Apologies for poor photo. You will need to enlarge and hunt, but it is there. Very long, curved abdomen with dark filament coming out of it with white tip on it.
Unfortunately the image loses resolution when I enlarge it, so I can't see enough detail to know what it is. But going on your description, and assuming it was feeding at the flowers, the most likely candidate is a parasitic wasp of the genus Gasteruption.