INFLUENCE OF DRY SEASON ON SUCCEEDING SEASON. 15 



In connection with this table it should be noted that the tempera- 

 ture conditions during the six months which are of greatest signifi- 

 cance varied but little from the normal. In rainfall, however, a 

 great deficiency occurred both in 1901 and in 1902. Undoubtedly 

 the continuance of the drought throughout the season was more 

 influential than was the boll weevil in reducing the crop for the years 

 1901 and 1902, which were almost complete failures. Through the 

 season of 1903 there fell a large excess of rain and it was well distrib- 

 uted. This would produce conditions very favorable for weevil 

 multiplication and injury, but in spite of this the cotton crop for 1903 

 for this county was nearly ten times as large as during the preceding 

 year. In 1904 both temperature and rainfall were nearly normal, 

 but the effect of the large number of weevils passing through hiber- 

 nation from the season of 1903 is very conspicuously shown by the 

 reduced size of the crop of 1904. This is an illustration of the control 

 of the boll weevil by the unfavorable climatic conditions of an entire 

 season so effective that the weevil failed to become greatly injurious 

 to the succeeding crop in a season when the climatic conditions were 

 unusually favorable for its increase. 



CONTROL BY WINTER CLIMATIC CONDITIONS. 



Exceptionally low winter temperatures have occasionally proved 

 sufficiently effective to exterminate the weevils from certain areas 

 which had become recently infested and within which the weevils 

 had not had time to become firmly established. This has been 

 illustrated by several well established cases in northern Texas and 

 Louisiana during the past few years. 



Weevils were first found near Sherman, Tex., in the fall of 1903, 

 when the northern limit of the dispersion reached to within a few 

 miles of that place. No weevils could be found in that region in 1904 

 or until the dispersion of 1905 had taken place, thus proving that the 

 few weevils reaching there in 1903 had failed to reproduce or that 

 they and their progeny were completely exterminated by the winter 

 conditions of 1903-4. Weather Bureau records show that the 

 minimum temperature in this locality during the winter of 1903-1904 

 was 12° F. on January 26, 1904, and that the average monthly tem- 

 peratures for January, February, and March at Sherman were + 2.6°, 

 + 10°, and +6.9° above normal, respectively. It hardly seems prob- 

 able, therefore, that the weevils failed to maintain themselves in 

 this case solely on account of low winter temperatures. 



