Okay I'm new at this stuff but what I'd do is find a video of a fly (or bug) shot in high speed (check out user Ultraslo on youtube). As a result of the high speed the background is black. Use a blend mode like screen or multiply or whatever the one is that gets rid of the dark, speed the whole thing up to normal speed, loop it so it lasts longer, make the whole thing to scale with your actor's head, change its position over time in the motion tab...that would work, right?