202 DAYS OUT OF DOORS. 



ceedingly active, particularly if hungry, and made no 

 effort to avoid the direct rays of the sun. 



When exposed to a sudden transition from a very high 

 to a low temperature, they quickly became inert, and, as 

 the warmth was allowed to increase, it was instructive to 

 see the sluggish movements of both the lizards and the 

 imprisoned flies give way to more active ones, which culmi- 

 nated in the restored suppleness of the reptiles being equal 

 to the capture of the swiftly darting insects. Forced ex- 

 posure, for a period of three hours, to a temperature of 

 135 caused death in four instances, and brought about a 

 condition akin to aestivation in nine specimens thus ex- 

 posed. As the pine-tree lizards are always found in local- 

 ities where there is adequate shelter from excessively 

 high temperature, it is not probable that aestivation ever 

 occurs, as it does occasionally among some of our wild 

 mice ; but it is interesting to note that a condition closely 

 allied to it can be artificially produced. 



The conclusion reached by both field observation and 

 experiments was, in brief, that when the temperature is 

 such that those forms of insect life upon which they de- 

 pend become inactive, the lizards withdraw to their shel- 

 ters and likewise remain quiet if not asleep, this period of 

 inactivity extending over several days, as during the prev- 

 alence of a northeast storm, or a protracted " spell " of 

 cool and cloudy weather. Again, experiments with a large 

 number in confinement showed that when kept without 

 food at a low temperature, they live for many days, while 

 a like number starved in a short time when a high tem- 

 perature was maintained. This lizard, therefore, appears 

 to be one originally belonging to a tropical climate that 

 has gradually become adapted to a temperate and variable 

 one. 



The normal coloring of the pine-tree lizard is distinctly 

 protective. Whether this has been gradually acquired or 



