MORTALITY IN BOLLS VERSUS SQUARES. 35 



viving beyond six or seven days from the deposition of the eggs. Jf 

 to this percentage we add the 12 per cent which were found dvml 

 from some cause other than the three under consideration, but prin- 

 cipally due to proliferation, we have a total mortality of from 75 to 

 80 per cent. 



The average length of the developmental period from June to 

 October is shown in Bulletin 51, Bureau of Entomology, page 94, to be 

 between eighteen and twenty days. The mortality shown by these 

 records Occurs, therefore, during the last two-thirds of the period 

 between the deposition of the egg and the emergence of the adult 

 weevil. When it is considered that a considerable proportion of eggs 

 and very young larvae must also be destroyed, it becomes increasingly 

 apparent that but a very small percentage of the total number of 

 eggs deposited by the weevils in a field of cotton produce adults. 



It may seem that this tremendous destruction of weevil stages 

 would be sufficient to bring the weevils under practical control so 

 that the comparatively small remainder would produce little injury 

 to the crop. Such, however, is not the case. The fact is that in 

 nearly if not quite all of the fields examined the weevils were so 

 abundant as to destroy a large portion of the crop, and in most cases 

 it is probably true that the multiplication of the weevils was finally 

 limited by the amount of food supply present rather than by the 

 destruction of the weevil stages by all these factors of natural control. 

 This does not mean that the crop did not benefit by the destruction 

 of weevil stages accomplished, for had it not been for this checking 

 of the possible multiplication of the weevils few of the fields could 

 have produced a crop that would have been worth, the picking. 



Were it not for the fact that in nearly all cases the destruction of 

 the weevil stage occurs only after the weevil has destroyed the cotton 

 form, the crop might be much more largely benefited by this natural 

 control. Without the natural control existing, cotton production 

 within the weevil-infested area would be impossible; with it alone, the 

 continuance of cotton culture may still be possible; but only by sup- 

 plementing the work of nature by the most practicable methods known 

 can the balance be thrown largely in favor of the planter in producing 

 a very profitable crop. 



NATURAL CONTROL IN VARIOUS LOCALITIES. 



In the sections of Table III the data are divided according to the 

 class of forms examined in order to make apparent the varying dif- 

 ferences in tjie effects of the several factors of natural control upon 

 the weevil stages. in each class of forms. In studying the combined 

 effect, which is really the measure of control in any locality and for 

 any period of time, this separation into classes is no longer necessary. 

 For this reason the figures given in Table VI represent a combination 



