The widely held scientific belief that females of all species generally outlive their male counterparts may not hold true and is certainly not valid for Mediterranean fruit flies, according to the findings of a UC Davis entomology professor. Insect demographer James R. Carey uses the fast-breeding Medflies to examine theories about lifespans. In a longevity study of 1.2 million Medflies, Carey found that young male Medflies were at a lower risk of dying than were females. But female death rates began to decline during mid-life and by the advanced age of 60 days -- equivalent to 85 years in humans -- the chance of dying was equal for both males and females. Among the extremely old Medflies, females had lower death rates. "These results indicate that there is not a universal law in male/female longevity," says Carey, who reports this "crossover" longevity phenomenon in the cover article of the January issue of the Journal of Animal Ecology. "Furthermore, it is impossible from this study to classify either sex as more robust or longer lived, since longevity varied according to the flies' environment and treatment."