-20- 
Extra 
ft 
Extraction D 
ilution in 
Total K: 
111 afer 24 
No. 
proces 
s gm. of root 
larvae 
hours 
Number 
Percent 
9 
Residue 
from 
1:10,000 
294 
99 
m eter reex- 
20,000 
220 
90 
tracted 
"ith 
40^000 
244 
70 
acetone 
80,000 
251 
27 
10 
Residue 
from 
1: 200 
274 
92 
acetone 
reex- 
400 
292 
90 
tr acted 
T-i th 
800 
229 
92 
^eter 
1,600 
242 
48 
12 
Residue 
from 
1: 400 
232 
94 
alcohol 
reex- 
800 • 
229 
83 
tracted 
with 
1,600 
221 
51 
water 
Check 
qu: 
262 

Culex 
Lnauefasci 
.etus 
Say, the r-on 
.thern house 
mosoui to 
See #«mr>bell et al. (56) under Culex piriens on page 17. 
Badertscher and Wotherspoon (13) in 1935 compared the stabil- 
ity of treated derris and. pyre thrum ponders "ith that of untreated 
powders. Tests were made on several insects, including fourth 
instars of this species. Exposure to a light from a Uviarc mer- 
cury vapor leirro operating on 116 volts ^ith a current of 4.8 
amperes and 450 ^atts for 24 hours destroyed about half the toxic- 
ity of a derris ponder containing 6 percent of rotenone and 18 
percent of acetone extractives. Treated -oowders (treatment not 
described) prolonged the life of these nowders ^hen mi^osed, to 
light. The authors concluded "(l) That derris powder reouires 
at least twice as long as pyre thrum to lose most of its toxicity 
^hen exposed to the action of air anr> sunlight in the summer time. 
(2) Tenet the rapidity of the loss of toxicity in pyrethrum powder 
and in derris powder is largely directly dependent on the intensity 
and duration of the light, (3) That derris povder loses its toxi- 
city relatively much more slowly than does pyrethrum nowder '•hen 
exposed to air in the absence of direct light, (4) That treated 
derris powder after exposure to light and air shows an efficiency 
from 34 to 93 percent greater then untreated derris ponder 
similarly exnosed," 
Eink and Haller (89) in 1935 reported on the relative toxi- 
city to fourth instars of culicine mosquitoes (principally this 
species) of optically active and inactive rotenone derivatives. 
The optically active form? -err more toxic than the corresponding 
optically inactive forms. The order of toxicity was active 
