There's a lot of seriously wrong stuff in this thread, but your idea about the dangers of crossbreeding different strains of the same species, Gripen, is the most egregiously mistaken, since it contradicts the Biological Species Concept. Now, that concept may be mistaken, but it should at least be acknowledged in a discussion such as this, so that your readers know that youare aware of and disagree with it..
@JCAL: don't you know that biological theories are based on "real life " observation?
@Frogparty: "apterous" simply means "wingless" and can refer to a number of species. It is not the new genus name for D. melanogaster! Also, you are confusing a lab population of homozygous apterous fruit flies with a commercial culture. As you mention, wild flies will contaminate such a culture and they occasionally sneak into commercial cultures, setting up the opportunity for drift to occur, and since the apterous trait only benefits the breeder and not the flies, soon or later, a drift will begin toward the "wild side"!
But there is at least one helpful post here. Rick. of course, is right. Husbandry rules!