- 1-6 - 
temporarily so in another. In a third house a 75-porcGnt dust was only 
moderately efficient; in a fourth test a 50-porccnt dust was inefficient. 
Flour was used as a diluent. 
Davidson concluded that dorris powder is a remedy of vclue, "but it 
would appear that two or more applications are necessary and that it loses 
its efficiency if diluted more than 25 percent. It acts on larvae and c.dult 
m.itcs "by stupefying them, the insects dropping to the gro^ond and dying after 
2 or 3 days. The matcria.l is rather unpleasant to apply. 
A commercia,l extract of dorris, 16 percent, diluted to 1 to 1,000 
and 1 to 500, with the addition of whalo-oil soap, 4 pounds per 100 United 
States gallons, was inefficient. 
De Ong and irhite (26) in 1924 reported the results of tests '^ H. E. 
T'/oodworth with species of derris from the Philippines as follov;s; 
Scientific nrme 
Derris elliptica 
Derris philippinensis 
Derris sp. 
Dilution 
Parts used 
of 
solution 
Hemarks 
stem 
20fo 
negative 
young shoot 
20fo 
negative 
root 
2<yfo 
positive 
leaves 
2Cffo 
negative 
stem 
1^ 
por^itive 
stem ("boiled) 
20fo 
negative 
roots 
20^0 
positive 
lea.vcs 
20fo 
negative 
stem 
20fo 
positive 
flowers 
lOfo 
negative 
leaves ("boiled) 
20fo 
negat ive 
The insect used in those tests "by I'Joodwbrth is not given. 
Dc Ong and VJliito reported the results of their own tests with derris 
as follows: 
The CO miner cia.l extract of 16 percent concent ra.t ion 
diluted 1 to 500 gave a 13-pcrccnt control on Aphis nerii Pons., 
and a 50 percent control on the green peach aphid, Myzus persicae 
Sulzer. Dilutions of 1 to 300 gave a maximum control of 68 per- 
cent on the latter species of aphid and 25 percent on the red 
spider, Tetranychus telarius L. Dilutions of the same con- 
centrate at 1 to 500 added to mosquito-infested water killed 
65 percent of the larvae "but hp.d no effect on the pupae. 
The pov.'dered derris root (undiluted) sprinlcled on the surface 
of the water killed 90 percent of the iarvae in 2 to 4 hours. 
The same pov/der when dusted on aphids gave a 100 percent 
efficiency in 8 hours and a 98 percent control of the larvae 
of Euphyaryas chalccdona Ehldy. and Hew. when dusted on the 
leaves upon vjhich they were feeding. From these experiments it 
is Judged that dorris is "both a stomach and a "respiratory" or 
tracheal poison. The reaction on the caterpillars must have 
resulted from ingestion of the pov/dcr, since fiimigating tests with 
the material gave negative results. 
