Where Do They All Come From?

I think there was a song with that phrase-something about lonely people.  Anyway, that's not what this post is about.  I have been overrun with fruit flies!  I had some a month or so ago got rid of them using the ole vinegar in a coke bottle method and now THEY'RE BACK!  Only in much bigger numbers.  I've been after them with the vacumn cleaner, put all the fruit in the frig, and put out the coke bottle again (that doesn't seem to be very effective this time.)  I'm down to just a few remaining and I'm off to suck up some more!