Parthenogenesis in Drosophila mangabeirai Malog.

Meiosis and autogamous fusion has been described for a thelytokous strain of Drosophila mangabeirai in which meiotic spindle orientation differs from the type reported for other species of Drosophila. As a result of this orientation, there is an increased probability for the type of fusion to occur which will produce structurally heterozygous, diploid females. It is suggested that the type of spindle orientation favoring the formation of such individuals is adaptive in nature, since all flies examined are structurally heterozygous diploids, having a relatively high per cent hatchability.