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The University Science Bulletin. 



of temperatures. These facts are of importance to scientists who 

 wish to ascertain the exact relations between temperature and 

 development, but for practical purposes these slight variations 

 need not be taken into consideration, especially when the varying 

 out-of-door temperatures are to be used as a basis of study. 



The problem, therefore, dealt with in this paper may be stated 

 as follows: Given the length in days of the period of development 

 at different average daily temperatures, and the average daily 

 temperatures for each of the periods, to find the threshold of de- 

 velopment, the degree of the maximum rate of development, the 

 temperature constant, the effects of temperatures above the de- 

 gree of the maximum rate of development, and how to make cor- 

 rections in the temperature factor when the temperature for a part 

 of the time during the period was above the degree of the maximum 

 rate of development. 



The problem is a simple one when constant temperatures are 

 used, but with widely varying daily temperatures as a base for 

 study the problem is more difficult, since the average daily temper- 

 atures for the periods must be used and in nearly all observations 

 these are influenced by temperatures below the threshold of develop- 

 ment or temperatures above the degree of the maximum rate of 

 development. 



In this paper the method of procedure will be illustrated by studies 

 on the pupal period of the Carpocapsa pomonella, based on observa- 

 tions out of doors on the pupal period of 3,817 pupae at mean daily 

 temperatures varying from 52.6° F. to 82.6° F. 



The following table gives the complete results of the study : 



