October, '11] cushman: biology of boll weevil 441 



' For determining the duration of the several stages of the develop- 

 mental period beyond the egg, a start was made with 107 eggs of known 

 date. The date of hatching was estimated on the basis of the incuba- 

 tion period as previously determined. Of the eggs used nine were 

 deposited June 27-28, five June 29-30, thirteen June 30-July 1, 

 forty July 1-2, twelve July 3-4, and twenty-eight July 6-7. The 

 incubation period for the last of these lots was placed at two and one 

 half days and for the others at three days. The squares containing 

 these eggs were opened a short time before pupation was expected to 

 take place. Thereafter they were examined daily and the dates of 

 pupation, formation of the teneral adult, and emergence recorded. 

 By these means the actual progress of the weevils from the egg to 

 emergence was ascertained with considerable accuracy. Of the orig- 

 inal 107 individuals, the larval period of 98, the pupal period of 50, 

 and the postpupal or teneral adult and total periods of 58 w^ere deter- 

 mined. 



The results obtained indicate that the larval period occupies slightly 

 less than one half of the total developmental period, and approxi- 

 mately equals the incubation and pupal periods combined. The 

 larval period showed somewhat greater variation than the inac- 

 tive periods, the excess being probably due to the drying of the opened 

 squares, while the egg and pupal periods were influenced largely by 

 the temperature. The variation of one to three days in the postpupal 

 period can be explained only by the peculiarities of the individual 

 weevils. 



The average mean total developmental period of the weevils under 

 observation was somewhat higher than of weevils from undisturbed 

 squares infested during the same period, due to the more rapid drying 

 of the opened squares. The average developmental period of the 92 

 weevils bred from unopened squares was 13.4 days, 0.4 of a day less 

 than for those in the opened squares. The average mean develop- 

 mental period as determined above taken together with the average 

 preoviposition period, shown in Table IV, gives an average total life 

 cycle, exclusive of the oviposition period of about twenty days. The 

 minimum, however, as shown by the figures of these two sets of obser- 

 vations, may be as low as sixteen days. 



The data on the total developmental period and its several divisions 

 are shown in Table VI. 



The developmental period for individual weevils throughout the 

 season was taken as the time between the average date of oviposition 

 and the average date of emergence. Since examinations were made 

 only once in twenty-four hours, this gives a possible variation of two 

 days, and, when one observation was omitted, of three days. Obtained 



