374 Eelatiok of Water to the Behatioe of 



their emergence, so that now, in case other conditions were suitable, they were 

 ready to enter upon their reproductive activities. Below 13° to 15° C. in soil- 

 temperature the water-relation was not the controlling factor, but the duration 

 of the hibernating period depended upon the length of the dry season in an arid 

 complex and upon the length of winter (low temperature) in a temperate 

 region. 



Baumberger (1914) reviews, at length, the literature on hibernation of insects 

 and reaches the following conclusions, chiefly from his own researches : 



" 1. That temperature is but a single factor and not necessarily the con- 

 trolling one in hibernation. 



" 2. That hibernation is usually concomitant with overfeeding and may be 

 the result of that condition or the result of accumulation of inactive substances 

 in the cytoplasm of the cell due to feeding on innutritive food. 



" 3. That the loss of water which is general in hibernation probably results 

 in a discharge of insoluable alveolar cytoplasmic structures which have accumu- 

 lated and produced premature senility with an accompanying lowering the rate 

 of metabolic processes. 



"4. That starvation during hibernation, together with loss of water, may 

 result in rejuvenation, when aided by histolysis, and an increase in permeability. 



" 5. That this rejuvenated condition and increased permeability will, if 

 stimulated to activity by heat, permit pupation in codling-moth larvae, which 

 in this case is the termination of the hibernating conditions." 



The results of Sanderson and Peairs (1913) add another condition for 

 hibernation that was also discovered by Tower (1906) for the potato-beetle; 

 this is the influence of heredity. The former authors reached the following 

 conclusions : 



" That our first work was an effort to show that emergence from hibernation 

 was due to an accumulation of temperature, but it soon became apparent that 

 hibernation is very largely controlled by the influence of heredity, and that the 

 relation of the temperature and inheritance must be determined for each 

 species." 



For the Mexican cotton boll weevil. Hunter and Hinds (1904) found that 

 dryness was more desirable for hibernation and that mortality during hiberna- 

 tion was greater from exposure to moisture than from cold; but, on the other 

 hand, high temperatures and moisture were the best conditions for the develop- 

 ment of such beetle larvse. In this connection, Baumberger (1914) stated: 



" The effects of ether on plants is similar to hibernation and since the action 

 of ether is probably a drying one, this may throw light on the importance of 

 moisture in hibernation." 



Loeb (1906) says: 



" The lack of water acts similarly to a low temperature. This is the reason 

 why seeds can be kept aUve so long. Lack of water may reduce the reaction 

 velocity of the hydrolytic processes in seeds at ordinary temperature so con- 

 siderably that it may become practically zero." 



The snail, according to the results of Kiihn (1914) loses weight in winter 

 and reacts to drought in summer. Unless it contains a large amount of water, 

 no dry food is taken, and if placed under moist conditions when in hibernation 

 it will come out of its closed shell. Bellion (1909) finds that a low moisture- 

 content of the air is the determining hibernating factor in the European snail, 



