Re: What the hell do gnats eat?
Gnats eat Gnits.
And they gather to Gnit-pick.
Seriously, my guess is that on days when the wind is low and temperature and humidity is just right they follow each other's pheremonal scent and gather in clouds for gnat-sex. Those clouds of gnats you fly through while riding your bike or jogging are massive floating orgies.
Think about that while you're picking them out of your teeth and nostrils.