Hi Bill,

Great shot of a beautiful beastie :)

Although it's always impossible to be 100% sure of ID's from photos, I'd say you're right to call it a Waved Sphinx. The larvae show considerable variations, and, alternatively, yours may also be due to it being in an earlier instar:

http://www.silkmoths.bizland.com/cundulos.htm

and although many don't; some have a red tail too :)

http://bugguide.net/node/view/214518

But what it was feeding on may also be a clue. Ceratomia undulosa prefer ash, but will also take to privet and lilac, according to the top one of those links.

I understand your problems with keeping all of a caterpillar in focus. I've never managed it, especially as I'm stubbornly sticking with natural light ;) However, I've heard that if you want to avoid a black background you can just drape a light-coloured cloth, or something similar behind your subject. Not possible for the more flighty subjects, but definitely worth trying with caterpillars :)

And yes. They won't stop moving because they won't stop eating! Reminds me of a book my daughter used to love: 'The Very Hungry Caterpillar' :)