94 



In the laboratory uninfested squares were exposed to active weevils 

 for oviposition, and the supply of clean squares was renewed each day. 

 The beginning of the cycle was thus known to within a few hours. 

 The squares with eggs were carefully kept and the date of emergence 

 of each adult was then noted. To the period thus found must be 

 added the time intervening between the leaving of the square and the 

 deposition of the first eggs. This gives the period of the life cycle. 

 The material upon which these observations were made was necessarily 

 other than that used in determining the duration of the various stages. 

 The period in bolls is far different from that in squares. The figures 

 here given refer to squares. 



Table XXII. — Period of life cycle in squares. 



Observations. 



Time in period of 

 development. 



Average time. 



Temperature. 



Period covered. 



Num- 

 ber. 



Range. 



Average. 



Adult to 

 oviposi- 

 tion. 



Period of 

 cycle. 



Average Total 

 effective. 1 effective. 



1902. 



96 



305 



66 



100 

 180 



469 



Days. 



10-18 

 12-25 

 14-23 



12-22 

 13-26 



12-30 



Days. 



13.4 

 17.5 

 20.2 



18.3 

 19.0 



20.0 



Days. 



5.0 

 7.0 

 9.0 



5.6 

 5.0 



5.0 



Days. 



18.4 

 24.5 

 29.2 



23.9 

 24.0 



25.0 



°F. 



41.0 



33.64 



29.5 



32.0 

 33.1 



39.1 



°F. 

 754.4 



September 16 to October 15 



823. 2 

 864. 4 



1903. 

 Field, first generation- 



764.8 



August 20 to September 28 



1904. 

 Field , generations 1-5 



704. 4 

 975.0 



Total 



1, 216 



10-30 



18.5 



5.8 



24. 34 35. 88 



873.3 











These observations cover the season from June 1 to November 16. 

 Eeproduction undoubtedly begins somewhat earlier and continues 

 later in the average season at Victoria, but any differences which 

 might be found at the extremes would not material!}^ affect the loca- 

 tion of the mean in so large a series. The influence of varying tem- 

 perature during the same period but in different seasons is clearly seen 

 by a comparison of the figures for August 10 to September 30, 1902, 

 with those for August 20 to September 28, 1903. The period for 

 1902 was exceptionally warm, as shown by the high average effective 

 temperature, while in 1903 it was decidedly cooler, the difference 

 averaging 8° F. ; consequently the average period for the cycle was 

 fully six days greater in 1903 than in 1902 at the same season. 



Determinations of the duration of the life cycle in bolls have been 

 made in only a few instances. In 7 cases between August 15 and 

 November 11, 1903, the average time required from the deposition of 

 the egg to the escape of the adult from the opening boll was 61 days. 

 The average effective temperature for the period was 31.7° F., and 



