395 



are shown in the upper right-hand corner of Fig. 18. For an ihust ration 

 of the conditions and correction processes for a summer period, see Figs, 

 r.) and 20. Note arrows indicating the equivalent of temperature 96°, 

 which is 83°. The alpha vaUies and substitution-quotients for the larger 

 groups of individuals were calculated by the methods indicated above, and 

 those for the smaller groups were interpolated. The substitution-quotient 

 as here derived is practically the same as one-twenty-fourth of the number 

 of developmental units for the stage. The alpha value varies with the 

 angle of the average daily march of temperature and humidity (Figs. 15 

 and 29). The substitution-quotients for the various determined alpha 

 values were derived from the temperatures thus corrected by the method 

 explained above. 



Fig. 20. Showing the velocity curve, alpha value and corrections for tem- 

 peratures for the weather data recorded on Fig. 19. 



For Glenn's 1915 data, this method gave 283 substitution-quotient 

 as the mean of the means of thirty-individual groups of pupae, beginning 

 April 13 and ending ]\Iay 19 (five aberrant individuals were omitted), and 

 a mean alpha value of 51.3° F. for the actually calculated cases. Mortality 

 was low. Of the 1,400 larvae tmder observation, about 1,054 pupated and 

 emerged. For the first generation, which began pupation June 19, and 

 ended August 7, the mean of the means was 266, and the mean alplia 

 value for all calculated cases was 50. G° F. The second generation, which 

 was taken as beginning with the pupation of an individual on August 8 

 and ending with the last emergence on September 9, consisted of 36 pupae 

 with a mean of 2-49. This was among the largest deviations from 270. 

 The mean alpha value was 50.8° F. 



