78 



Table XX. — Thermal influence on development. 



Stage. 



Number 

 of obser 

 vations. 



Period. 



Average 



time for 



stage. 



Effective tempera- 

 ture. 



Average. Total 



Egg 



Larva . 



Pupa 



Entire develop 

 mental period . . 



107 

 36 



195 

 15 

 15 



161 



81 



305 



LOO 



185 



1902 



Sept. 4 to Oct. 3 



Oct. 7 to Nov. 13 



Nov. 24 to Dec. 15... 



Sept, 6 to Oct. 5 



Sept, 26 to Oct. 21.. _. 

 Nov. 11 to Dec. 12. . . 



July 6 to 31. 



Sept. 15 to Oct. 3 



Sept, 24 to Oct, 28.. . 



Nov. 2tol3... 



Dec.2to29 



Aug. 10 to Sept. 30.. 

 Sept. 16 to Oct. 15.... 

 Oct. 8 to Nov. 16 



1903, 



June 4 to July 15 



Aug. 20 to Sept. 28.. 



Davs. 

 3- 



4+ 

 11.0 



7.5 

 9.5 

 25.0 



3.5 

 5.2 

 6.0 

 7.6 

 14.5 



13.4 

 17.5 

 20.3 



18.3 

 19.0 



°F. 

 38.0 

 30.0 

 19.0 



35.7 

 30.6 

 19.5 



39.65 

 36.0 

 31.1 

 26.2 



18.5 



41.0 

 33.6 



32.0 

 33.1 



F. 



114.0 



120.0 



209. 



280.7 

 487.5 



138.8 

 187.2 

 186.6 

 199.1 

 268.2 



549.4 



.588.0 



585.6 

 628.9 



SUMMARY OF THE PRECEDING TABLE. 



Stage. 



Total 

 observa- 

 tions. 



Average 



period 



for 



Average | Total 

 effective effective 

 tempera- tempera- 

 ture ture. 



Egg-. - 



Larva 



Pupa 



Total development 



Observations on entire period 



52S 

 225 

 442 



Days. 

 3.75 



5.1 



F. 

 35.1 

 34.3 

 34.7 



F. 



141.6 

 301.8 

 177.0 



1,195 

 752 



17.65 

 17.7 



34.8 

 33.9 



614.2 

 600.0 



In studying the influence of temperature on development the figures 

 upon the separate stages serve best, as they give the widest range. In 

 each stage it may he seen that the maximum time is nearly, if not 

 quite, four times the minimum, while the average effective tempera- 

 ture difference is in the inverse order, hut about 2 to 1. In com- 

 paring the minimum and maximum, total effective temperatures, it 

 appears that when the average temperature is lowest the total heat 

 required to complete the development of the stage is nearly twice as 

 great as when the average temperature is highest. The length of the 

 developmental period is therefore not exactly inversely proportional 

 to the change in temperature. The retarding influence of decreasing 

 temperature appears to affect each of the immature stages in very 

 nearly the same degree. The total effective temperature required 

 forms a specific constant, which is fairly uniform for average effective 

 temperatures of between 30° and 40° F. These temperatures would, 

 during most seasons, prevail from June to October, inclusive. As the 

 average effective temperature falls below 25° F., however, there 

 results a great and disproportionate retardation in the development. 

 The reason for this difference may lie in the fact that when tempera- 



