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INFLUENCE OF TEMPERATURE OX BIOLOGICAL SYSTEMS 



There is another unexpected feature to the alternating temperature ex- 

 periments, namely that the weight losses at average incubation tempera- 

 tures of 15° and 17° are not as great as those at constant incubation 

 temperatures of 15° and 17° (table 2). Correlated with this lower weight 

 loss there is good hatching (86% and 88%) and high vitality (60% and 

 78% survival). One way to summarize the differences in effects of constant 



Table 4. Percentage successful growth of oncopeltus larvae 

 following incubation under various conditions 



1 Data from 50% R. H. taken from Hodson and Al Rawy (5). 



2 Av. 17° produced by 4 hr. at 25° + 20 hr. at 15° daily. 



' Av. 16.4° produced by 2},i days at 25°, then \9}i days at 14°, then 2^ days at 

 25°. Similar to line I of fig. 5. Included to show necessity of frequent warming. (From 

 ref. 8.) 



4 Av. 15° produced by 2 hr. at 25° + 22 hr. at 14° daily. 



5 Av. 15° produced by 4 hr. at 25° + 20 hr. at 13° daily. 



« Av. 14° produced by 4 hr. at 20° + 20 hr. at 13° daily. (From ref. 8.) 

 ^ Av. 14° produced by 2 hr. at 25° + 22 hr. at 13° daily.' (From ref. 8.) 



versus alternating temperatures is to say that the 'day-degree' calculation 

 works satisfactorily for predicting the time of hatching under either con- 

 stant or varying temperature conditions, but that the 'calorie-counter' 

 calculation works satisfactorily for predicting weight losses only under 

 constant incubation temperatures, and that neither at the present stage of 

 investigation permits predicting viability.^ 



^It is of considerable ecological interest that developing Oncopeltus fare much 

 better under varying temperature conditions than under a constant temperature which 

 is equal to the average temperature of the varying set. It would seem both premature 

 and out of place, however, to expand on this subject here. 



