At the cottage, late May and early June are the worst for the black flies. It would be easy to stay indoors, but there's raking and lots of yard work to be done.
I with an old bucket hat, and some left over wedding toule, I fashioned a hat sort of like a bee keepers hat. I made two. With the excess veil tucked into the front of my sweater, and wearing long pants and gloves, we got to work.
The veiled bucket hats worked great. The black flies warmed like crazy while we raked an trimmed trees. But not one found their way inside the veil.