In chivalric tradition, they send defiance with their whine. They let you feel their bite and give you an honest chance to retaliate with a well-timed swat. Black flies blunder blindly along en masse, silently, stealthily. They crassly gnaw a hole in your skin and sneak off, leaving the blood flowing. Mosquito bites itch for a couple of days.
Black flies raise welts that itch for a month.
They'll make you crazy. Well, that was what we were up against. It wasn't too bad as long as we stayed out on the water. But camp life took on a tense and defensive edge. We were all in perpetual motion, hoping that, as long as we didn't stand still, the black flies wouldn't be able to keep up with us.