38 



and dependent upon so many factors that it is difficult to nialve any 

 i2:eneralizations regarding it, but from tlie many observations made 

 Ave have drawn the following conclusions: Under the conditions for 

 the last two years at College Station the critical period in the relation 

 between the natural increase of squares and the increase of injury by 

 the weevil is during the lirst six to eight weeks after squaring com- 

 mences, which usually coincides more or less closely with the time 

 between the second and third broods of weevils. Therefore, if we 

 consider six weeks as the average time for cotton to square after 

 planting, the bulk of the bolls must be set between eighty-five and 

 ninety days after the time of planting. In other words, to escape 

 injury by the w^eevil cotton must be grown so that the first bolls will 

 commence to open about one hundred days after planting, and that all 

 the fruit which will probably be secured must be set forty-five daj^s 

 after the squares form. The advantages of early varieties, other 

 things being equal, is therefore apparent. 



But should the weevil increase more rapidly than observed we 

 Avould have injury even though the cotton were early. The rate of 

 increase of the weevil is therefore most important. From the studies 

 of Hunter and Ilinds we learn that a female normally lays about 150 

 eggs in about fifty-four days (average figui'es), and that nearly half 

 are deposited during the first third of the })eriod. Allowing twenty- 

 four days for development, they estimate the total normal period for 

 a generation to be forty-two days. By counts of iliousands of squares 

 at different seasons we have determined the average rate of mortality 

 of weevils in squares to be about 05 per cent. The sexes are prac- 

 tically equal in numbers. With these facts it is easy to compute that 

 if there be 2 weevils per 100 stalks on June 1 — about the number at 

 College Station — on the appearance of the second brood in mid-July 

 there would be 50 weevils, and these would prochice by September 1 

 1,250 adults. In other words, the second brood would l)e twenty-five 

 times and the third six hundred and twenty-five times the number of 

 the first. But although we have three broods in the field during this 

 time the increase is by no means so great. Were it so no cotton could 

 be raised. The increase of the second brood over the hibernated 

 brood is considerably less than twenty-five times, usually not over 

 fifteen times, and the total increase from June 1 to September 1 is 

 only about fifty times — certainly not over sixty-five times — instead 

 of six hundred and tw^enty-five times, as it should be theoretically. 

 The reason for this discrepancy is unknown to the Avriter, l)ut for it 

 the planter may be exceedingly thankful. It may be that (1) the 

 mortality of the immature stages is greater than determined, which 

 we decidedly doubt; (2) many of the adult weevils die or are de- 

 stroyed before reinx)ducing; or (3) the number of eggs laid and the 

 length of period of oviposition actually occurring in the field are 



