Magical Fruit Flies

Just as a random bemusing which I wish to send out into cyberspace:
You know those little bugs? Fruit flies maybe? Anyway, they seem to just kind of float around. But the moment you try to catch them they disappear. What's that about? You think they're moving so slow, and you are using your ninja moves, but the fly is gone (soon to return) and your hand is empty. Where the heck do they go?

I'm not sayin', I'm just sayin'.