-25- 
•Dractically no effect on the red s-nider, end "hen the pyrethrins " T ere 
increased to 2 percent, a relatively hi^h concentration, the mortality 
'"as only 9.52 percent. The addition of 0.5 percent of rotenone to the 
1.5 percent of pyrethrins killed 37 -percent of the red solders "hich is 
poor control "but indicates an increased toxicity of 35 percent due to 
the rotenone. One percent of pyrethrins end 1 percent of rotenone com- 
bined caused an average mortality of 79.65 percent; end 2 percent of 
rotenone without pyrethrins killed 87.16 percent of the red spiders and 
was the most effective formule used in this series. S-nrey mixtures con- 
taining "other extracted resins" of derris were .-pproximetely one-half 
es toxic to the red spider as was rotenone, and when used at t^ice the 
concentretion produced en equal or slightly greater mortality of this 
pest. A summary of results is es follows: 
Pyrethrins 
Other derris resins 
Percent 
Percent 
Percent 
1.5 
0. 
1.0 
1.0 

2.0 

0- 
4.0 
. . 1.5. 
o. 
0. 
2.0 
0. 
0.- 
1.5 
0, 
5 

1.0 
1. 


. 
2. 


Avere^e mortality 
of the red slider 
Percent 
62.24 
84.25 
86.77 
1.81 
9.52 
37.09 
79.65 
87.16 
