75 



Tabi.r XIX. — Length of life cycle. 



These observations cover the season from June -t to November IG. 

 Reproduction undoubtedlj^ begins somewhat earlier and continues 

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

 might be found at the extremes would not materiall}^ 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 elearlj^ 

 seen by a comj)arison of the figures for August 10 to September 30, 

 1902, with those for August 20 to September 28, 1003. The period for 

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

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

 averaging 8° F. ; consequently the average length of the cycle was 

 fully six days greater in 1003 than in 1002 at the same period. 



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

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

 November 11, 1003, 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 

 the average total effective temperature required for development in 

 bolls was therefore 1,933.7° F., or nearly two and one-half t'imes as 

 much as in squares. Several larvte often develop within a single boll 

 (PI. XI, fig. 43). They appear to remain in the larval stage until the 

 boll becomes sufficiently mature or so severely injured as to begin to 

 dry and crack open. When this condition of the boll is reached, pupa- 

 tion takes place, and by the time the spreading of tlie carpels is suffi- 

 cient to permit the escape of the weevils they have become adult. 



BROODS OR GENERATIONS. 



The term "brood" can hardly be applied in its usual sense to the 

 generations of the weevil, as was pointed out by Doctor Howard in 

 the first circulars of the Division dealing with the problem. For sev- 

 eral- reasons no line of distinction can be drawn between the genera- 

 tions at any season of the year, not even between hibernated weevils 



