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The early history of DDT as a mosquito control agent has been 
sketched by Stage (330 ) . In laboratory tests a dosage equivalent to 
only 1 pound of DDT to 250 acres of water surface was completely effec- 
tive against full-grown larvae of Anopheles quadrimaculatus Say. DDT 
was toxic as a dust to 62 percent of these larvae when applied at the 
rate of 0.0001 pound per acre. As a suspension at 0.01 p.p.m., it 
gave practically 100 percent mortality in 48 hours, being more than 
100 times as toxic as phenothiazine. In the field a spectacular kill 
of mosquito larvae was observed when a mist spray containing 9.5 quarts 
of 5 percent DDT in fuel oil was dispersed from a decontamination 
cylinder over nearly 2 aores of Pontederia swamp. This application, 
at the rate of 0.15 pound of DDT per acre, gave perfect control over 
the entire swamp area} i»e., for a distance of 600 feet from the point 
of application. Although DDT is stable and long-lasting, certain fao- 
tor3 limit the duration of its residual action when it is applied in 
dusts to water surfaces. Research conducted in unprotected breeding 
areas showed that wave action, wind, and water movements cause shift- 
ing of surface films of DDT dust, wito. a consequent loss in effect 
shortly after application* In quiet pools where the vegetation is 
dense, effective control of anophellne breeding has been obtained for 
a period of 4 to 8 weeks when DDT dusts have been applied at the rate 
of 1 to 2 pounds of DDT per acre. Very little progress has been made 
in determining the action of dusts. Because of its extreme toxicity 
when taken internally and because of the feeding habits of the larvae, 
it is presumed that DDT in a dust kills primarily as a stomach poison. 
Tests with petroleum oil solutions at remarkably low dosages have 
demonstrated satisfactory control of Anopheles larvae. The effective 
amount of DDT in petroleum oils is essentially the same as when applied 
in dust form. As little as 1 quart of oil per aore of water surfaoe 
gives high kills when reinforced with 5 percent of DDT. In fact, the 
size of the dosage is limited greatly when. DDT is applied with exist- 
ing spray equipment because of the difficulty of spreading the email 
volume of larvicide evenly over the water. Flowing water has been 
successfully treated with DDT by means of drip cans. The usefulness 
of DDT as a larvicide is not limited to anophelines. It is also very 
effective against culicine mosquitoes. In suspensions, dosages of 1 
p.p.ro., or higher, show residual toxicity to species breeding in rain 
barrels. In field applications suspensions and emulsions of DDT were 
more generally effective against the fresh-*water and salt-marsh culi- 
oines than was DDT as a surface application in dusts or oil solution. 
Dosages as low as 0.05 p.p.nu were effective against Aedes ta eni orhynohu s 
Wied., A. sollicitans (Walk.), A. aegypti (L»), Psorophora confinnis 
L. Arr., P. ciliata F., and Cul"ex quinquefasciatus Say. 0*n the basis 
of this work, Busman and Longcoy in 1943 designed spray equipment for 
light planes which dispersed a 5- to 10-percent solution of DDT in fuel 
