Sexual sterilization of screw-worm flies by the biological alkylating agents, tretamine and thiotepa

Abstract

Tretamine [2,4,6-tris(1-aziridinyl)- s-triazine] or thiotepa [tris(1-aziridinyl)phosphine sulfide] induced sexual sterility in screw-worm flies [ Cochliomyia hominivorax (Coquerel)] when adults were treated by oral or topical administrations and when immature stages were treated by immersion or injection. By oral administration to adults, thiotepa was the more effective chemosterilant, but by topical administration the two compounds were almost equally effective. The survival of screw-worm flies treated with tretamine was often greater than that with thiotepa. When tretamine-sterilized females were mated within a day or two of topical treatment with fertile males, chemosterilant was transferred to the males by bodily contact and reduced their fertility. With topical administration in two equal doses, together constituting a minimum effective dose, the toxicity was slightly reduced, but losses of sterilizing effectiveness occurred. Sterility induced by tretamine or thiotepa in male screw-worm flies, studied by the method of brood fractionation, was irreversible. However, the sexual vigor of males treated with sterilizing doses of these compounds was reduced, since they did not fully compete with untreated males. Chemosterilization of the secondary screw-worm fly [ Cochliomyia macellaria (Fabricius)] is reported for the first time. With C. hominivorax prepupae, immersion in tretamine or thiotepa resulted in the sexual sterilization of the adults that subsequently emerged, but toxicity was very great. With C. hominivorax pupae, immersion or injection resulted in the production of all sterile adults only with thiotepa, but tretamine was not without antifertility activity.