86 



EFFECT OF EXTERNAIi CONDITIONS. 



The influence of varying temperatures on the length of the pupal 

 stage is exceedingly interesting and instructive, the pupa being appar- 

 ently much more uniformly afl'ected than the other stages. This is 

 evident from the close agreement between the sums of elffectlve tem- 

 peratures given in the preceding table. 



On July 20, 1904, three recently formed pupse were placed in the 

 laboratory ice box and left there for thirt3^-five da3^s at a temperature 

 averaging about 57° F. They then showed no signs of emerging and 

 were removed to the temperature of the laboratory, where the moths 

 appeared after from five to eight days. They must have been develop- 

 ing slowly in the refrigerator, as the seven days during which they had 

 been at normal temperatures would not otherwise have been sufficient 

 for development. Calculations based on this experiment compared 

 with several other lots of pupse that developed at normal temperatures 

 show that development is apparently almost prevented by low tem- 

 peratures and suggests that the growth of the pupa is determined with 

 reference to a higher temperature than the 43° F. usual 1}^ chosen. 

 This is shown as follows: 



Table XXX.II1.— Effective tempei 



-atures for 



jnipal development 





Length of stage. 



Sums of eflfective temperatures. 



Above 43°. 



Above 58°. 



Above 60°. 



May 9 to 13 •- 



o 



662 



530 



724 



1,341 



o 



317 

 305 

 349 

 359 



o 

 271 



June 10 to 24 . 



275 



September 29 to October 23 



300 



Ice-box experiment 



308 







It will be noted that the sums are more nearly equal when 58° or 60° 

 are assumed to mark the inception of metabolic activity. 



During September, 1904, the influence of extreme cold was tried in 

 two cold-storage vaults at temperatures of 34°, 27°, and 18^, respec- 

 tivel}^ The results obtained are tabulated below: 



Table XXXIV. — Effect of low temperature on pup. r,. 





Larvae in cells. 



Pupse in loose earth. 



Temperature conditions. 



Total. 



Moths 

 emerged. 



Re- 



main- 



ed- 



live 



pupse. 



Mor- 

 tality. 



Total. 



Moths 

 emerged. 



Re- 



main- 



ed- 



live 



pupse. 



Mor- 





Per- 

 fect. 



De- 

 formed. 



Per- 

 fect. 



De- 



formed. 



tality. 



A. Placed at 34° for 48 

 hours 



19 

 23 



21 



4 

 4 



12 







1 







4 



1 



3 



Percent. 

 58 



74 

 29 



14 

 14 







1 

 









 







Percent. 

 79 



B. Placed at 34° for 24 

 hours, then at 27° 



100 



C. Placed at 34° for 24 

 hours, 27° for 24 

 hours, then 34° for 

 72 hours 



1 

 14 



100 











