Bark lice -- I have gotten numerous calls on this, probably 5 or 6. If I get 5 or 6 calls, you can probably multiply that by 100 to get the real story of how much of this is out there this year.
Bark lice are black bugs that congregate together on the bark of trees. They move as a group and form black blotches on the bark. Not because of the damage they do but because they themselves form the black blotches.
They are not parasites of the tree nor are they something you need to treat for. Why they seem to be more prolific this year is anyone's guess.
Here's a link to Kentucky Pest News featuring an article on bark lice.