-131- 
on subsurface-feeding larvae it appeared that DDT -was most toxic "when 
applied in colloidal dispersion, less toxic when applied in oil emul- 
sions, and least toxic when applied as dusts*— N* J. Agr. Expt. Sta. 
(276). 
Aedes vexans (Mg.) 
An emulsion of DDT (64 percent kerosene containing 2 percent of 
DDT, 34 percent water, and 0.5 percent sodium lauryl sulfate) applied 
at the rate of 7 gallons per acre [equivalent to 1*16 pounds DDT] to 
a woodland pool gave 90-95 percent control and the effectiveness last- 
ed 4 weeks.— Ginsburg (178 ) . 
Anopheles albiroanus Wied* 
In Panama over 200 tests with heavy dosages of DDT applied either 
as floatable dusts or in oils on the main types of mosquito breeding 
areas were effective for 2 to 6 weeks in heavy growths of Jussiaea , but 
only from 2 to 4 weeks in the more open Naias * Long lasting effects 
depend upon the protection of ihe floating dust or oil film* Under 
river margin conditions, DDT remained effective for a maximum of only 
6 weeks under the most favorable conditions* Dosages of as little as 
0*02 pound of DDT per acre in dust and 0*01 pound per acre in oils or 
emulsion gave perfeot to near perfeot kills of anopheline larvae in 24 
hours* In the use of oils, it was found most satisfactory to use only 
enough oil to cover the area to be treated* Thus 0*05 to 0*025 pound 
of DDT in 1 to 4 pints of used crankcase oil per acre gave better kill- 
ing results than the same amounts of DDT in larger quantities of oil* 
An emulsion concentrate, when mixed with water and applied at the rate 
to give about 0*02 pound of 13DT per acre, gave perfect to near perfeot 
24-hour kills of both anopheline and culicine larvae. This concentrate 
is more difficult to apply and, in concentrations as high as 200 ml. 
per acre, is quite lethal to fish* Comparative tests of paris green-talc 
and DDT-fcalo dusts indicated that the flDT dust was 5 to 10 times as 
toxic to anopheline larvae as the paris green dust. DDT dusts or oils, 
unless used in very heavy doses, were ineffective in controlling culi- 
cine larvae. DDT in emulsion was equally effective against culicines 
and anophelines* Other tests to control adult mosquitoes were also con- 
ducted. DDT in oil was applied by hand sprayers to the ground in jungle 
areas* All mosquitoes disappeared for 1 to 2 days in the quarter- to 
half-acre treated plots. Tests in an open orchard killed mosquitoes 
but infiltration was so rapid that biting rates soon returned to normal* 
Five liters of a 5-percent DDT solution in kerosene, applied with a 
knapsack sprayer, gave nearly complete kill of mosquitoes on a 1-aore 
plot in an open cacao plantation. Checks 48 hours later showed oomplete 
returns to normal mosquito populations.— Gorgas Memorial Laboratory (182) « 
