|The wing pattern echoes the feathery antennae motif.|
Enough procrastinating! I spent the evening on it tonight. And after scanning all the "white moths" (2933 moths) and all the moths with a mention of feathery antennae (only 52) on BugGuide, and umpteen more on Google, I gave up and submitted my photo.
Which I should have done to start with, long ago.
The feathery antennae mark this moth as a male. He uses them as a "nose"; they're loaded with olfactory receptors - up to 60,000 in some species. And what he's smelling is a female, emitting her alluring pheromones. Somewhere, maybe miles away.
So sensitive are these organs and so characteristic and powerful is the scent, that a female has been known to summon a male from eleven kilometres away. At such a distance there must be as little as one molecule of scent in a cubic yard of air, yet it is sufficient to cause the male to fly in pursuit of its source. (From AskNature)
UPDATE: The BugGuide people are so quick! The moth is a Phantom Hemlock Looper; Nepytia phantasmaria. Here's a link to a female: note the straight antennae.