24 



INSECT EN-EMIES OF THE BOLL WEE^T:L. 



Highest records of total insect control of the holl weevil — Continued. 



IN HANGING SQUARES. 



Locality. 



Date. 



Number 

 of stages. 



Percent- 

 age of 

 insect 



control. 



Athens, Tex 



\ua;. 1, 1907 



75 

 55 

 57 

 87 

 99 

 2U 

 253 



84 00 



Arlincrton, Tp\- 



July 1909 



75 11 



DaUas, Tex 



..do 



69.99 



Victoria, Tex 



Julv29, 190S 



58.54 



Waco, Tex 



July 1,1906 



56.56 



Mansfiplfi, T/a ... 



Sept. 1, 1906 . 



50 90 



Victoria, Tex 



Aug. 1, 1907 



50.00 









IN HANGING BOLLS. 



Mansfield, La. 

 Waco, Tex... 

 Overton, Tex. 

 Mansfield, La. 



Sept. 29, 1906. 

 Aug. 1,1906.. 



do 



Sept. 24, 1906. 



58.30 

 42.04 

 40. 50 

 33.00 



THE CORRECT BASIS FOR COMPARISON OF MORTALITY STATISTICS. 



As has been explained, the examinations have been made from 

 various sources. It is therefore necessary to arrive at some true 

 basis for the comparison of these data before an exact knowledge of 

 the conditions existing can be obtained. The first mortality of the 

 weevil is that due to prohferation. Dr. Hinds, in Bulletin 59 of 

 this bureau, has shown that the average mortality of weevil stages 

 in squares from prohferation is 13.5 per cent and that the average 

 mortahty in bolls is 6.3 per cent. In the absence of further data 

 these two percentages are used as a basis for obtaining the weighted 

 average mortality. 



As nearly as the proportion can be estimated throughout the entire 

 season, 15 per cent of the weevil stages are to be found in boUs and 5 

 per cent in hanging forms. Whether these arbitrary estimates be 

 true or not, this is the only manner in which it will be possible to 

 compare the mortality by the different factors in the various years. 

 On this basis, therefore, a series of hypothetical tables has been 

 erected. 



In order to show how the hypothetical average differs from the 

 average obtained from the total examinations, two tables are given 

 for each year, the first being a table giving the actual conditions in 

 the four classes of infested material and the second table being a 

 hypothetical table based upon 10,000 weevil stages on the arbitrary 

 basis of 5 per cent of the stages in hanging forms and 15 per cent of 

 the stages in boUs. The process continues by first subtracting the 

 mortality by prohferation and then computing the mortality from 

 chmate, predators, and parasites from the remainder. The percent- 

 ages of mortality given in the total line are based upon the total of 

 10,000 stages. 



