BEHAVIOR AND COLOR CHANGES OF TREE FROGS 55 



corner of my cellar and observed from time to time. Very 

 soon after this change they showed signs of dormancy, crept, 

 or rather backed, for the mode of burrowing seems to be by 

 means of the hind feet and the sharp posterior end of the body 

 working together. In this way they burrow and bury them- 

 selves. My specimens burrowed backward under the moss and 

 debris of the cage, crouched with head close to the bottom, 

 closed the eyes and literally went to sleep. They were left for 

 some time and in March I carefully inspected the box and 

 found that a very small specimen had died. The others 

 seemed normal. They appeared very sluggish, yet when turned 

 over they righted themselves and resumed the sleeping attitude. 

 Toward last of March they were again inspected, and to my 

 great surprise and regret all were dead. Whether the hibernat- 

 ing conditions had proven unsatisfactory, or whether the inspec- 

 tion and handling to which they had earlier been subjected, 

 was the occasion of the untoward ending one may only surmise. 

 Perhaps something of both may have been involved. 



Hibernation in a state of nature I have not studied. In one 

 case I was fortunate in finding a specimen which was apparently 

 just emerging from its winter sleep. It was found in the woods 

 and very near where at the same time I found a specimen of 

 the wood frog which had not yet emerged, but seemed in pro- 

 cess of emergence, as the specimen was dug out from a bank 

 of earth and leaves, and not yet sufficiently active to make 

 any efforts to escape. In late autumn I have also found speci- 

 mens on the ground along a wood path, and conditions of tem- 

 perature were such as to suggest the presumption that they 

 were even then seeking suitable hibernating quarters. 



COLOR CHANGES 

 The general facts of color changes as a feature in the behavior 

 of amphibia have been long known. Of course, tree frogs as 

 affording some of the best illustrations of this phenomenon are 

 no exception to this matter. In fact the European species, 

 H. arbor ea, has been most critically studied of any, and has per- 

 haps afforded the larger mass of existing knowledge on the subject. 

 As will be seen in a later connection, some of the more striking 

 aspects of behavior in color change have been studied in this 

 species. So far as I am aware no one has made any of the 



