HIBERNATION IN THE POTATO BEETLE. 



391 



20 per cent, respectively. When the beetles burrowed in the 

 ground the water content averaged 56 per cent, and the fat 

 content 29 per cent. The results of these experiments indicate 

 quite clearly that a loss of 20 per cent, in the water content and 

 a gain of slightly over 20 per cent, in the fat content took place. 

 Tower (24) obtained with this species a reduction of 27 per cent, 

 in the water content. With hibernating grasshoppers Bodine (4) 

 found a reduction of 13 per cent. 



75 



5 



60 



<u 



Q- 



15 







Preparing for 

 hibernation 



Hibernating 

 days 



60 150 



Recovery 



from 

 hibernation 



After hibernation 

 Days 



6 14 30 



60 



FIG. 4. Ordinates show the percentage of water and fat content of potato 

 beetles, before, during and after hibernation. Note the reduction in the water 

 content and increase in fat content as the beetles enter hibernation, and the ex- 

 tensive depletion in fat during the first few months as compared to the remaining 

 period of hibernation. 



The view commonly held is that a diminished water content 

 makes protoplasm able to withstand extremes of temperatures. 

 With potato beetles this does not appear to be valid, since 

 invariably they must burrow in the ground to a considerable 

 depth (10-18 inches) presumably to successfully escape extremes 

 of temperatures. Experimentally the influence of greater vari- 

 ations in temperatures was determined by permitting only several 

 inches of soil to intervene between the dormant beetles and the 

 outside air. The results of such treatment upon hibernating 



