Cryopreservation of embryos of the new world screwworm Cochliomyia hominivorax (Diptera : Calliphoridae)

A method for cryopreserving embryos of the screwworm, Cochliomyia hominivor ax (Coquerel), was developed for the long-term storage of strains used in r esearch projects and for colonies maintained as back-up to production strai ns that are mass-reared for sterile insect release programs. This protocol, when combined with a previous procedure that was designed to render screww orm embryos permeable to water loss and the influx of cryoprotectants. yiel ds rates of approximate to 53% hatching, 22% pupation, and 75% adult emerge nce. These yields are all lower than control levels. but by the next genera tion the progeny of the cryopreserved flies are near or equal to control le vels and are available in sufficient numbers to reestablish laboratory colo nies. Important to the success of this study was identifying the optimum em bryonic stage for treatment, formulating an incubation regime, which allowe d consistent retrieval of embryos at the optimum stage, establishing the co rrect dehydration time for the previtrification step, and developing a reco very system after liquid nitrogen storage of the embryos.