98 



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

 that the progen}^ 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 tliQse 

 observ^ations an ice box was especially designed and constructed to 

 facilitate observations at low and constant temperatures. (See 

 PI. XVI, fig. 70.) 



Table XXIII. — Thermal influence on development. 



Sta^e. 



^SS 



Larva 



Pupa 



Entire develop- 

 mental period. 



Number 

 of obser- 

 vations. 



385 



107 



36 



195 

 15 

 15 



161 

 81 



167 



29 



4 



96 



305 



66 



100 

 185 

 135 



Period. 



1902. 



Sept. 4 to Oct. 3 , 



Oct. 7 to Nov. 13 



Nov. 24 to Dec. 15 



Ice-box experiments, 1904 



Sept. 6 to Oct. 5 



Sept. 26 to Oct. 21 



Nov. 11 to Dec. 12 



Ice-box experiments, 1904 



Julv6 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. SO 



Sept. 16 to Oct. 15 



Oct. 8 to Nov. 16 



1903. 



June 4 to Julv 15 



Aug. 20 to Sept. 28. 



Ill ice box, 1904 



Average 



time for 



stage. 



Days. 



3- 



4-1- 



11.0 



5.1 



Effective tempera- 

 ture. 



Average. 



38.0 

 30.0 

 19.0 

 27.0 



7.5 



35.7 



267.7 



9.5 



30.6 



280. 7 



25.0 



19.5 . 



487. 5 



12.5 



27.0 



337.5 



3.5 



89.65 



138.8 



5.2 



36.0 



187. 2 



6.0 



31.1 



186.6 



7.6 



26.2 



199.1 



14.5 



18.5 



268.2 



7.5 



27.0 



202.5 



13.4 



41.0 



549.4 



17.5 



33.6 



588.0 



20.3 



29.5 



598.8 



18.3 



32.0 



585. 6 



19.0 



33.1 



628.9 



30.0 



23.0 



690.0 



Total. 



114.0 

 120.0 

 209.0 

 137.7 



SUMMARY OE THE PRECEDING TABLE. 



Stage. 



Total 

 observa- 

 tions. 



Average 

 period 



for 

 stage. 



Average 

 effective 

 tempera- 

 ture. 



Total 

 effective 

 tempera- 

 ture. 



Egg 



Larva 



Pupa 



Total development, sum of stages 

 Observations on entire period 



616 

 313 

 530 



Days. 

 4.0 

 9.8 

 5.5 



°F. 

 34. 

 32.2 

 33.2 



1,459 



887 



19.3 

 19.6 



32.9 

 32.2 



°F. 

 136.0 

 315.6 

 182.6 



634.2 

 632.0 



