What can I do about it?

To get rid of your Fruit Fly problem you will need to follow a few simple steps:

1)  Keep any fruit that you have in the house in the refrigerator or covered containers.
2)  Keep all of the drains in the house covered or closed so the flies cannot use them as breeding sites. The
     flies will lay eggs in the black drain sludge.
3)  Build fruit fly traps and put them where the heaviest numbers of Fruit Flies are.  Once the traps have
     flies in them put them in the freezer or out in the cold (during winter) to kill them. 
4)  Wet mops and other cleaning items need to be dried out before being put away.

How do I build a trap?

To build a Fruit Fly trap you will need a bottle (ie beer bottle, glass or plastic jar), a piece of paper, some tape and rotting/fermenting fruit (banana or strawberry) or liquid (wine or fruity liqueur). Roll the paper into a funnel that will sit in the top of the bottle and tape it so it stays in the funnel shape.  Make sure that the opening at the tip of the funnel is less then 4mm wide.  Add the rotting fruit or liqueur to the bottle and then set the funnel on top of the bottle.  The tip of the funnel should not touch the fruit or liquid at the bottom of the bottle.  Run a piece of tape around the lip of the bottle so that it secures the paper funnel to the bottle.  Make sure there are no leaks where flies could escape once they are in the trap.  Now take the completed trap and place it where you have the greatest concentration of Fruit Flies. If there are lots of flies in the trap place it in the freezer for a few hours to kill the flies and then put back out to trap more flies.