PHYSIOLOGY, BIOCHEMISTRY, AND TOXICOLOGY Cryopreservation of Embryos of the New World Screwworm Cochliomyia hominivorax (Diptera: Calliphoridae)

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 inßux of cryoprotectants, yields rates of '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 ßies are near or equal to control levels and are available in sufÞcient numbers to reestablish laboratory colonies. Important to the success of this studywas identifying theoptimumembryonic stage for treatment, formulating an incubation regime, which allowed consistent retrieval of embryos at the optimum stage, establishing the correct dehydration time for the previtriÞcation step, and developing a recovery systemafter liquid nitrogen storage of the embryos.