WATER RELATIONS IN HIBERNATION. 23! 



position. All experiments were in cages six feet square and 

 three feet high, with wooden or cement bases that extended into 

 the ground two and one half feet, or below the depth to which 

 the animals burrowed in hibernation. These cages were covered 

 with sixteen mesh pearl wire cloth, which acted to soften the 

 rigors of the desert environment, especially the temperature, 

 rate of evaporation and wind flow, so that the materials while 

 subjected to the rigors of the desert did not receive the whole 

 intensity thereof, but approximately the average conditions. 



Throughout the food has been the cultivated potato, as in 

 the original habitat of the materials. All watering was by 

 irrigation about the roots of the plants, and in all respects care 

 was taken to prevent the experiments from having any other 

 than the desert environment about them. 



Caged experiments were used instead of isolated locations in 

 the open for two reasons: first, observation and record, as well 

 as protection, could best be maintained in the location and in 

 the arrangements as devised; and second, in caged experiments- 

 all selective action by animals that might use these beetles as 

 food was eliminated and the results would, as fully as possible,, 

 be those directly due to the physical environmental complex. 

 It developed in the course of the experiments that the arrange- 

 ments provided not only eliminated this source of complication, 

 but that predaceous enemies, parasites, and epidemics were 

 also absent, no trace of any of them having been discovered, 

 so that as far as I am able to discover, the results are solely the 

 product of the action of the physical environment upon the 



introduced animals. 



THE EXPERIMENTS. 



All materials were introduced at the opening of the summer 

 rains, and taken directly from hibernation to Tucson and intro- 

 duced into the cages, there giving two generations in rapid 

 succession, the second going into hibernation late in the summer, 

 depending upon the environic condition. The following series 

 have given the data for this paper: 

 T 99, introduced 1908, now in hibernation FIS. 

 T 100, introduced 1909, carried to Fi2 and lost in making repairs. 

 T 100 A, introduced 1911, now in hibernation in Fi 2 . 



