NATURAL CONTROL. 



129 



FATAL VARIATIONS OF TEMPERATURE. 



It has long been known that one of the most potent forces in insect 

 control is abnormal variation of temperature. Probably no stronger 

 illustration of such control could be produced than that afforded by 

 the conditions of the winter of 1910-11. 



Fig. 27. — Map showing dates of first killing frost in the area infested by the boll weevil, in the winter 



of 1909-10. (Original.) 



Fig. 28.— Map snowing normal dates of first killing frost in the southern United 8ta1 . I Vfter 

 Weather Bureau Bulletin V.) 



On October 29 to 30, 1910, a freeze occurred throughout the cotton 

 belt affecting all but a narrow strip of territory along the Gulf coast 

 and two small interior areas of Texas, as illustrated by the accom- 

 panying map (fig. 27). Another map (fig. 28) is presented to show 

 28873°— S. Doc. 305, 62-2 9 



