Stewart Robert Hinsley writes
In message , Wally
writes
I have a plastic compost bin, like an upside down
dustbin, all working very well but just recently when
I remove the lid to add something to the contents, I
am attacked by a million small flies.
Should I do something to get rid of these or are they
doing any good in there ??
If they are working on the compost like the worms do
I can put up with them but if they are doing no good
then they will have to go.

Probably sciarid flies (fungus gnats, fungus midges). They can be a
problem in seed trays, but I don't know of any reason that they would
be a problem in a compost bin.

Or possibly fruit flies?
They'll get bored and go elsewhere when there are no more rotting fruit
smells to attract them.


--
Kay