Here's the link I looked at, Rosie. The pictures on this link are really nice, and show a lot different body colors and a sort of fan-shaped tail on the hummingbird moths.
http://www.fs.fed.us/wildflowe...
The ones I've seen here are, as I said, the size of the first two joints of my baby finger - really large. They're easily mistaken for a hummingbird, the bird that is, because their wings make a humming sound just like the birds do.
