416 



The sum of developmental units for the period January 1 to April 

 13 in 1916 amounted to 4,992 (after multiplying each velocity value by 

 1.125 to bring the angle of the velocity curve to 45°). This divided by 

 34 gives 208 as the substitution-quotient, which is as near as can be 

 expected to the 197 for a first checking of the two methods. This differ- 

 ence is not surprising, for under treatment which did not differ, larvae 

 in one case pupated when put at 85° F. or other temperatures suitable 

 for pupation, as early as December 19, but in other cases did not pupate 

 until March. In general, February 1st seems too early for most larvae. 



Table XXV. Hihernated larvae at approximately constant temperature, 



191S (continued). 

 Air flow was 8 mm. per sec. for all cages. 



• Submerged. 



Townsend got pupation in November in a lot of 1923-24 larvae put in 

 suitable conditions. While they were in-door stocks, there appeared to 

 be no tangible reason for this early pupation. Obviously, winter phe- 

 nomena are not understood ; and, until they are, over-wintering probably 

 can not be put on a scientific basis. 



Prediction of the First Pupation of Hibernating Larvae. Our experience 

 with the larvae of the codling moth leads to the conclusion that hibernation is 

 concerned with two physiological conditions: (1) the true dormant period, 

 and (2) the "pre-pupal" period, not as yet distinguishable from the dormant 

 period, but concerned with the changes which lead to pupation. Late autumn 



