Borer Beetle Migration
On their own these guys aren't much of a problem. They do have a stink to them though.
Lonely bug

But they can be a problem when they gather on a wall...
Bugs on wall
... or on a ceiling where they wait to swoop down on any unsuspecting or
suspecting humans to roost in their hair, their clothes and even their mouths.
One year their migration got so bad that they jammed up my fax machine and
somehow (don't ask me how) got inside our bottled water dispenser and proceeded
to add a special indescribable tang to each swallow.

Bugs on ceiling