Sterility in the Hairy-wing 49c mutant ofDrosophila melanogaster is due to the failure of mature oocytes to pass from the oviduct into the uterus.Patterns of oocyte accumulation in the ovaries, oviducts and uterus of mutant and wild-type flies indicate that ovulation is initiated first by mating and thereafter by the absence of an oocyte in the uterus. While oocyte production is also stimulated by mating, it is maintained by a low number of oocytes in the ovary.Mating also appears to initiate events which cause mature oocytes to deteriorate if they are not soon oviposited.

Histological studies do not permit the distinction between an oocyte, ovary or oviduct malformation as the primary cause of sterility in females homozygous for the Hairywing 49c allele inDrosophila melanogaster. Reciprocal transplantations of larval ovaries between homozygous mutant larvae and normal larvae demonstrate that the sterility is due to a malfunctioning of the oviduct, presumably at the junction of the common oviduct and the uterus. This failure of the oviduct to function normally appears to represent a unique cause of female sterility in this organism.