PREFACE. 



In the earlier work of the cotton boll weevil investigation particular 

 attention was given to the life history and habits of the boll weevil and 

 the direct effect of these upon cotton production. 



These phases of the investigation have been described in a number 

 of circulars and bulletins of the Bureau of Entomology, among which 

 the reader is referred especially to Bulletins 45 and 51, by Hunter and 

 Hinds, and Bulletin 63, Part I, by Prof. E. D. Sanderson. The pres- 

 ent bulletin deals especially with three factors of natural control in 

 regard to which our knowledge has been largely extended by the work 

 done during the season of 1906. 



Those who are engaged in the cotton boll weevil investigations of 

 the Bureau of Entomology are frequently asked if the boll weevil is not 

 a passing pest, which may be expected in time to leave the cotton 

 fields where it now occurs, because of a continuation of the onward 

 movement by which it has spread through the great area which it now 

 infests. This idea is doubtless based upon the fact that in any locality, 

 in a series of seasons, there is likely to occur one season in which there 

 will be a marked decrease in the abundance of the weevils. As a con- 

 sequence of this an unusually good crop may be made, and after such a 

 season with little weevil injury the planter is naturally inclined to 

 anticipate that the weevil may never again become as serious a pest as 

 it has been in the past. 



The continuation of this investigation through a number of years 

 has made it possible to determine that local variation, such as has been 

 referred to, may be due directly to the influence of certain natural fac- 

 tors which, either singly or in combination, have exercised an unusually 

 large degree of control upon the weevil. It has been possible to deter- 

 mine the most important factors concerned in this control and in some 

 measure to show their relative importance. Extensive observations, 

 however, have but confirmed the impression, which was formed years 

 ago by entomologists engaged in studying this question, that the 

 boll weevil is not a passing pest, but rather an enemy which must be 

 taken into account every year by the grower of cotton throughout the 

 infested area. With the certainty that the fight against the weevil 

 must be continued indefinitely, it has become increasingly evident that 



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