Directional selection and heritability for pupal weight in the screwworm, Cochliomyia hominivorax (Diptera: Calliphoridae)

Two factory production strains of the screwworm, C. hominivorax (C.), were subjected to directional selection for increasing or decreasing pupal weight at 4 days. After seven or eight cycles of mass selection, average pupal weight increased from 50 mg to 75 to 80 mg in heavy pupae lines, with heritabilities of ca. 0.60. In the light pupae lines decreases of ca. 5 mg were realized, with heritabilities of ca. 0.15. Pupal weight was positively correlated with development time, egg mass size, body length and width, and wing area. A mark-release-recapture experiment indicated that heavy and normal-sized flies dispersed and survived about the same.