58 HIBERNATION OF THE COTTON BOLL WEEVIL. 



While it is probable that a study of maximum and minimum tem- 

 peratures is really more accurate, from a scientific point of view, 

 the mean average temperature, representing one-half of the sum of 

 the maximum and minimum for each day will be sufficiently exact 

 and a more simple manner of expressing the relationship existing 

 between temperature and weevil activity. The significance of the 

 term "effective temperature" has previously been explained (p. 24). 

 Upon the temperature charts the line representing 43 degrees is 

 therefore exceptionally emphasized. Wherever the temperature line 

 is above this point it represents effective temperature. Whenever 

 it falls below the 43-degree line it is possible that frosts may occur 

 if other atmospheric conditions are coincident!}' favorable. 



Whenever the minimum is noted to be 32 degrees or below, the 

 actual temperature occurring is given in its appropriate place upon 

 the record. When the temperature rises above 80 degrees, establish- 

 ing a new maximum, the occurrence is also shown by the actual 

 record given upon the charts. 



Since it is impossible for weevil emergence to occur at any temper- 

 ature below 43 degrees, that point is considered as initial in the lines 

 giving the records of the activity of weevils. The actual number of 

 weevils found active at various dates is shown at the top of the line 

 in each case. 



ENTRANCE INTO HIBERNATION. 



In each locality there occurred a considerable decrease in tempera- 

 ture during the month of October, the minimum being reached about 

 the 31st. Tins, however, was not sufficiently cold to cause weevils to 

 hibernate in considerable numbers. During the following two weeks 

 the temperature ranged as high as the average for October. After 

 November 15, however, there occurred a very marked fall of tem- 

 perature, the minimum even as far south as Victoria establishing 

 itself at about 25 to 27 degrees. All cotton was killed by this freeze. 

 The count of weevils found active early in November indicated 

 merely that few weevils had entered hibernation at that time. Fur- 

 ther counts, made about November 30, showed that even so severe a 

 diop in temperature as had occurred did not immediately drive 

 weevils into hibernation. During the succeeding two or three weeks 

 the temperature again ranged fully as high as during October, and 

 apparently many weevils which had sought shelter after the freeze of 

 the night of November 19 again became active. This was indicated 

 by the large number of weevils found active at Calvert and Victoria 

 about December 10. About the middle of December another period 

 of low temperature occurred, which was followed by decreased activity 

 among the weevils, many of which did not, even then, seek shelter. 

 During the first three weeks of January the exceptionally warm 

 weather experienced throughout Texas drew a considerable number 



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