Transformation of Inseminated Females of Aphytis lingnanensis1 into Factitious Virgins by Low-Temperature Treatment

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Abstract
Exposure of adult Aphytis lingnanensis Compere to the low temperature of 30cF for 8 or more hours nearly always caused 100% mortality of sperm in the testes of males and in the spermathecae of mated females, but there were exceptions. However, prolongation of treatment to positively insure complete sperm mortality resulted in excessive mortality of the treated adults as well as excessive reduction in progeny production by the survivors. Different genetic strains had different requirements for the period of cold treatment necessary to cause complete sperm sterilization. Cold-sterilized males of A. lingnanensis were found to display normal courtship and copulatory behavior, but cold-sterilized previously mated females of this species did not accept males a second time, even though normal males were provided. Cold treatment of males apparently had a permanent sterilizing effect. No sperm regeneration whatsoever occurred during the lifetime of the males tested. A pilot test to study the effect of cold treatment on virgin females indicated that none of the previously cold-treated virgin females subsequently were inseminated by the normal males provided, inasmuch as they produced only male progeny. Whether this phenomenon resulted from a lack of sexual receptivity of the cold-treated subvirgin females or whether they became unattractive to males or were otherwise affected is not known. On the other hand, in the control using untreated virgin females, normal insemination and production of female progeny occurred after males were provided. The following possible uses have been suggested for the cold-sterilization technique: (1) mated females of species that are multi-nuptial might be artificially transformed into virgins by this method for use in interstrain or interspecific crosses, provided 100% sperm mortality could be achieved and the females remained psychologically and physiologically suitable for subsequent matings. (2) the technique may be used to sterilize mated females for the purpose of isolating a uniparental strain (females that are capable of reproducing by thelytoklus parthenogenesis) of a hymenopterous parasite from a biparental culture. (3) the technique may be used to maintain a favorable sex ratio in laboratory cultures of parasitic Hymenoptera that exhibit the phenomenon of autoparasitism. (4) possibly the technique may be used as a substitute for irradiation or chemosterilization in methods of insect pest control involving the sterile-male technique or other uses of sterile individuals for population manipulation.