BIOLOGY OF THE MEXICAN COTTON BOLL WEEVIL. 



33 



hatching out the number that live to enter hibernation is greatly 

 decreased. The cessation of squaring naturally forces a considerable 

 number of weevils to attack bolls which otherwise might escape. 

 Whether the loss resulting from this attack is offset by an advantage 

 to the crop of the next season on account of the presence of fewer 

 hibernated weevils has not been fully determined. 



THE MAXIMUM NUMBER OF GENERATIONS OF THE BOLL WEEVIL UNDER 

 FIELD CONDITIONS. 



The number of generations of the boll weevil under field conditions 

 varies with the different seasons and on the different types of soil. 

 A very dry and hot season may affect either generation to such an 

 extent that the eggs deposited during the first half of the generation 

 may not produce weevils at all, and consequently the generation is 

 much prolonged. The following table shows the maximum number 

 of generations at Madison, Fla., under field conditions : 



Table XVI.— Maximum number of generations of the boll weevil bred in cotton 



squares, Madison, Fla. 



Generation. 



Date. 



Period 

 from 

 matur- 

 ity to 

 matur- 

 ity. 



Generation. 



Date. 



Period 

 from 

 matur- 

 ity to 

 matur- 

 ity. 



First generation: ■ 



June 1 

 June 22 



June 30 

 July 20 



July 28 

 Aug. 17 



Days. 



Fourth generation: 



Aug. 24 

 Sept. 16 



Sept. 23 

 Oct. 16 



Oct. 24 

 Nov. 17 



Days. 









30 



Second generation : 





Fifth generation: 







29 





32 



Third generation : 



Sixth generation: 







29 





33 









The average date of killing frost at Madison, Fla., according to the 10-year average of the United States 

 Weather Bureau, is November 29, therefore only six generations of weevils could develop under field con- 

 ditions. 



HIBERNATION OF THE BOLL WEEVIL IN FLORIDA. 



During the winter of 1918-19 three series of hibernation experi- 

 ments were conducted to determine the percentage of weevils sur- 

 viving the winter at Madison, Fla. The experiments were arranged 

 to secure data on the number of weevils surviving the winter in the 

 open fields and along ditch banks, in the woods oh the ground among 

 the leaves and other rubbish, and in the moss covered trees in the 

 woods (figs. 13, 14, 15). 



Large wire screen cages 3 by 3 feet by 4 feet high were used for 

 the hibernation experiments. The cages in the fields and on the 

 ground in the woods were filled with an equal amount of moss, leaves, 

 and cornstalks to represent approximately the material the weevils 

 would hibernate in under normal conditions. The cages installed 



