They are worse when it gets really dry. You will notice that after a rain, they are not as bad for a little while. My Parents live in a small block of woods on the Albemarle Sound. For some reason, those flies love that patch of woods and will swarm you 20 and 30 at a time. I have killed 3 in one swat many times there and when You go swimming there, the flies will literally run You down to the water and make You dive in. after that, they leave You alone. Only good thing about those flies is they are fairly easy to kill. Just let him land and come in with Your hand from a side angle. Not dead over its head. They don't seem to see as good out to the sides.CF