I'm guessing some of you have been seeing these moths recently, perhaps visiting flowers in your yard? This is a White-lined Sphinx Moth (Hyles lineata).
I've received several reports and questions about them, and yesterday I noticed this one washed up in the wrack line on the beach. (Sometimes that happens to insects — my guess is that they're dispersing but then end up too far out to sea and wash up with the drift.)
This moth was still alive — here it is crawling on my hand:
You can see that this is a medium-sized moth — with a wingspan of ~3.5" (~9 cm) across. That's smaller than the larger silk moths, but larger than many other moth species. Because White-lined Sphinx Moths hover at flowers for nectar, they can be mistaken for hummingbirds from a distance. [Anna's Hummingbirds have a wingspan of ~4.5" (~10 cm).]
Here's another quick photo for scale:
