There's several hundreds of thousands, if not millions of species of fly-like insects. Most of these are local variations that don't differ much from others. The drosophilia melanogaster (which is Greek for "black-bellied dew-friend") has had more genetical experiments happen to it than any other higher life form. AFAIK the hex gene (or hux, or whatever its name was, I keep forgetting that) was first discovered with this species. And experimented with. The results included flies with eyes in their wings and all other similar kinds of things.