CONTROL BY WINTER CLIMATIC CONDITIONS. 17 



middle of.De Soto, Sabine, and Vernon parishes and the western 

 third of Calcasieu and Cameron parishes, nearly parallel to the west- 

 ern boundary of the State. In other words, through the unfavorable 

 climatic conditions following the dispersion of 1904 the weevil was 

 exterminated throughout practically two-thirds of the area in Lou- 

 isiana which had first become infested by the weevil dispersion of 

 that year. From, the reports from Louisiana of the Weather Bureau 

 for 1904 and 1905 it appears that killing frosts occurred generally 

 through the State about November 13 to 15, 1904. The temperature 

 and rainfall conditions within the infested area from that time till 

 the end of December were not far from normal, though the rainfall 

 during December was very heavy east of the infested area. During 

 January the temperature in the infested area averaged about 5 degrees 

 below the normal, while in February it reached an extreme departure, 

 averaging 9 degrees below normal. During these two months the 

 rainfall in this area was very heavy, averaging more than 10^ inches. 

 Though this appears to be not more than 1 or 2 inches in excess 

 of the normal rainfall during these two months, it is far more than 

 the weevil has been obliged to withstand, as a usual occurrence, in 

 Texas, and in conjunction with the very exceptionally low temper- 

 atures it probably explains in large measure the extermination of 

 the weevils through practically all of the territory entered by them 

 in the fall of 1904 after the latter part of August. It remains to be 

 seen whether the heavy winter rainfall which normally occurs in 

 this Louisiana territory will, as a usual thing, prove to be an impor- 

 tant factor in reducing the number of weevils hibernating successfully 

 within this area. 



A somewhat similar reduction of infested area occurred in northern 

 Texas coincident with that in Louisiana, but, owing to the demands 

 of other lines of investigation in Texas, it was impracticable to make 

 as thorough an investigation to determine the limit of infestation in 

 July, 1905, in Texas as was done in Louisiana. 



As the weevil seems to be acquiring a greater power of resistance 

 to low temperatures as it spreads farther northward, the value of 

 this factor for any locality now included within the weevil-infest ed 

 area would seem to be gradually decreasing. The efficiency of winter 

 cold is very largely affected by the coincident humidity and by the 

 abundance and favorable character of the opportunities for shelter 

 which may be obtained by the hibernating weevils. 



Besides the direct effect upon weevil survival, winter climatic 

 conditions exercise an indirect effect upon weevil injury during the 

 following season by their influence upon the survival of cotton roots. 

 This is an especially important consideration in southern Texas, where 

 during many seasons a considerable proportion of old roots survive-, 

 11575— Bui. 74—07 2 



