We have black flies here too, they are horrid. Good thing they don't last long, at least here. When I have to work outside, I wipe my face with apple cider vinegar. My neck, ears and entire hairline as well. It really does work. I smell like a pickle though :)
Those black flies are an awful pest, this is a link on what to look for and do about them:
https://getridofthings.com/get-rid-of-black-flies/
Sometimes it just comes down to protective clothing.
For mosquitoes:
https://endmosquitoes.com/how-to-get-rid-of-mosquitoes-in-yard-naturally/
It is remarkable how the black flies need moving water to lay their eggs and just to opposite for mosquitoes.
There tips may help:
https://blog.mosquito.buzz/how-to-deal-with-black-flies
We have black flies here too, they are horrid. Good thing they don't last long, at least here. When I have to work outside, I wipe my face with apple cider vinegar. My neck, ears and entire hairline as well. It really does work. I smell like a pickle though :)