SOMK FACTORS IN THE NATCPvAL OOXTItOL ( 

 MEXICAN COTTON BOLL WI:E\ IL. 



INTRODUCTION. 



Tho natural control of {ho cotton boll weevil is so broad a subject, 

 com]>risini2: the oil'ects of so many factors, some of wliicb aic iinper- 

 fectly known and understood, that anythinij: like a comprehensive 

 treatment of the subject is at present impossible. Doubtless numy 

 factors of some importance have not yet been studied. Of ibe fact 

 that some factors do accomplish the destruction ()l)serve(l in indi- 

 %T[dual cases we have no doubt. From extensive series of such obser- 

 vations we may be able to reason safely as to the general tendency 

 (^f those factors, and w^e may possibly be a])le to assign to them a 

 relative value in their tendency to control under the conditions then 

 prevailing, but we must recognize the fact that all these factors, 

 however many there may be, are so interrelated and their influences 

 imder varying conditions ma}^ so essentially differ that a study of 

 them becomes an exceedingly difTicidt })r()blem. 



CONDITIONS REQUIRING CONSIDERATION. 



The magnitude of the w^ork involved is directly increased by the 

 extent of the area affected and by the variations in climatic, geo- 

 logical, and cultural conditions wdiich are encountered within the 

 weevil-infested area. While some factors may be studi<Ml throiigli 

 multiplied observations as to their effect in individual cases, others 

 must be considered from the broader standpoints of the general 

 movement of the species, crop production, etc. 



Temperature and moisture conditions are undoubtedly the ])rinci- 

 pal climatic factors which govern in a general way the distribution 

 of every species. Of these two factors, temj)erature is un(|iies- 

 tionably the more important. The effect of this factor uj)oii the 

 continued spread of the boll weevil has been a subject of interest 

 to entomoloofists ever since the weevil became a fad oi- in the cidhNa- 

 tion of cotton in Texas. It has been supposed that the wccniI, 

 coming originally from a habitat nmch farther south, would linally 



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