72 



THE MEXICAN COTTON-BOLL WEEVIL. 



interesting to note that Ardmore shows only four and one-half months 

 in which the developmental period can be under 30 days. Adding 

 the preoviposition period to the developmental period, it is evident 

 that unless the weevil adapts itself to the northern conditions latitudes 

 north of Ardmore can have only a fraction over three generations in a 

 year, whereas Victoria, with seven months in which the develop- 

 mental period is less than 30 days, frequently has six generations. 



VARIATIONS OF DEVELOPMENT IN BOLLS. 



It is of interest to note the variation in development in bolls due to 

 the length of time the boll hangs on the plant. At Victoria, Tex., in 

 June the development was 15 days for a boll hanging 1 day and 39 

 days for a boll hanging 26 days, while in bolls which did not drop, it 

 frequently took over 60 days, with 67 as the maximum. The average 

 developmental period of 67 weevils at Victoria and Dallas was 41 days, 

 or more than twice the average period of weevils in squares. This 

 difference may be considered as due to a combination of the factors of 

 lower temperature, greater humidity, and less nutritious food. 



MISCELLANEOUS VARIATIONS. 



There are also some variations in development which can not be 

 attributed to any of the causes cited above. Undoubtedly the insect 

 adapts itself to the supply and condition of the food available. Con- 

 sequently, under the same climatic conditions weevils in very small or 

 delayed squares develop more quickly than those where the food is 

 more suitable. Such variations are illustrated by Table XXVIII, 

 which relates to the developmental periods of weevils of the third 

 generation at Alexandria, La., in 1907. 



Table XXVIII. — Table showing variations in the developmental period of boll urevils 

 in the third generation at Alexandria, La., in 1907. 



Date of oviposition. 



September 2. . 



Do 



Do 



Do 



Do 



September 1-4 

 September 1 . . 

 September 4. . 

 Septembers.. 

 September 3. . 

 September 4-5 

 September 1-5 

 September 2. . 



Do 



Do 



Do 



September 3-4 

 September 2-4 

 September 2. . 

 August 31 



Do 



Do 



September 1. . 



August 31 



September l. . 



August 31 



Do 



August 20 



Do 



Num- 

 ber of 

 stages. 



Total 

 egg 

 days. 



1 

 4 



4 

 7 

 ins 

 2 

 3 

 4 

 4 



20 



00 



5 



10 



4 



24 







36 



18 



42 



9 



9 



4 



12 



12 



6 



Aver- 

 age 

 egg 



period. 



Total 

 larva 

 days. 



24 



10 

 00 



210 

 20 



112 

 40 

 72 

 21 



144 

 81 



Aver- 

 age 

 larval 

 period. 



Total 

 pupa 

 days. 



Aver- 

 age 

 pupal 

 period. 



28 



12 

 50 

 120 

 45 

 90 

 10 

 72 

 15 

 72 

 27 



Total 

 weevil 

 days. 



12 

 39 

 26 

 26 

 130 

 390 

 70 

 224 

 56 

 108 

 42 

 258 

 120 



total 

 period. 



