RETENTION OR SHEDDTNG OF INFESTED FORMS. 33 



ants caused a mortality of 4.6 per cent among hanging forms and 22.4 

 per cent among fallen forms, while parasites caused a mortality of 

 2.2 per cent among hanging forms and only 2.1 per cent among fallen 

 forms. 



The conclusions may also be drawn from a study of the proportion 

 of weevil stages found dead in each class of forms, in connection with 

 the factors causing death and the proportion of forms to weevil 

 stages in each class examined. In this way it appears that the low- 

 est total mortality was found in the hanging bolls which dried upon 

 the plant, being in this case 30.4 per cent. For fallen bolls this per- 

 centage was 33.4, in hanging squares there was a mortality of 52.6, 

 while in fallen squares it amounted to 60.8 per cent. Taking next a 

 comparison of hanging and fallen forms, it appears that there was an 

 advantage during the season of 1906 of 16.2 per cent greater total 

 mortality among the fallen forms. 



As to the factors which were most effective in producing this mor- 

 tality, it appears that among hanging forms ants produced 46.5 per 

 cent of the total mortality found, while in fallen forms they were 

 responsible for 53.2 per cent of the total mortality. It is evident, 

 $] j $e ? that in either hanging or fallen forms Solenopsis geminata 

 v\as tL M most important summer factor in 1906 in controlling the 

 weevil. When it is considered that a large majority of the infested 

 forms fall, it becomes still more certain that the effectiveness of the 

 factors naturally tending to control weevil multiplication is greater 

 when the infested forms are shed than when they are retained by the 

 plant. 



From these data it appears that it is more desirable that plants 

 shed their infested forms completely and quickly after the infesta- 

 tion takes place than that they should retain them, allowing the 

 weevil stages therein to develop under the smaller influence of natural 

 control to which they would then be subjected. 



MORTALITY IN BOLLS VERSUS SQUARES. 



It should be stated that in these examinations no attempt was 

 made to determine the mortality among weevil stages in large bolls 

 which continued their development in rnte of the weevil attack. 

 In such bolls it is obvious that heat or drying can have had little if 

 any effect upon the weevil stages. Ants do not enter green, growing 

 bolls, though they frequently destroy weevil stages which become 

 more easily exposed to their attack through the opening of the bolls. 

 Instances have been found of parasitism of weevil stages in large 

 bolls. Proliferation is, however, an active factor which has been 

 found in the examination of more than 12,000 locks to produce an 

 increase m mortality of weevil stages amounting to between 6 and 7 

 per cent. 



11575— BuL 74—07 3 



