30 NATURAL CONTROL OF THE COTTON BOLL WEEVIL. 



From a study of the totals in each section of this table it appears 

 that the highest average percentage of mortality from all three 

 causes considered was found among the fallen squares, where it 

 reached 60.5 per cent. The next highest average mortality occurred 

 in the hanging, dried squares, with 52.6 per cent. The mortality in 

 the two classes of bolls is very similar, with 33 and 30.4 per cent. 



The data include only examinations of cotton forms which had 

 been destroyed by some cause. In the majority of cases the de- 

 struction of the form could be attributed directly to weevil attack. 

 The data upon this point are stated in subsequent tables. (See 

 pp. 64-72.) 



A comparison of the mortality records in hanging versus fallen 

 forms (including both squares and bolls) shows that among the 

 9,663 stages found in hanging forms there was an average mortality 

 of 40 per cent, while among the 29,328 stages in fallen forms there 

 was an average mortality of 56 per cent. In hanging bolls the mor- 

 tality is 30.4 per cent; in fallen bolls, 33 per cent; in hanging 

 squares, 52.6 per cent; in fallen squares, 60 per cent. These figures 

 show a consistent difference in favor of the fallen forms. 



Parasites work more freely in the forms that remain attached to the 

 plants than in those which fall to the ground, but in neither class of 

 forms is their work as important as is that of the ants or even the effect 

 of heat or drying. From many observations as to the stage of the 

 parasite at the time of examination and from a general knowledge of 

 the time that must have passed between it and the parasite attack, it 

 appears that, as a rule, the parasite egg is deposited at about the time 

 the square or boll withers. If this be the case, it is probable that the 

 increased length of time during which the forms that remain attached 

 and dry upon the plant are exposed to the parasite attack may explain 

 the greater percentage of parasitization found in the hanging forms. 

 In hanging forms parasitization amounts to 9 per cent, while among 

 fallen forms it averages only 2.8 per cent. 



The average total mortality among all classes of forms caused by the 

 three factors was 52 per cent. As the weevil does not pass beyond the 

 influence of these factors of control until after it has become adult and 

 emerged from the square or boll, it is evident that among the 13,000 

 living stages found present there might still have occurred a very con- 

 siderable mortality before all could have become adult and emergence 

 taken place. The larval and pupal stages, which number over SO per 

 cent of all the living stages found present, are especially susceptible to 

 the influence of the three natural factors of control under considera- 

 tion. It would be very conservative to assume that fully one-half of 

 the living stages present would have been destroyed had the forms 

 been allowed to remain exposed to the influence of the factors of con- 

 trol until all surviving adults could have emerged. This would have 



