HIBERNATION IN THE POTATO BEETLE. 395 



hibernation, based upon observing adipose tissue loaded with 

 urate crystals before hibernation, must be regarded as signifying 

 that it serves the purpose of an excretory organ. 



There appears no valid reason for assigning to the fat body a 

 urinary function. In the hibernating animal the metabolic 

 activity of most cells is reduced to a minimum, and in the fat 

 cells, judging from the respiratory quotient, it is most active. 

 Hence the cells become charged with an accumulation of albu- 

 minoid granules and other products. The urates found in these 

 cells are not an indication of their special urinary function, but 

 of a more active metabolism at a period which serves the animal 

 best. This may occur before or during metamorphosis, or 

 throughout the progress of hibernation. 



THE METABOLISM OF ACTIVE, STARVING AND 

 HIBERNATING BEETLES. 



A knowledge of the respiratory metabolism of active, starving 

 and hibernating beetles seemed desirable for comparing the 

 chemical changes involved. Of singular interest are the anal- 

 ogous rates of COo output procured from beetles emerging from 

 hibernation and pupation (Figs. 8-9), indicating, perhaps, a 

 condition of physiological youngness or purification (Roubaud) 

 as a result of hibernation. Bodine (4) found hibernating grass- 

 hoppers produced a higher rate of COo output than growing 

 animals kept at the same temperature, suggesting he states, 

 "that animals remain young throughout the period of hiberna- 

 tion." The CO 2 output of potato beetles throughout the progress 

 of hibernation invariably indicates a reduced metabolic activity, 

 in some respects comparable with that of starving animals 

 (Fig. 9). Indeed, there appears to be a parallelism in respiratory 

 metabolism between starving and hibernating forms. In the 

 former, however, the velocity of reaction of the life processes- 

 continues to function most actively and reserve substances are 

 rapidly depleted, a condition eventually leading to the death of 

 the animal. In the latter most of the life activities are con- 

 siderably depressed and nutrient material is, therefore, used 

 sparingly. 



With older beetles, the metabolic activities are also extremely 

 reduced, but not to the extent met with in hibernating or starving 



