BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 6 
chlordane, and gamma benzene hexachloride all showed promise, 
although certain strains of flies highly resistant to DDT also showed 
some resistance to these insecticides. 
Aerial Applications of DDT Kill Mosquitoes and Black Flies 
Aerial applications of DDT gave excellent control of mosquitoes 
and black flies. In Alaska several areas comprising up to 30,000 acres 
were treated at the rate of 0.1 pound of DDT per acre. Both larvae 
and adults of Aedes and Culiseta mosquitoes were killed. Mosquitoes 
in Alaska are unusually strong fliers, however, and several sprayings 
during the season were necessary to give protection against those 
flying in from untreated areas. Black fly larvae in streams were also 
killed by this treatment. A single passage of a C-47 airplane spray- 
ing an 800-foot swath across a stream gave complete control of these 
larvae for a distance of 2!/2 miles below the place of application. 
Experiments were continued with applications of DDT to mos- 
quito-breeding places before snowfall. In Oregon good control of 
mosquitoes was obtained with 0.5 pound of DDT applied at this time. 
In Arctic areas treatments before snowfall and applications to the 
snow killed larvae hatching in the spring, but results were erratic when 
dosages less than 0.25 to 0.5 pound per acre were used. In compara- 
tive tests more dependable control at lower dosages was obtained when 
applications were made after the eggs had hatched. However, repeated 
applications of DDT against adults over mosquito-breeding areas left 
sufficient deposit to cause a marked reduction of larvae the following 
season. 
Observations in Pennsylvania after aerial spraying with DDT for 
gypsy moth control showed that black flies were killed by the treat- 
ment. 
New Chlorinated Hydrocarbons as Effective as DDT Against Flies 
and Mosquitoes 
Several new chlorinated hydrocarbon insecticides have been tested 
in the laboratory to compare their effectiveness against mosquitoes and 
house flies with that of DDT. Heptachlor and a compound known as 
118 were about as effective as DDT against larvae of the common 
malaria mosquito and several species of Culex and Aedes, but less 
effective against adults of the yellow-fever mosquito. Another com- 
pound, known as 497, was two or three times as toxic as DDT to both 
larvae and adults of all these species. When tested against house flies, 
all three of these compounds were much more toxic than DDT when 
employed as space sprays, and one of them (497) also showed consid- 
erable residual effectiveness. Further work is under way with these 
materials. 
FABRICS PROTECTED AGAINST DAMAGE BY INSECTS 
DDT has been found to give excellent protection to woolen fabrics 
and certain other animal products, such as feathers and bristles, against 
damage by insects. Woolen cloth impregnated with as little as 0.25 
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