ECONOMIC ZOOLOGY ENTOMOLOGY. 757 



Study of the various natural a;,'i'iick'S will serve as a Itasis for artilicial means 

 of combating this pest. The author, iu studying these various factors, directed 

 chief attention to determining as accurately as possible the relative influence 

 of each factor. 



The boll weevil has been found capable of considerable adaptation to condi- 

 tions of temiH'rature and humidity. It appears, however, as a result of observa- 

 tiou and experiment that with the presence of a fair amount of moisture in the 

 soil until the s(piares begin to form and a following period of hot dry weather 

 for 4 to weeks, the boll weevil may be expected to be considerably checked. 

 A continuous di*y season is likewise unfavorable to a multii)lication of the 

 weevils, but also badly affects the cotton crop. The boll weevil is considerably 

 reduced by the occurrence of changeable weather with frequent low tempera- 

 tures and rainfall in winter. The defoliation of cotton by leaf worms may 

 result in depriving a number of weevils of sufficient food late in the season. 



About 70 per cent of the weevils developed in the field are found iu fallen 

 forms and the mortality among such weevils is much greater than in those 

 which remain in hanging forms. The factors of natural control operate more 

 effectively against weevils iu squares than against those in bolls. Particular 

 attention was given to a study of the agency of an ant belonging to the species 

 SohiwiJsis gcminata in the control of the weevil. In this work more than 86,000 

 forms were examined. It is believed that the ant iu question is of more im- 

 portance iu the control of the weevil in summer than are heat and parasites 

 combined. The ants appear to enter only those forms which contain living 

 stages of the weevil. All of the parasites which attack the boll weevil have 

 other hosts and do much more effective work in hanging than in fallen forms. 



The degi-ee of benefit obtained from natural control was found to be highest 

 in southern Texas and lowest in the southwestern part of the State. In combi- 

 nation with natural means of control, cultural methods should be adopted which 

 will hasten the maturity and increase the yield of the croi). 



Studies of parasites of the cotton boll weevil, W. D. Pierce {V. 8. Dcpt. 

 A(jr., liur. Eiit. BuJ. 13, pp. 63, pJx. J. fl(j.-^. 6). — At present parasites are not con- 

 sidered one of the most imi)ortant factors in the control of the boll weevil, but 

 it is believed that their importance may be considerably increased by the adop- 

 tion of practical methods of encouragement. Fifteen species of insects are 

 known to prey upon the immature stages of the cotton boll weevil. These para- 

 sites are native to this country and have been known for some time as parasites 

 of other species of weevils within the territory infested with the cotton boll 

 weevil. Some of the weevils other than the cotton boll weevil are quite effect- 

 ively held in check by the parasites. The distribution of the weevils related to 

 the cotton boll weevil varies greatly according to species. 



It is urged that the information thus far obtained relating to the life history 

 of weevil parasites may be utilized in controlling the boll weevil by propagating 

 and collecting the parasites and by eliminating related weevils, thus forcing the 

 parasites to attack the boll weevil. .The bulletin contains a detailed account 

 of work done in the study of weevil parasites in lOOG, including the breeding 

 lecords, conditions favorable for parasitism, tield conditions, geographical dis- 

 tribution, propagation of parasites, and the study of the souri-es from which 

 jjarasites may be obtained. The exact conditions which bring about instances 

 of excessive parasitism are not thoroughly understood. Some of the factors 

 of the problem, however, are to be sought in relative moisture and light, resist- 

 ance of plants to weevil injury, and abundance of other species of weevils iu 

 the vicinity of infested cotton. Experiments on a small scale in releasing para- 

 sites have been found to increase the extent of parasitism. This method will 

 be tried on a large scale. 



