Research resources are never adequate to conduct tests of such size. It is known by 

 flight-range tests recently conducted by workers at the Mission , Tex, screw-worm 

 plant that the insect will fly 180 miles, and there is evidence from screw- worm case 

 incidences that some migration up to 300 miles occurs. If the importance of the factor 

 of isolation had not been properly appraised in connection with early experiments to test 

 the principle of screw- worm eradication by sterile-insect releases, it is almost certain 

 that the sterile-male method could not have been demonstrated as a practical way to 

 eliminate or control populations of this important pest. 



It is the writer's view that entomologists, generally, have the tendency to under- 

 estimate the distance that insects will spread, and consequently, may not properly 

 appraise the importance of migrating insects in judging the potential value of various 

 control or eradication methods, such as sterile-insect releases, chemical attractants, 

 light traps, or even insecticides. The writer urges that research workers give due 

 consideration to the establishment of proper test procedures to evaluate the impact of 

 control measures on the total population of an insect, whether the method involves the 

 use of sterile insects, or some other system. Experiments to test eradication proce- 

 dures should be conducted on isolated populations of the insect. 



Release of Strains Adapted to the Natural Environment 



Another factor that may be of major importance in achieving the maximum effect 

 of sterile-insect releases is the adaptability of the strain to the environment where 

 releases are to be made. There is considerable evidence that insects reared under 

 laboratory conditions for many generations undergo changes in behavior that may 

 adversely affect their ability to survive and compete satisfactorily with the wild strain 

 in the natural environment in which they are to be released. It is likely that most 

 laboratory strains of insects possess certain behavioral characteristics resulting from 

 natural selection in captivity that could handicap their survival in nature. The 

 Gainesville, Fla. laboratory of the Entomology Research Division undertook a pilot 

 experiment some years ago to determine whether a natural population of the common 

 malaria mosquito (Anopheles quadrimaculatus Say) could be brought under control in a 

 semi-isolated area by the release of gamma-irradiated males. The experiment proved 

 unsuccessful. Subsequent laboratory and field studies indicated that the laboratory 

 strain, reared in captivity for 25 years or longer and through perhaps 200 or more 

 generations, did not readily compete with normal wild males in mating with wild 

 females. This example of failure in the application of the sterile-male-release method 

 cannot be ascribed to a defective principle but rather to the release of a strain inferior 

 to the wild one from the standpoint of competitiveness in the field. 



Many investigators have reported difficulty in establishing new colonies of an 

 insect species that would thrive in the laboratory even though their laboratory-adapted 

 strain was simultaneously developing well under the same conditions. 



It is possible, too, that the environmental conditions under which insects are mass- 

 produced will adversely affect their vigor and competitiveness when released in a more 

 stringent natural environment. 



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