SEASONAL HISTORY. 69 



LIFE CYCLE. 

 DURATION OF LIFE CYCLE. 



We have shown that the average duration of the egg stage under 

 different conditions is 3.7 days, of the larva 8.5 days, of the pupa 

 15.1 days, of the preoviposition period 7.7 days, and of the oviposition 

 period 31 days. Consequently, the average time from the deposition 

 of the egg to the completion of oviposition by the resulting adult is 

 56 days. The average required for the combined egg, larval, and 

 I pupal stages is 17.3 days. The larva requires about 2\ times as 

 many days as the egg, and the pupa about two-thirds of the time 

 required for the development of the larva. 



SEXUAL VARIATIONS. 



There are several factors which govern the duration of the life 

 cycle of the weevil. The factor which is of least importance, if, 

 indeed, it is of any importance, is that of sex. Mr. R. A. Cushman, 

 in experiments at Tallulah, La., in 1910, in which squares were under 

 more or less uniform climatic conditions, found that 475 males 

 averaged in development 13.88 days, while 393 females averaged 

 13.49 days. The figures are so nearly equal that there is great doubt 

 as to whether the sexes require different periods. 



VARIATIONS DUE TO LOCATION OF DEVELOPING STAGE. 



As has been stated, the tendency of the squares to hang or fall 

 is a determining factor in the length of the developmental stage. In 

 a humid region, however, the difference may be very small. At 

 Alexandria, La., in 1907, it was found that the average developmental 

 period during the first 19 days of August in fallen squares was 15.3 

 days and in hanging squares was 15.1 days. 



VARIATIONS DUE TO TIME OF FALLING OF INFESTED SQUARES. 



The period preceding the falling of the squares to the ground seems 

 to be one of the strongest factors in determining the length of the 

 developmental stages. To illustrate this, at Victoria, Tex., in August, 

 1904, it was found that the average development in squares which 

 hung only 1 day was 13 days, whereas for squares which hung 18 

 days, the development was 28J days; also at Dallas, Tex., in August, 

 1906, the average development in squares which hung 6 days was 

 19 days and in squares which hung 22 days was 36 days. We pre- 

 sent Table XXVII, which shows in general that the difference in 

 the time required for development in hanging and in fallen squares is 

 proportionately the same in all months of the year and at all places 

 where observations have been made. 



