Observations indicate that matings after the first, do not necessarily result in the 

 deposition of sperm in the spermatheca of the female. This has been noted by investi- 

 gators at the Hawaii Fruit Fly Investigations laboratory in Honolulu and by investigators 

 of the Insects Affecting Man Investigations laboratory at Gainesville, Fla. There is good 

 evidence that in some insects a single mating will fill the spermatheca with sperm, so 

 that subsequent matings will not contribute to the sperm reserve. It may be the rule 

 among polygamous insects that a relatively few matings will fill the sperm reservoir. 

 Even if sperm from several matings are deposited in the reservoir, and if normal sperm 

 and sperm carrying lethal factors mix in the reservoir, the final effect on a total popu- 

 lation should be the same as single matings . 



It has been observed by certain workers that the last mating among polygamous 

 insects determines the source of the sperm that will fertilize eggs of the female. If this 

 is the case, then a polygamous mating habit in an insect species can be an advantage. It 

 would mean that sterile-insect releases can have an immediate adverse impact on the 

 fertility of the adult population that is already present in the environment. For monoga- 

 mous insects, such as the screw-worm, the presence of sterile males will not influence 

 that part of the female population already mated. Thus, the monogamous mating habit is 

 a great disadvantage when female insects outside of an area under treatment with sterile 

 insects can mate with fertile males and then migrate into an area protected by sterile- 

 insect releases. This is a major problem in the current screw-worm program in the 

 Southwest. Females outside of the release zone in Mexico or Arizona may mate with 

 fertile males and migrate for distances of 200 to 300 miles into the area of sterile-fly 

 releases. If the insect were polygamous, and if matings with sterile males would nullify 

 their prior fertile mating, the migrants would pose a lesser threat than they now do. 



Up to the present time, sterile-insect releases have achieved eradication for both 

 monogamous and polygamous insects — the screw- worm and the melon fly. The success- 

 ful eradication of the melon fly from the Island of Rota through the cooperative efforts of 

 the Entomology Research Division, the Department of the Navy, and the Trust Territories, 

 demonstrated that an insect having polygamous mating habits could be eradicated by the 

 sterile-insect-release method. There was no indication that polygamy was a deterrent 

 in the eradication of the melon fly in this pilot eradication program. 



Mating behavior, other than frequency of mating, could however be of great impor- 

 tance in limiting the effectiveness of sterile-insect releases. Probably, the most 

 desirable characteristic is for the released males to disperse to a considerable extent 

 in the search for females. Insects that are greatly restricted in their movement may pose 

 problems of achieving distribution of the released insects in the numbers and places 

 necessary to achieve the desired result throughout the infested area. This could pose a 

 difficult problem in efforts to eliminate populations of the boll weevil by releasing sterile 

 males. This insect, during the regular cotton-growing season, has rather restricted 

 movement. 



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