In this study, the effects of water extract obtained from Cetraria islandica (L.) Ach. Ciwe) on the development of Drosophila melanogaster were investigated. When the different concentrations of Ciwe (0.25; 0.5 and 1.0 mL/100 mL medium) were added to growth medium of adult individuals, no elongation of metamorphosis of F1 progeny was determined. It was observed that the mean number of offspring increased depending on an increase of Ciwe on the application groups. Furthermore, malformed individuals seen in the control group were not observed by adding the different concentrations of Ciwe in the application groups. These differences were statistically signific ant (p< 0.05) according to control group.In this study, the effects of water extract obtained from Cetraria islandica (L.) Ach. Ciwe) on the development of Drosophila melanogaster were investigated. When the different concentrations of Ciwe (0.25; 0.5 and 1.0 mL/100 mL medium) were added to growth medium of adult individuals, no elongation of metamorphosis of F1 progeny was determined. It was observed that the mean number of offspring increased depending on an increase of Ciwe on the application groups. Furthermore, malformed individuals seen in the control group were not observed by adding the different concentrations of Ciwe in the application groups. These differences were statistically signific ant (p< 0.05) according to control group.