16 



INSECT ENEMIES OF THE BOLL WEEVIL. 



A study of Table II, on the mortality due to insects in fallen 

 squares, shows that the principal insect work is that of predatory 

 insects and, furthermore, that the total insect control is, as a rule, 

 less than the eiimatic control. The table embraces the examination 

 of 63,985 weevil stages of which 17,596 were killed by climate, 13,958 

 by predators, and 2,849 by parasites. In other words, the average 

 percentage of control in fallen squares by aU kinds of insects is 26.2 

 per cent, or 21.8 per cent by predators and 4.4 per cent by parasites. 



A further study of Table II shows that the predators have in each 

 year done their most valuable work in the month of August. The 

 parasites, however, have shown considerable variation in the month 

 of their best work. In 1906 the highest average percentage was in 

 October; in 1907 it was in June; in 1908 in November; and in 1909 

 in July. 



Table III. — Monthly mortality of the holl weevil due to insects in hanging squares. 





Squares 

 exam- 

 ined. 



Stages 

 found. 



Stages Mlled by- 



Percentage of stages killed. 



Months. 



Cli- 

 mate, 



Preda- 

 tors. 



Para- 

 sites. 



Total. 



Preda- 

 tors. 



Para- 

 sites. 



All in- 

 sects. 



1906 

 July 



474 



4,165 



2,0.32 



33 



247 



2,566 



1,285 



20 



47 

 539 

 245 



4 



20 

 544 

 269 



10 



76 



337 



125 







57.9 

 55.3 

 49.7 

 70.0 



8.0 

 21.2 

 20.9 

 50.0 



21.0 



13.1 



9.7 







29.0 



August 



34 3 





30.6 



October 



50.0 







Totals and averages for 

 1906 



6,704 



4,118 



835 



843 



538 



53.8 



20.5 



13.0 



33.5 







1907 

 June 



150 



956 



3,543 



88 



513 



2,011 



26 



57 



296 



5 



16 



175 



13 

 103 



580 



50.0 

 34.3 

 52.2 



5.7 

 3.1 



8.7 



14.7 

 20.1 

 28.8 



20.4 



July 



23.2 



August 



37.5 







Totals and averages for 

 1907 



4,649 



2,612 



379 



196 



696 



48.6 



7.5 



26.6 



34.1 







1908 

 July 



2,955 

 1,393 

 3,922 

 1,192 

 1,125 



2,177 

 842 



2,340 



553 



10 



395 

 141 

 476 

 116 



8 



179 

 91 



259 



53 







479 

 279 

 410 

 113 

 



48.4 

 60.7 

 48.9 

 52.9 

 80.0 



8.2 

 10.8 

 11.0 

 10.0 

 



22.0 

 33.1 

 17.5 

 21.2 

 



30.2 



August 



43.9 





28.5 



October 



31.2 



November 











Totals and averages for 

 1908 



10,587 



5,922 



1,136 



582 



1,281 



50.9 



9.8 



21.7 



31.5 







1909 

 January 



80 

 630 

 1,290 

 745 

 136 

 515 



3 



383 

 856 

 496 

 52 

 169 





 36 

 96 

 61 

 14 

 47 







31 



72 



21 







1 







117 

 88 

 76 

 30 

 71 







48.0 

 29.9 

 31.9 

 100.0 

 70.4 





 8.1 



8.4 



4.2 







6 







30.5 

 10.3 

 15.3 

 68.0 

 42.0 







July 



38.6 



August 



18.7 





19.5 





68.0 



December 



42.6 







Totals and averages for 

 1909.. 



3,396 



1, 959 



254 



125 



382 



38.8 



e.4 



19.5 



25.9 







Table III shows that the principal insect work in hanging squares 

 is that of parasitic insects and, furthermore, that the total insect 

 control in hanging squares is each year higher than the climatic 

 control. This table embraces the examination of 14,611 weevil 



