Interspecific Transfer of the "Sex-Ratio" Agent of Drosophila willistoni in Drosophila bifasciata and Drosophila melanogaster

The maternally transmitted "sex-ratio" condition in several species of Drosophila appears to be due to infection by a microorganism of the genus Treponema. Drosophila bifasciata is an exception, since no microorganism has been found in the "sex-ratio" strains of this species. Normal D. bifasciata can be infected by injection of the hemolymph of a "sex-ratio" strain of D. willistoni containing treponemas. The progenies of the infected D. bifasciata, up to and including the F(4) and F(5) generations, have numerous treponemas in their hemolymph. Their progenies are, however, not unisexual, although both females and males are infected. The hemolymph of these D. bifasciata injected in D. melanogaster females causes typical "sex-ratio" symptoms in the progenies of the latter.