98 



would be limited to about 250,000 weevils per acre. The possibility 

 that the progeny of one weevil will amount to 12,000,000 in the course 

 of a season would therefore rarely if ever be realized. 



THERMAL. INFLUENCE UPON ACTIVITY AND DEVELOPMENT. 



The influence of temperature has been frequently mentioned as an 

 important point, but it may be more clearly understood by collecting 

 some of the most important observations relating to it. A study of 

 this subject throws much light upon such questions as seasonal and 

 daily activity, the rapidity of development at various seasons, hiber- 

 nation, and the time of emergence from hibernation. The influence 

 upon development will be first considered. For a portion of these 

 observations an ice box was especially designed and constructed to 

 facilitate observations at low and constant temperatures. (See 

 PL XVI, fig. TO.) 



Table XXIII. — Thermal influence on development. 



Stage, 



Egg 



Larva 



Pupa 



Number 

 of obser- 

 vations. 



Entire develop- 

 mental period. 



3S5 

 107 



195 

 15 



15 



161 

 81 



167 



29 



4 



96 



305 

 66 



Period. 



1901 



1902. 



Sept. 4 to Oct. 3 



Oct. 7 to Nov. 13 



Nov. 24 to Dec. 15 .... 

 Ice-box experiments, 



Sept. 6 to Oct. 5 



Sept. 26 to Oct. 21 



Nov. 11 to Dec. 12 



Ice-box experiments, 1904 



Julv 6 to 31 



Sept. 15 to Oct. 3 



Sept. 24 to Oct. 28 



Nov. 2 to 13 



Dec. 2 to 29 



Ice-box experiments, 1904 



Aug. 10 to Sept. 30. 

 Sept. 16 to Oct. 15 . 

 Oct. 8 to Nov. 16... 



100 June! to Julv 15 .. 

 185 | Aug. 20 to Sept. 28. 

 135 In ice box, 1904 



Average 

 time for 

 stage. 



Effective tempera- 

 ture. 



Average. Total. 



Da us 



11.0 

 5.1 



9.5 



25.0 

 12.5 



3.5 

 5.2 

 6.0 



13. 4 

 17.5 



20.3 



18.3 

 19.0 

 30.0 



°F. 

 38.0 

 30.0 

 19.0 

 27.0 



35.7 

 30.6 

 19.5 

 27.0 



39.65 



36.0 



31.1 



26.2 

 18.5 

 27.0 



41.0 

 33. 6 

 29.5 



32.0 

 33.1 

 23.0 



°F. 

 114.0 

 120. 

 209.0 



137.7 



267.7 



2S0. 7 

 4S7. 5 

 337. 5 



138.8 

 187.2 



186. 6 

 199.1 

 26S.2 

 202.5 



549.4 

 588.0 



585. 6 

 628. 9 



690.0 



SUMMARY OF THE PRECEDING TABLE. 



Egg j 616 



Larva 313 



Pupa 530 



Total development, sum of stages 1, 459 



Observations on entire period 887 



Dans. 

 1.0 

 9.8 



19.3 

 19.6 



Average i Total 

 effective effective 

 tempera- ; tempera- 

 ture. I ture. 



32. 



631.2 

 632. 



