No matter what Yeats says, the paired turbulences of air lifting living wings have more worth than all the gold in Byzantium.
It’s not an omen or a emblem, it’s an an insect. It has nothing to do with (for instance) hope. There’s a reason why the sermon is no longer a living literary genre. But
The vehicle of the metaphor, 1934:
A tenor, eternally recurring:
Meanwhile, far below, the musicians tune up for the last dance, which (for the convenience of the men of first class who will shortly be boarding the lifeboats) is to be held en travesti. Letter to the editor, New York Times 4 August 2016:
It is time for responsible Republicans to abandon the sinking ship into which Donald Trump is poking holes and set about fine-tuning their primary system to prevent this travesty from happening again.