Flies are drawn to piles that are both too green and too wet. It is perfect breeding grounds for them. And kitchen foods wastes are almost exclusively greens and wet.

My suggestion would to add a substantial amount of dry browns to the bin - straw, brown leaves, papers, paper grocery sacks, cardboard, etc. - whatever you can get. I think you will find a substantial reduction in the number of flies.

The composting FAQ here has many great tips and lists of useful components. Just click on the FAQ button at the top of the forum page. Good luck. ;)

Dave

I add a layer of leaves to the top of mine. Helps keep the moisture in too.

Thanks for the comments.

I added a bin bag of shredded office paper about 9 days ago. The flies reduced and have now increased again.

I can try shredded newspaper if you think it would help.

Jamie

I prefer leaves to plain paper, but if you don't have any available, shredded newspaper is fine. Mix some in with the pile to dry it a little and balance your surfeit of greens, then put a layer on top. Next time you add some greens, mix them in with this layer, and then add another layer of plain paper, etc. This will keep too many flies from getting at your fresh greens.

In a closed container the moisture that is in the material you put in has no means of escape so it stays, there simply is not enough air exchange. The presence of all of the insects you describe indicates your mixture is too wet, none of those can exist except where there is lots of moisture. You need to increase the amount of dry material but in to absorb that excess moisture, shredded paper is good if nothing else is available,