A method for cryopreserving embryos of the screwworm, Cochliomyia hominivorax (Coquerel), was developed for the long-term storage of strains used in research projects and for colonies maintained as back-up to production strains that are mass-reared for sterile insect release programs. This protocol, when combined with a previous procedure that was designed to render screwworm embryos permeable to water loss and the influx of cryoprotectants, yields rates of approximately equal to 53% hatching, 22% pupation, and 75% adult emergence. These yields are all lower than control levels, but by the next generation the progeny of the cryopreserved flies are near or equal to control levels and are available in sufficient numbers to reestablish laboratory colonies. Important to the success of this study was identifying the optimum embryonic stage for treatment, formulating an incubation regime, which allowed consistent retrieval of embryos at the optimum stage, establishing the correct dehydration time for the previtrification step, and developing a recovery system after liquid nitrogen storage of the embryos.
