Nutrition is one of the most important environmental factors that influence the development and growth in Drosophila. The food composition strongly affects their reproduction, welfare and survival, so it is necessary for flies to search for a mixture of macronutrients that maximizes their fitness. We have five D. melanogaster strains, which were reared for 13 years on five different substrates: standard cornmeal-agar-sugar-yeast medium and four substrates modified by adding tomato, banana, carrot and apple. This study was aimed at determining how such long-term rearing of flies on substrates with different protein content affects fitness traits (dynamics of eclosion, developmental time and egg-to-adult survival). Further, we determined how transferring flies reared on fruit/vegetable substrates to a standard laboratory diet affected their fitness. Results indicate that strains reared on the diet with the lowest content of protein and the highest C/N ratio had the slowest eclosion and developmental time, and lowest egg-to-adult survival (apple diet). The flies reared on the diet with the highest protein content and the lowest C/N ratio had the highest survival (tomato diet). Flies reared on the carrot diet, which is quite similar in protein content and C/N ratio to the standard cornmeal diet, had the fastest development. Transferring flies to the standard cornmeal diet accelerate eclosion and developmental time, but did not affect survival., Jelena Trajković, Vukica Vujić, Dragana Miličić, Gordana Gojgić-Cvijović, Sofija Pavković-Lučić, Tatjana Savić., and Obsahuje bibliografii