24 



HIBERNATION OF THE COTTON BOLL WEEVIL. 



This table serves to show in a graphic way the extent of the period 

 of entrance into hibernation, the varying duration of the period 

 for the same locaHty in different seasons, and the generally later 

 date of entrance in southern localities as compared with more northern 

 localities in the same season. It also shows the duration of the 

 period as compared with the mean average temperature prevailing. 

 In general it appears that the greater the drop in temperature the 

 shorter will be the period of entrance into hibernation. 



Table VI. — Periods of entrance into hibernation, and temperatures. 



Year. 



Locality. 



Period. 



Limits. 



Days. 



Temperature. 



Mean 

 average. 



Efiective.a 



1903.... 

 1903.... 

 1904.... 

 1904.... 

 1905.... 

 1905.... 

 1906.... 

 1906.... 



College Station, Tex. 



Victoria, Tex 



Corsicana, Tex 



Victoria, Tex 



Dallas, Tex 



Victoria, Tex 



Dallas, Tex 



Victoria, Tex 



Nov. 15-27 



Nov. 15-30 , 



Nov.lO-Dec. 5.. 

 Nov. U-Dec. 8. 

 Nov. 29-Dec. 8. 

 Nov. 30-Dec. 18, 

 Nov. 12-Dec. 8. . 

 Nov. 9-Dec. 21.. 



49.5 

 53.0 

 55.0 

 57.5 

 40.5 

 50.0 

 53.0 

 60.4 



6.5 

 10.0 

 12.0 

 14.5 

 None. 



7.0 

 10.0 

 17.4 



oln studj'ing the relationship of temperature conditions to weevil activity the term "effective tem- 

 perature" is used to designate the excess of temperature above 43 degrees F. It has Iseen estimated that 

 43 degrees marks approximately the beginning of activity with most animals, and experiments have shown 

 that this is equally tnie of the boll weevil. Below this temperature the weevils are usually inactive. 

 Above it they may move, feed, and reproduce with increasing rapidity as t-he temperature increases. From 

 this explanation it may be readily undeistood that the column sliowing the decrease of etfective tem- 

 perature is really the most significant in connection with the inactivity or hibernation of the weevil. 



It is undoubtedly true that minimum temperatures have a special 

 influence in checking the activity of the weevil in spite of the fact 

 that they may be below 43 degrees F. Wlien the temperatm-e falls 

 to 32 degrees or lower the food supply of the weevils is usually rather 

 completely destroyed, and this fact may serve to discourage subsequent 

 activity on the part of the weevils, even though the temperature 

 conditions miglit otherwise favor it. 



From this table it may be seen that the shortest period of entrance 

 into hibernation of which we have record is ten days. This occurred 

 at Dallas, when the mean average temperatvire was 9 degrees lower 

 than that for any other period which has been studied. 



In regard to the limits assigned to the period for Victoria in 1906 

 it may be stated that hibernation was probably only partial at that 

 place at any time during the winter of 1906-7. The limits of the 

 period that have been given are based on field notes made about the 

 middle of November indicating the beginning of the period, and 

 temperature records covering the coldest period that occurred during 

 December. The mean average temperature during November for Vic- 

 toria was 60.4 degrees, the range being from an absolute minimum of 

 27 degrees to an absolute maximum of 84 degrees. The temperature 



