enjoy looking at its eye, 

 a living, sparkling, ever-changing jewel, and his music in 

 the springtime brings a pleasure that nothing else affords." 

 Toads are easily kept in confinement and make interesting 

 pets. 



The tree frogs (Hylidae) comprise an interesting family 

 of rather small frogs most of which live a large part of 



FiG. 139. A toad, Bufo halephilus. (From photo by Holliger.) 



their lives upon trees. The toes of most species are tipped 

 with sucker-like adhesive pads which enable them to climb 

 up vertical surfaces. The family in general is remarkable 

 for the extensive changes of color which take place in re- 

 sponse to the environment. Hyla versicolor is usually of 

 a bright green color when among green leaves, a dull gray 

 or brown when resting upon bark, and various interme- 

 diate shades under other conditions. This ability to change 

 color is to a considerable extent protective, and is affected 

 by light, temperature, rough or smooth contact, and a 

 variety of other agencies. Although not commonly seen 

 the tree frogs are very frequently heard, as the males are 



