78 



Table XX. — Thermal influence on development. 



Stage. 



Egg. 



Larva . 



Pupa . 



Entire develop- 

 mental period . . 



Number 

 of obser- 

 vations 



885 

 107 

 36 



195 

 15 

 15 



161 



81 

 167 

 29 



4 



96 



;i<)5 



66 



185 



Period. 



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... 



July6to31 



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.. 



Average 

 time for 



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 



Effective tempera- 

 ture. 



Average. Total. 



:«.o 



30. (I 

 19.0 



35.7 

 30.6 

 19.5 



39. &5 



:^.o 



31.1 

 26.2 



18.5 



41.0 

 3:16 

 29.5 



32.0 



as.i 



'F. 

 114.0 

 120.0 

 209.0 



267.7 

 280.7 



487.5 



138.8 

 187.2 

 186.6 

 199.1 

 268.2 



549.4 

 588.0 

 598.8 



585.6 

 628.9 



SUMMARY OF THE PRECEDING TABLE. 



Total 

 observa- 

 tions. 



Average 



period 



for 



Average 

 effective 

 tempera- 

 ture 



Total 

 effective 

 temi)era- 



ture. 



Egg... 

 Larva 

 Pupa.. 



528 

 225 

 442 



Days. 

 3.75 

 8.8 

 5.1 



'F. 

 35.1 

 34.3 

 34.7 



°F. 

 141.6 

 301.8 

 177.0 



Total development 



Observations on entire period 



l,ia5 

 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 be seen that the maximum time is nearly, if not 

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

 ture difl'erence is in the inverse order, but 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 temj)erature 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- 



