Yuck!
Everytime I open my compost bin to add material I get a face full of small flies. Is there something I can add to get rid of them or are they collaterally beneficial?

If you look closer you will see maggots, grubs, cockroaches, ants, worms, mosquitoes, gnats, fruit flies, etc. All of them are decomposers or they would not be there.

I always have fruit flies flying out of my compost bin. If I cover the pile really well with grass or leaves they can't get to the fruit and other stuff and they seem to go away.