Well, consider this from a few dry years:
"Because of the dry, warm conditions this year, there is less running water, so there are actually fewer black flies now than normal, he said."
So I still stand by my statement that they go away when warmer weather is about.
My father was born in the Adirondacks. I have visited there many years as a child, and recently went back for a visit. We always tried to go "after June." The typical season is mid May-June, but can be longer depending on clime. We visited this time in May and the relatives said they were waiting for the warmer weather so the flies would go away.
All but three towns in the Adirondacks quit spraying chemicals because they were killing other insects, including bees. Now they treat streams with B.t.i. I wonder how that is going to fare for the population in a decade or two.
The typical feeding times for the Adirondack Black Fly is early morning or around sunset. They don't feed at night. Only the female bites (that's typical.) They can land numerous times with out biting, but then - watch out. They do not like to be confined and will not enter homes or cars intentionally. If they do they will spend their entire life walking up the screens or window trying to get out.
Wayne MSGT USMC (Ret) & Earlene (CinCHouse)
2008 Winnebago Destination 39W
It is what it is, and then it is what you make of it.