Fruit fly thingies

If they are fruit flies put some wine in a glass and cover it with cling film that has been pierced with tiny holes. They die happy...

They sound like the fungus flies that feed on decaying leaves and so on in plant pots - they are small and flittery. Putting the pot outside in the wind, cold and wet for a while gets rid of some of them, but they are likely to increase again. Maybe a pest-killing spray would see them off, or repotting the plants, having got rid of all the compost and dead material around the roots and washed the pots well.