NATURAL CONTROL. 



145 



Table LXIV. — Weighted average insect control of immature stages of the boll weei il, by 



months. 



Month. 



Forms ex- 

 amined 



Stages 

 found . 



Killed 



by par- 

 asites. 



Per- 

 centage 



killed 

 by par- 

 asites. 



Killed 



by 



preda- 

 tors. 



Per- 

 centage 

 killed 



by 

 preda- 

 tors. 



Per- 

 cent ace 

 killed 

 by all 

 insects. 



January... 

 February. . 



March 



May 



June 



July 



August 



September. 

 October. . . 

 November. 

 December . 



Total 



Weighted average. 



5,087 

 13,597 



2,500 

 100 

 16,930 

 43, 059 

 80,923 

 37,378 

 17,344 



2,534 



2,663 



,285 

 665 

 159 

 56 

 ,708 

 ,758 

 ,170 

 ,107 

 ,283 

 798 



54 



56 



2 



2 



553 



536 



,970 



,160 



879 



127 



63 

 60 



28 

 



'.IV i 



247 

 248 



495 



77:: 

 2 

 14 



4.90 



9.02 

 17.61 

 .00 

 18.57 

 1 4. 92 

 24 86 

 20. 43 



9.33 

 .25 



2.03 



9. 10 



17.44 

 18.86 

 3. 57 

 23. 73 

 21.97 

 30.79 

 27. 21 

 19.94 

 16. 16 

 13. 94 



222, 715 



94, 677 



17,919 



6.78 



18. 92 



The weighted average insect control in June, July, August, and September proves to be 26.82 per cent 

 and for the remainder of the year 17.11 per cent. 



A few records of high insect control will suffice to illustrate the 

 extent of control under some conditions. 



Table LXV. — Highest records of insect control of the boll weevil. 



Date. 



Location of 

 squares. 



Stages. 



Killed by 

 insects. 



Athens, Tex 



Hallettsville, Tex 



Overton, Tex 



Athens, Tex 



Beeville, Tex 



Victoria, Tex 



Beeville, Tex 



Arlington, Tex.. . 

 Cuero, Tex 



Aug. 

 Aug. 

 Aug. 

 Aug. 

 Aug. 



1,1907 

 1,1908 

 1,1906 

 1,1907 

 1,1906 



July 29,1908 

 Sept. 1,1906 

 July —,1909 

 June 20,1908 



Fallen... 

 ..do.... 

 ..do.... 

 Hanging 

 Fallen.. 

 ..do.... 

 ..do.... 

 Hanging 

 Fallen... 



255 



100 



197 



75 



1,310 



375 



678 



55 



549 



Per cent. 

 96.11 

 92. 00 

 85.20 

 84.00 

 78.80 

 78.38 

 77.40 

 75.44 

 73.60 



The distribution of insect control in the four principal classes of 

 forms, and also by geographical sections, has been presented in the 

 general discussion of natural control. 



BIRDS. 



Exhaustive studies of the stomachs of many birds killed in infested 

 cotton fields by the agents of the Biological Survey of this depart- 

 ment have emphasized the fact that the birds play a considerable 

 part in the control of the adult boll weevils. This investigation has 

 resulted in a list of 53 species which more or less commonly feed upon 

 the adult weevils. In Cuba, Mr. E. A. Schwarz discovered that an 

 oriole (Icterus hypomelas) has developed a habit of extracting the 

 immature stages from the bolls and squares. 



Table LXVI, which follows, is taken from Circular 64 of the Bureau 

 of Biological Survev. 



28873°— S. Doc. 305, 62-2- 



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