98 



THE MEXICAN COTTON-BOLL WEEVIL. 



fortunate individuals to resume its activity upon warm days. If 

 at first the shelter which weevils find is only slight they will be easily 

 influenced by succeeding warmth, and in another period of activity 

 will be likely to find better protection. Their flight upon warm days 

 undoubtedly leaves large numbers of them outside of the cotton 

 fields, where they are more likely to find favorable shelter than within 

 the fields themselves. 



From this explanation it will be understood that it is rarely pos- 

 sible to indicate by a single date the time when weevils enter hiber- 

 nation. It may be better expressed as a period within the limits of 

 which a large majority, though possibly not all, weevils may seek 

 shelter. Naturally this time varies according to the seasonal tem- 

 perature conditions, so that in a certain locality it may occur several 

 weeks earlier in one season than in another. It is also evident that 

 differences in temperature conditions due to latitude or altitude will 

 cause a similar variation in the time when weevils enter hibernation. 1 



In Table XXXIII are shown the times of the year in which the weevils 

 entered hibernation in the experiments of 1903 to 1906, together with 

 the temperature conditions prevailing. The table shows the relation- 

 ships between humidity and temperature and the length of the period 

 of entrance into hibernation. In short, it may be stated that the 

 lower the mean temperature the shorter the period of entrance. 

 Sufficient information is not at hand to show positively the influence 

 of humidity, but it is evident that there is a decided influence. 



Weevils can not be forced to hibernate when conditions do not nor- 

 mally induce hibernation. If kept without food, they will starve. 

 The real bearing of this statement will be brought out later in con- 

 nection with the summaries of the survival in its relation to the 

 time of beginning hibernation. (See Table XL VI.) 



NUMBER OF ADULT WEEVILS ENTERING HIBERNATION. 



Of course the number of adult weevils entering hibernation is a 

 variable quantity, owing to the differences in the percentage of infes- 

 tation in various regions and seasons. Examinations m heavily 

 infested regions have shown averages as high as 58,000 adult weevils 



1 This and the preceding paragraph are remodeled from Bull. No. 77, Bureau of Entomology. 



