-27- 
tests with the powdered devil' s-shoeetringa root gave excellent con- 
trol, lb was indicated that the. plant is a repellent rather than a 
stomach oison. 
F. L. Campbell (60) in 1932 critically reviewed the results of 
Davidson, who found thet rotenone suspended in water It 4.00, sprayed on 
leaves and fed to the . fourth instars as a sandwich, killed all; at 
1:1/X)0, feeding was curtailed. Ten larvae at the beginning of the fourth 
stadium were used, 1 larva to a Petri dish. Each" larva was given an 
apr-le-leaf sandwich {5'/% inch in diameter) containing about 0.002 cc. 
of a 1:1,000 suspension of rotenone, and probably containing about 
0.002 mg. of rotenone. The larvae ate from one-eighth to one- third of 
the sandwiches and therefore probably did not consume more than 0.001 
mg. of rotenone. All but one of these larvae finally died. If ti 
weighed about 0.1 gm., they were killed by doses of about 0.005 mg. of 
rotenone per gram of .body weight.. This calculation is very uncertain, 
but shows that rotenone is much more toxic to tint caterpillars than 
is .acid lead arsenate. Preliminary results obtained by Bulger indicate 
that a dose of at ; least 0.15 mg« of acid lead arsenate per gram of 
body weight of tent caterpillar in the' last inst r is required to kill 
50 percent of a population or, in other ""ords, that the median lethal'-- 
dose is greater than 0,15 nig. per gram. 
Turner ( 418 ) in 1932 reported that cube extract in oil emulsified 
in water with a sulfonated mineral oil (cube extract 1;50,000, oil" 0,5 
percent) killed 62 percent of the half-grown larvae. The check oil 
killed 12 percent. In tests made by Turner in 1929 to determine the 
repellent effect of cube extract, rose plants in the greenhouse were 
sprayed with, emulsified mineral oil containing cube extract 1:25*000, 
Several larvae were placed on each sprayed plant and on suitable check 
plants. In four tests there was much less feeding on the sprayed than 
on the i nsprayed leaves. The larvae failed to grow on sprayed plants 
One spra r ed plant was washed twice in U days bef re larvae were placed 
on it. These larvae grew normally. 
Radertscher and V'otherspoon (l£) in 1935 compared the stability' 
of treated derris and pyrethrum powders with that of untreated powders. . 
Tests were made on the eastern tent caterpillar. Exposure to a light 
from a Uviarc mercury vapor lamp operating on 118 volts with a current 
of 4.8 amperes and ISO watts for 21 hours destroyed about half ~ 
toxicity of a derris powder containing 6 percent of rotenone end 18 
percent of acetone extractives. ?r • s (treatment not <!■ acr~ 
ibed) prolonged the life of t! powders when expose' to light. 
The authors concluded: 
That derris powder r quir a at least twice as lone 
pyrethrum. to lose most of its toxici .: to tl oMon 
of air and sunlight in the summer 
That thQ rapidity o r loss of toxici and d.rris 
powd rs is largely directly : -on th< and dur- 
ation of the light. 
That derris powder loses its toxicity relatively much slower 
than pyrethrum powder wh< n xpos:d to air in tr e abs> ' dir. ct 
light. 
