-34- 
In another example equal parts of pyrethrum blossoms and derris 
root --ere mixed with molten naphthalene in the proportion of 3:5 and 
the mixture ground with alumina. Sodium acetate, borax, carbazole, 
thymol, isothyraol, or crude anthracene may be used in place of naph- 
thalene or naphthol. The insecticides obtained according to the pres- 
r.ent invention may also be combined with other insecticidal substances, 
such as arsenic compounds; or with fungicides, such as copper compounds; 
and with adhesives, such as lime-soaps; or with fillers, such as talc, 
alumina, china clay, bole, an: the like. It has been found useful to 
add Turkey-red oil or other salts of sulfonic acids for spraying 
purposes. 
: T ctolophus posticus ( T "alk. ) 
Sonan ( 378 ) in 1927 reported that spraying with derris and soap 
proved very effective against this species infesting tea plants in 
Formosa. 
Nygmia phaeorrhoea (Donov.) (syn., Euproctis chrysorrhoea L. ), the 
bro7/n-tail moth 
" ; eis ( 477 ) in 1931 reported that larvae were killed more quickly 
";hen dusted with Polvo on the ventral side than when dusted on the 
dorsal side. Polvo repelled third instars. 
Van der Laan (243) in 1?35 reported that at 1:5,000, dihydroroten- 
one was less than half as toxic to the larvae as rotenone, and equally 
as toxic at 1:10,000. A solution of rotenone in water (1:1,500) 
lost half its toxicity on 5 hours' exposure to direct sunlight. Dry 
rotenone lost none of its toxicity on 4-2 days' exposure to direct 
sunlight, as determined by the relative toxicity of sprays prepared 
from irradiated and nonirradia'ted rotenone. The same procedure showed 
that dry derris powder lost half its activity when exposed to sunlight 
for 3 days, but retained it much longer after standing 5 days in 
shadow. 
Aqueous suspensions of derris powder, stored in bottles, lose no 
toxicity in 4 to 11 days, but the toxicity is appreciably lower 25 
days after preparation, tin aqueous suspension of derris powder was 
mixed with a concentrated soap solution, allowed to stand 2 days, then 
diluted and sprayed. The toxicity was 20 percent less than that of 
a similar suspension used immediately after preparation or a similar 
suspension that had been allowed to stand 2 days but to which the 
soap was added immediately before spraying. 
Trappmann and Nitsche (417) in 1935 reported that rotenone sprays 
gave 15-percent mortality of last instars after 8 days, whereas roten- 
one dusts had no effect. Dosage was regulated to give a deposit of 
0.18 mg. of rotenone per 500 cm. . 
DeBussy et al. ( 57 ) in 1936 reported that young larvae can be 
controlled by derris dust (rotenone.' 1 percent) but a dust containing 
2 percent of rot' none and 5 percent of ether extract killed only half 
of the older larvae tested. 
