Nectaring on Bee Balm (Monarda fistulosa) on 6/22/08.
Snowberry Clearwing Moth (Hemaris diffinis)
It's only taken two years and an astronomical number of deleted pixels to get a halfway decent shot of one of these clearwing moths. I see them every year, though we do seem to have a larger than usual population this year. Seeing them and getting a photograph are two entirely different matters, though. I've never seen one at rest, but always in constant motion as they move from flower to flower.
Adults are said to mimic bumblebees, but except for the coloration, I don't really see the comparison. They feed during the day and are found throughout most of the United States and western Canada.
Thanks to Bobby Grizzard on BugGuide for confirming this ID.
On Slender Mountain Mint (Pycnanthemum tenuifolium) 7/2/08
Sources and Additional Information:
Species Page on BugGuide
Species details from Butterflies and Moths of North America
Images of pinned specimens from Moths of Maryland
Species details from Butterflies and Moths of North America
Images of pinned specimens from Moths of Maryland
