In this study, the effects of water extract (Ule) obtained from the lichen species Usnea longissima Ach. on Drosophila melanogaster was investigated. For this purpose, different concentrations of Ule (0.5; 1.0; 1.5; 2.0 and 2.5 ml/100 ml medium) were added to the growth medium of adult individuals. Comparing the development stages of F, and F, of first three application groups (0.5, 1.0 and 1.5) to that of control group, we found that four groups completed this stage at the same time. The latter two application groups (2.0 and 2.5) showed a delay compared to that of control. The number of total offsprings was increased with the first three concentrations. While it was decreased with the last two concentrations, and various phenotypic abnormalities occured in the last two offsprings.