It's a bird... it's a plane...

...it's a sphinx moth!

This sphinx moth is aptly, if somewhat unimaginatively, called the Hummingbird Clearwing (Hemaris thysbe).  Like a hummingbird, it beats its wings rapidly, hovering by a flower for a moment, then abruptly darting off to the next flower. Although the number of legs, the number of wings, the proboscis (the mouthparts, shown coiled in the picture above), the antennae, etc. give it away in a photograph, as it flies, it can easily be mistaken for a hummingbird.

The wings of the Hummingbird Clearwing (Hemaris thysbe) seem to disappear as it hovers.

Even in bright light and with the flash, the wings frequently moved too fast for the camera shutter.  The wings also seem to disappear in the photographs because, as the moth's name suggests, they have large sections that lack scales and are transparent.

A Hummingbird Clearwing (Hemaris thysbe) hovering while drinking nectar from a flower.