Fruit Flies and VBS

What a combination for a post, eh?
I have a question.
Where in the world do fruit flies come from? I mean, how do they know the precise moment my bananas are getting a little too ripe? Or that there are grapes on my counter? Or that we just bought a watermelon?
Surely they don't live in my house just waiting some yummy fruit, do they??
What I really want to know is...does all fruit have little fruit fly maggots that only turn into flies when the fruit gets ripe? Are we eating fruit fly larvae everyday??
Does anyone know?? Because it really has me perplexed!

We got the "stuff" for VBS today. It is just a CD rom with all the materials on it and ready to be printed out. I was unsure at first, how well it would work, but I'm hoping we can swing it. I'm disappointed with the music(or lack thereof, there are only 2 songs!!!) and the fact that everything says VBS 2003. No where did it mention the fact that the materials would have 2003 on them!! Since it is all printable, we are working on seeing if we can photoshop that out of there. Please pray that it works, otherwise it could be a royal pain.
Other than that, I really think it is doable. Of course, VBS is always doable, it's just a matter of whether or not I am able to be a director! This is all new territory for me....so wish me luck!!