Are Drosophila flies harmful

No, they are not. Drosophila melanogaster (common fruit flies) have been very helpful in genetic research. They are harmless, except that you do not want to take a chance that they will over-run you lab or your home. Also, technically, they are really "vinegar flies", although everyone calls them fruit flies. in other Words, they like to lay eggs on rotting fruit, not fresh fruit like the med fly. thus not a danger to agriculture