This is a wonderful fly! It has a fly's antennae, of course, and the speckly eyes common in the Eristalinae subfamily of
Syrphid Flies; in all other respects it is an extremely close mimic of a Paper Wasp (Polistes, especially P. dominula).

Why would a fly evolve to mimic a wasp? Could it be a defense mechanism or maybe a means of parasitizing wasps... (?)