Adult diet significantly affected the longevity ofUrophora affinisFrauenfeld andUrophora quadrifasciataMeigen. A diet of undiluted honey supplemented with free water was the most favorable, with both species living for ≈30 d. Flies lived from 12 to 14 d on a honey + yeast hydrolysate (1:1) solution and ≈8 to 10 d on distilled water alone. Flies provided with a yeast hydrolysate + water solution lived 6.2 d, which was not significantly different from longevity of flies provided with neither food nor water (5.6 d). When the yeast hydrolysate concentration was reduced, fly longevity increased. In diet choice preference tests, a significant preference for honey was demonstrated for both fly species when compared with a water + yeast hydrolysate (1:1) solution and a water + honey + yeast solution (1:1:1). Similar results were obtained with diets containing more dilute concentrations of yeast.