The Induction of Sexual Sterility in the Screw-Worm Fly by Antimetabolites and Alkylating Agents1

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Abstract
Twenty-nine antimetabolites and alkylating agents were studied as sexual sterilants of the screw-worm fly (Cochliomyia hominivorax (Coquerel)). The antimetabolites included analogues of folic acid, glutamine, purine, and pyrimidine; the alkylating agents included nitrogen mustards and aziridinyl derivatives. Flies less than 24 hours old were treated topically by application of microliter quantities of chemosterilant solutions to the cuticle, or orally by providing food containing chemosterilants. The effectiveness of these antifertility agents was judged by the number and hatchability of eggs from treated flies as compared with those of eggs from control flies. By topical application to both sexes, 12 compounds sterilized screw-worm flies. These compounds were a glutamine antagonist, two nitrogen mustards, and nine aziridinyl derivatives. When the separate effects of topical treatments on each sex were tested, the glutamine antagonist and three aziridinyl derivatives sterilized males only, and the two nitrogen mustards sterilized females only. Three other aziridinyl derivatives eliminated fecundity or hatchability when either sex was treated. Of the topically tested chemosterilants in this series, tretamine sterilized either sex independently with the lowest toxic effects. By oral treatment, 26 compounds incorporated into the daily diet of both sexes for 1 week sterilized screw-worm flies. These compounds included 9 antimetabolites, 2 nitrogen mustards, and 15 aziridinyl derivatives. Fourteen of these chemosterilant, which were completely effective when fed to both sexes only during the first 24 hours following emergence, and tretamine were studied further with respect to the effect of the ingested chemicals on each sex. Two folic acid and two pyrimidine antagonists sterilized females only. Eight aziridinyl derivatives sterilized males, and four of these sterilized females as well. Bis(1-aziridinyl)morpholinophosphine sulfide and 1,1′-sulfinylbis(2-methylaziridine) permitted the greatest survival of flies.