I read a short story in the 80s (as in a read it in the 80s, not that it was written in the 80s) about a protagonist that was bothered by flies, and was unknowingly the demon Beelzebub. Any ideas?
It wasn't the protagonist who was bothered by flies, as it happens, but one of his old friends. The story was set at a college reunion.
Winthrop would never know. Polen was sure of that. He wondered if Casey knew. It would be the supreme joke if Casey did not.
He had run Casey's flies, of course, not that once alone, but many times. Always the same answer! Always the same unpublishable answer.
With a cold shiver he could not quite control, Polen was suddenly conscious of a single fly loose in the room, veering aimlessly for a moment, then beating strongly and reverently toward Beezlebub.