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factory. In all tests with this chemical the roaches were down in 12 
hours or less, but in many instances were still actively kicking at the 
end of the tests (96 hours) • "When adult roaches were treated in a dust 
settling chamber witn the army louse powder (10 percent DDT) 100 per- 
oent of both males and females were killed in 96 hours. The survival 
time in hours was 5*2 for males and 17*5 for females. Lethane A-70 
roach powder likewise killed 100 percent of both males and females but 
the survival times were shorter, namely 2*4 hours for males and 7.0 
hours for females.— Gould ( 185 ) * 
Laboratory tests with 3, 10, and 25 percent DDT dusts were con- 
ducted against the German cockroach in a settling dust chamber. The 3- 
percent dust gave poor results on both sexes. The 10-percent dust gave 
a 93-percent kill of males in 30 hours and a 66-percent kill of females 
in 55 hours, while the 25-percent dust gave 100-percent kill of males 
and a 98-percent kill of females in the same lengths of time.-- Gould 
(184). 
Deobase sprays containing 0.2 percent of DDT, combined witn either 
pyrethrum, butyl carbitol thiocyanate, or bornyl tniocyanoacetate were 
found to be relatively ineffective when used in the Peet-Grady chamber 
against young nymphs of the German cockroach. When Deobase solutions 
of DDT were sprayed directly on the insects, dilutions down to 0.75 per- 
cent of DDT killed 100 percent of the roaches in 24 hours, but lower 
dilutions did not give oomplete oontrol* Certain types of surface de- 
posits of DDT were found to be very effective against roaohes walking 
aver then. Residues of from 4 to 40 sag* of DDT per square foot de- 
posited by the evaporation of toluene solutions caused no mortality 
within 24 hours, but a deposit of 20 mg* of DDT per square foot, de- 
posited as talo dust, killed 100 percent of the roaohes. An 80 mg. 
deposit of sodium fluoride was required to cause a mortality of 92 
peroent* A deposit of 80 mg* of DDT laid down by the evaporation of 
a solution in Deoba3e-mineral oil gave oomplete oontrol of young 
roaches* Less effective residues were obtained using DDT solutions 
in Deobase, cyolohexanone, or toluene, and also from aqueous sprays 
of a water-dispersible powder* These results indicate that dust de- 
posits of DDT may be much more effective for controlling cockroaohes 
than residues deposited from solutions or suspensions.— Goddin and 
Swingle (179). 
An apartment adjacent to a store was infested with German 
roaches* Cockroaohes were completely eliminated from the apartment 
by blowing a 20 peroent EDT-talc dust into all cracks and crevices 
beneath the linoleum and between flooring wherever openings occurred* 
Other tests with 3 percent of DDT in kerosene against oockroaches 
were not satisfactory* — N* J. Agr. Expt* Sta* (275 ) * 
