76 



and the adults of the first generation. As has been shown, the aver- 

 age period of oviposition among hibernated females is in some cases 

 fully 3 months, while it averages 48 days. The length of the full 

 life cycle for the first generation, as shown in Table XIX, is 24 days, 

 and as the time for the second generation would be slightly less, it is 

 evident that the first eggs for the third generation will be deposited 

 at the same time as those for the middle of the second generation, 

 and also with the very last of the eggs deposited by hibernated 

 females for the first generation. The great overlapping of genera- 

 tions thus produced prohibits the application of any of the common 

 methods of ascertaining their limits. The complexity indicated for 

 the first three generations becomes still further increased as the season 

 advances, so that in October, for example, a weevil taken in the field 

 might possibly belong to any one of six generations. Length of life 

 and the period of reproductive activity are important factors in deter- 

 mining the average number of generations. Periods of greatest 

 abundance can not be regarded as giving any reliable information 

 upon this point, since the number of weevils developed soon comes to 

 depend largely upon the supply of squares. 



In the case of the boll weevil, therefore, the information upon the 

 number of generations must be drawn from laboratory sources. Many 

 of the hibernated weevils continue to deposit eggs until the middle of 

 July, and some are active for fully a month longer. In 1903 the last 

 eggs from hibernated weevils were deposited on August 27. In the 

 course of breeding experiments made in 1902 it was found that many 

 weevils which had become adult about the 1st of August would con- 

 tinue to deposit eggs until the latter part of November. Considering 

 the longest-lived weevils and their last-laid eggs, therefore, it is easily 

 possible for two generations to span the entire year. The weevils 

 developing after the middle of November may go into hibernation, 

 and from their last-deposited eggs produce weevils whose last off- 

 spring will be ready for successful hibernation again. This conclu- 

 sion is based upon actual demonstration. 



The maximum number of generations will be found by taking the 

 first, instead of the last, deposited eggs in each case. Rather than lay 

 the conclusions open to question by taking the figures found for occa- 

 sional minimum length of the life cycle, we will take the 24-day 

 period, which has been shown to be the average between June 4 and 

 November 16. Without doubt hibernated females begin their repro- 

 ductive activity in average seasons by May 1, and their descendants 

 continue to develop normally until after November 15. Taking the 

 dates mentioned, however, as the average season for the weevils, we 

 find that eight generations, each having the average period of devel- 

 opment, may usually be produced within the year. 



In determining the average number of generations one-third the 

 average period of oviposition should be added to the average life cycle 



