A great deal of research has been initiated by USDA scientists to 
explore the potentialities of the method for certainselect species. Research 
on the release of sterile insects as a means of insect control is under way 
on the Mediterranean fruit fly, melon fly, Mexican fruit fly, oriental fruit 
fly, boll weevil, pink bollworm, codling moth, European corn borer, sugar- 
cane borer, tobacco budworm, tobacco hornworm, fall armyworm, Droso- 
phila fruit flies, gypsy moth, and on several other insect pests and disease 
carriers. 
Success with this technique depends on the following conditions: 
(1) Sexual sterility of the insects must be obtained without serious 
adverse effects on mating behavior. The gamma radiation procedure is 
satisfactory for some insects but it has serious adverse effects on many 
species, such as boll weevils, mosquitoes, gypsy moths, sugarcane borers, 
and other insects. Chemosterilants appear to produce sterility with much 
less adverse effects in most insects, although in some species the com- 
petitiveness of the males after treatment is still greatly reduced. However, 
in general, it appears feasible to produce sterility in most insects either by 
radiation or with chemicals without serious adverse effects on the com- 
petitiveness of the males. 
(2) The insects must be reared in substantial numbers. The numbers 
needed and the cost of rearing them that will permit practical use of the 
sterile insect release method will depend on the circumstances. For the 
elimination of very low level populations which are often difficult to detect 
and destroy, sterile insects may be of great value even though the cost of 
rearing the insects is high per unit number. It is possible, however, to rear 
many insect species on special media by the hundreds of millions or even 
billions at relatively low cost. Screwworms, for example, are raised suc- 
cessfully on a mixture of ground meat, blood, and water. Progress is being 
made in the development of mass rearing methods for a number of other 
insects. 
(3) The sterile insects must be readily dispersible in a manner that 
will bring them into effective competition with normal males. Airplane 
releases of the sterile insects has been an important means of obtaining 
quick and widespread dispersal. 
(4) If the sterile insects to be released are in themselves destructive, 
the number required must not create serious economic losses to crops or 
livestock, or produce excessive annoyance or unjustifiable risks to the 
health of man. 
Until recently the screwworm was the only insect that had been eradi- 
cated in practical operations by releasing sterile insects. However, in 
experiments in 1962 and 1963 on the island of Rota in the Pacific, the 
Department's Hawaii Fruit Fly Laboratory demonstrated that the melon fly 
can also be eradicated by the release of sterile males. The natural popula- 
tion was first reduced by about 75 percent with bait sprays. Then from 4 to 
10 million sterile melon flies were released each week on the 33-square 
mile island. 
The natural melon fly population on Rota began declining rapidly with 
each new generation, as evidenced by the increasing ratio of sterile to 
fertile flies. Within 3 months fruit infestations declined to zero. Thus the 
melon fly is the second important pest that has been eradicated by the 
release of sterile insects. The melon fly is a multiple-mating species and 
its eradication confirms the views of scientists that a monogamous mating 
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