BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 31 
Keys to Identification of Troublesome Pests in Alaska Supplied 
Because of the importance of biting midges and black flies to mili- 
tary operations in Alaska, the taxonomy of these annoying pests has 
been intensively studied. Keys and charts to assist in their identi- 
fication have been prepared for publication. 
INSECTS AFFECTING ANIMALS 
New Screw-Worm Remedy Developed 
Recommendations for a new screw-worm remedy were released as a 
result of several years' study at the Kerrville, Tex., laboratory in co- 
operation with the Bureau of Animal Industry. The new prepara- 
tion, designated EQ-335, contains 3 percent of lindane, 35 percent of 
pine oil, 42 percent of mineral oil, 10 percent of silica aerogel, and 10 
percent of an emulsifying agent, EQ-335 is superior to Smear 62, 
the remedy developed by the Department and used extensively and 
successfully by stockmen since 1940. Wounds are adequately pro- 
tected from infestation if the preparation is applied once a week. It 
does not stain wool or clothing, as did Smear 62, and it is less likely 
to deteriorate in storage. Screw- worm flies visiting treated wounds to 
oviposit or to feed are killed by the lindane residue on the wound. 
This feature of the new remedy may prove of particular importance 
in reducing screAV-worm numbers. 
Unique Approach to Screw- Worm Control Studied 
A unique method is under investigation as a possible aid in the 
control or eradication of the screw-worm in restricted areas. The 
method involves the exposure of specially reared flies to X-ra}^s and 
their release among the wild population when this population is at its 
lowest seasonal ebb. It has been demonstrated in the laboratory that 
both male and female flies emerging from pupae exposed to approxi- 
mately 5,000 roentgen rays are sterile, although their normal mating 
behavior is not affected. Of special significance is the fact that female 
screw-worm flies mate only once. Once mated to males made sterile 
with X-rays, normal females will not later mate with normal males ; 
consequently, the eggs they produce are infertile. Adult females 
exposed to X-rays are also sterile. In caged flies of both sexes, X-ray 
sterilized and normal in the ratio of 5 to 1, about 80 percent of the 
normal females produced infertile egg masses. 
Screw-worm numbers vary greatly. In winter the number may 
drop low enough to make it economically feasible to rear, expose to 
X-rays or other radiations, and release the flies in numbers i 
than the number of wild flies. Continued release of sterile flies over 
a period of months might reduce the biotic potential of wild flies to 
the point where control or eradication of the insect could be achieved. 
The practical possibilities of this method of control cannot be esti- 
mated until field studies are conducted. 
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