I just came across your “bug love” page, and thought you might be interested to see this picture. I live in NorthWest Washington, and I have rarely ever seen a moth this size! (That’s why the hand is there, to show how big they are!) This was taken on the 4th of July, 06. I took the picture because they were so big, and it wasn’t till later that I realized what they must be doing!
Your moths are Mating One Eyed Sphinxes, Smerinthus cerisyi. They get the common name due to the hind wings which have “eye spots” that are hidden from view in your photograph.