When my one cat does this, it means we have an invasion of those teeeeeny tiny ants coming in the next 24 hours. There will be nothing where he is looking. NOTHING. But this weirdo can smell them coming or something, because when they do inevitably show up, he starts huffing them, rolling/rubbing on them , and getting high as a goddamn kite. There are no ghosts. My cat snorts ants.