Circular 21 - Insecticides and SubsiiLary Materials 26 
Derris powder, and a similar material, 
cube powder, are prepared by grinding finely 
the roots of certain tropical plants which 
contain several toxic ingredients of which 
rotenone is the most important. Good grades 
of derris powder contain from 4 to 5 percent 
of rotenone and about 3^ times that quantity 
of total extractives. It is usually ground 
sufficiently fine that most of it will pass 
a 200 mesh screen. 
Caution ; Dusts and powders made from 
derris and cube are not considered poisonous 
to man, but when inhaled the dust causes mild 
irritation and a slight paralytic effect in 
the tongue and throat. They are also somewhat 
irritating to the pubic regions. 
Derris powder containing 5 percent 
rotenone may be purchased in barrel lots at 
prices ranging from 28 to 30 cents per pound 
f .o.b. New York City,. 
For manufacturers and distributors see 
numbers 3, 35, 72, 79, and 113 of list at end 
of this circular. 
DIATOH'IACEGUS EARTH 
Diatomaceous earth (infusorial earth) 
may be used as a carrier in various insecti- 
cidal dusts, especially for paris green in 
the control of mosquito larvae which carry 
malaria. The dust is usually mixed at the 
rate of 4 or 5 parts of the earth to 1 of 
paris green. 
