-28- 
That treated derris- ponder after exposure to light and air 
shows an efficiency from 34 to 93 percent greater than untreated 
derris powder similarly exposed. 
Felt and Bromley ( 126 ) in 1937 reported the results of tests made 
in 1936 with several brands of pyre thrum powder and cube powder applied 
in a mixture of, summer oil 1:200 as contact insecticides. In general, 
results on expbsed tent caterpillars were better than on cankerworms. 
One or two commercial brands of derris powder gave excellent kills of 
exposed +"-ent caterpillars at the rate of 3 pounds of 4-percent powder 
to 100 g lions of spray. The cube powder appeared slightly less toxic, 
requiring larger amounts of material. The pyre thrum powder in the oil' 
emulsions was invariably less toxic than the pyrethrum-extract soap 
sprays and less toxic to the older tent cater illars than was the 
derris. 
Derris-gypsum dusts containing 5» 12. 5» and 25 percent of derris 
(4 percent rotenone) in laboratory tests caused mortalities of 0, 28, 
and 92 percent, respectively. — Kelsall and Stultz ( 234 ) in 1937. 
Hamilton ( 180 ) in 1938 reported that the larvae on wild cherry, 
apple, and hawthorn trees were satisfactorily controlled by a spray 
of cube or derris powder (4 percent rotenone) at the rate of 4 pounds 
per 100 gallons of spr^y plus 4 pounds of rosin-residue emulsion. The 
spray, acts as a contact poison and as a repellent. The effective 
period is 6 to 8 days. Caterpillars would not feed on sprayed foliage. 
These results were referred to by the New Jersey State Agricultural 
Experiment Station ( 294 ) in 1938. 
Felt and Bromley ( 128 ) in 1940 reported that cube dust was effec- 
tive against very young eastern tent caterpillars in southwestern 
Connecticut in the spring of 1939. 
Malacosoma disstria Kbn., the forest tent caterpillar 
A. 5 or 6-year old sample of .derris was ineffective when dusted 
or sprayed on chokecherry foliage fed on by the caterpillars. — Kelsall 
et al. ( 233 ) in 1926. 
IV^'la cose via neustria (L. ) 
The larvae were used as a test insect by Fryer et al. ( 149 ) in 
1923 in evaluating derris •preparations. 
Spoon and Van der Laan (j8£) in 1935 described tests with various 
samples of powdered derris root to determine whether the rotenone 
content or the total ether extract is the better means of judging the 
quality. The; materials w re dusted and sprayed on the caterpillars 
of several species, including the lackey moth. The rotenone content 
oh the 10 samples of derris root ranged from to 8 percent; and the 
total ether extract from 8 to 23 percent. v hen applied as a spray 0.1 
percent of kgr&l was added as a spreader. It was concluded that the 
■ bher extract is not a sufficient indication of the biological value 
ri.s roots. \ good indication, however, is obtained from a con- 
sideration of the rotenone content as obtained by the extraction-crys- 
