70 



THE MEXICAN COTTON-BOLL WEEVIL. 



Table XXVII. — Table to illustrate the effect of the time of falling upon the period of 

 development of -the boll weevil in squares. 



The average for the 664 stages covered in the table is 18.4 days, 

 which may be taken as the general average period of development in 

 squares. Figure 1 1 graphically illustrates Table XXVII. 



fO /S 2Q ZS 3 Q 



VARIATIONS DUE TO TEMPERATURE. 



It will be noticed that the average 

 period of development in squares 

 which have hung on the plant for 

 the same length of time varies with 

 the season, but an increase of tem- 

 perature regularly lowers the aver- 

 age developmental period. The 

 following diagram (fig. 12) has been 

 constructed from the average curves 

 determined for each of the stages 

 in the development and shows that 

 the range is from 13 davs at 88° F. 

 to 51 days at 62° F. 



By using the quantities deter- 

 mined by the curves in figure 12 it 

 is possible to chart the mean or nor- 

 mal developmental period by months for any given place with 

 known mean temperatures. This has been done on the following 

 diagram (tig. 13) for Victoria, Tex., Ardmore, Okla., and Vicks- 



Fig. 11.— Diagram illustrating effect of time of 

 falling of infested squares upon period of de- 

 velopment of boll weevil at Victoria, Tex., 

 August, 1904. (Original.) 



