108 



THE MEXICAN COTTON-BOLL WEEVIL. 



Figure 23 shows graphically that climate influences the time of 

 beginning emergence. It also has a decided effect upon the sub- 

 sequent emergence. In Table XLII is shown what effect the daily 

 mean temperature has upon the hibernating weevil. 



Table XLII. 



■The relation of emergence of the boll weevil to increase in temperature at 

 Keatchie, La., and Dallas, Tex., 1906. ' 



1 Modified from Bull. 77, Bureau of Entomology, p. 44. 



The number of weevils emerging under 57° F. is very small indeed. 

 From that point the emergence increases with the increase in tem- 

 perature until a majority of the weevils have emerged. Most 

 weevils have been found to leave their winter quarters during a 

 temperature averaging between 64° and 78° F. At Keatchie 75 



Eer cent and at Dallas 96 per cent of the total emergence took place 

 etween these limits. At Dallas the largest emergence occurred 

 between temperatures of 64° and 68° F., while at Keatchie the 

 largest emergence occurred between 74° and 78° F. In a preced- 

 ing paragraph we have shown that higher temperatures are neces- 

 sary to affect the weevils hibernating in Louisiana, apparently 

 because of the heavier shelter. 



RATE OF EMERGENCE. 



With a long-continued emergence period it is important to deter- 

 mine whether the rate of emergence is equal at all times or has its 

 periods of retardation and acceleration. Upon charting the per- 

 centage of total emergence for each week it was noted that the 

 Texas and Louisiana points differed considerably. On the accom- 

 panying diagram (fig. 24) the four Texas series are consolidated to 

 give the average rate, and likewise the four Louisiana series are 

 consolidated, while in Table XLIII the records for each locality are 

 given. It is immediately apparent that the emergence begins much 



