CONTROL BY WINTER CLIMATIC CONDITIONS. 17 



middle of De vSoto, Sabine, and A^tiioii paiislics niid the \\<'stcin 

 third of Calcasieu and Cainei-on ])arishes, nearly ])arallol to the west- 

 ern boundary of the State. Tn other words, throiii^di the nnfaA'orable 

 climatic conditions following: \\\o disixM-sion of l!)()l the \\('e\il was 

 exterminated throiiixhoTit practically two-thii-ds of the area, in Lou- 

 isiana which had first become infested by the weevil dispersion of 

 that year. From tlu^ n^ports from Loiiisiana of the Weather l>iii('an 

 for 1904 and 1905 it appears that killing]: frosts occurred <i:enerallv 

 throiio;h the State abont November 13 to 15, 1904. The teniperatnre 

 and rainfall conditic^is within the infested area from that time till 

 the end of December were not far from normal, tho;i<i;h the rainfall 

 (hn-ini]: December was very heavy east of the infested area. Durint]; 

 damiary the temperature in the infested area averaged about 5 degrees 

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

 averaging 9 degi'ees 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 wee^^l has been obliged to withstand, as a usual occurrence, in 

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

 atures it probabh^ explains in large measure the extermination of 

 the weevils throagh 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 wdiich 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 Avithin the weevil-infested 

 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 opportimities 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 injur}^ 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 



