An excess of females in progenies is commonly referred to as sex-ratio (SR). In this report, we describe three new occurrences of SR in species of the tripunctata radiation, Drosophila neocardini, Drosophila ornatifrons and Drosophila paraguayensis. Repeated backcrosses with males from normal strains were used to maintain the SR strains in the laboratory, always with all-female broods. The egg-larva viability of the SR strains was approximately half that of a normal strain, and antibiotic treatment restored the production of males in SR strains. PCR screening with Spiroplasma-specific primers showed that only SR strains tested positive for Spiroplasma. The results showed that in the three species, SR was maternally inherited and involved ea...