Answer: First of all, we need to be a bit more specific. We're talking about house flies here, known by scientists the world around as Musca domestica. The house fly associates with people. Virtually anywhere on the planet where you can find people, you will also findMusca domestica.
Anyone who has ever enjoyed a backyard barbecue knows that house flies will crash your picnic table, walk all over your potato salad, and attempt to taste your burger, should you dare to leave it unattended for just a moment. And occasionally, those flies will come to rest on you. So you are probably wondering what they're up to while they sit there. It's a totally understandable concern.
Let's tackle the first bit of this question first