Mutations in the genes ovo or otu can cause abnormal proliferation of XX germ cells, which leads to so-called ovarian tumors, or they can lead to the elimination of XX germ cells, such that adult females possess empty ovaries. Males carrying ovo or otu mutations are unaffected. To find out when this sexual dimorphism affects germ cells, we analyzed the requirement of embryos and larvae for zygotic ovo and otu products. We found that ovo is required for the survival of XX germ cells during larval stages, while XX germ cells lacking otu survive until metamorphosis. Furthermore, we found no sex-transformed mutant larval germ cells and no evidence for an early sex-specific vital process acting in germ cells of the embryo, contrary to what had been suggested earlier.