You're walking in the woods or a field and there's a damn biting fly buzzing around your head. It keeps trying to land on your head and you know if you let it, you'll feel a painful chomp.  Those flies are almost malicious in the way they'll follow you around as you're walking. They're evil . These flies are known as deer flies. You've seen them before when you occasionally managed to catch one as its biting you. It turns out, it's not easy to get rid of them. You can't just put...