-15- 
Aedes sp. 
Gi"bson ( 107 ) in 1928 reported .that' under' laboratory con- 
ditions powdered derris root dusted on the surface of water in 
shallow trays at the rate of 15 pounds to the acre of water sur- 
face destroyed larvae in 3 to 22 hours and pupae in from 2 to 
5 days. In a discussion following the reading of this paper 
Ginsburg said: "Last summer [1927] we tested out cube root, 
which is a very strong fish poison. It killed fish in pools 
within 15 minutes but it didn't kill mosquito larvae for 24 
hours, and then only a small percentage of them. The same 
material killed larvae in the laboratory within a few hours." 
Anopheles annularis V. d. Wulp. 
Wats end Singh ( 308 ) in 1937 tested extracts of Derris 
elliptica Benth. , L\_ scendens Benth. , and _D. uliginosa Benth. 
against mosouitoes. Various plants were extracted with alcohol, 
ether, chloroform, or kerosene, end likewise tested; the method 
of Sinton and Wats (Rec. Malaria Survey India 5 (3): 275. 1935) 
was used. Anopheles annularis or A. subp ictus Gressi was used for 
the test insect., One cc. of the undiluted test solution was 
sprayed into the' test chembdr with a No. 15 De Vilbiss sprayer. 
Twenty-five mosquitoes wore introduced into the chamber and 
collected after 30 minutes' exposure. These insects were then 
put into a mosquito cage and placed in a dark room for 24 hours 
under the same conditions as a number of i control insects. The 
results were read immediately after collection to note the 
number of insects flying, and after 24 hours to record the numbers, 
dead and moribund. The results in all cases ^ere much, inferior 
to those with the standard mosquitocide (l cc. of 1-percent 
solution of pyrocide 20 in kerosene) . A crystalline substance, 
m.p. 274-275'' J C, isolated from Derris scandens , was also tested. 
A 40-percent solution of an ethereal extract, . sprayed ihto the 
test chamber before and after introduction of the mosquitoes, 
gave a mortality of only about 60 perpent. The ether-soluble 
parts of derris (containing 5 percent. rotenone) obtained from a 
reliable American firm w?s similarly tested but found to be no 
better. 
Anopheles hyrcanus var. sinensis (Wied.) 
West and Russell ( 315 ) in 1932 reported experiments with 
various toxic substances partially absorbed on charcoal as a 
larvicide for a.nopheline mosouitoes. Rotenone, adsorbed 0.4 
percent on charcoa.1, w £S tested on third and fourth instars. 
of this s-oecies and of Anopheles subp ictus Grassi. A mortality 
of 34 percent was obtained at the end of 24 hours. The authors 
concluded that rotenone en ch?rcoal does not have any greater 
potency than paris green, Hiich is less expensive. 
