ZIPLOCK FLY BARRIERS

IS IT A MYTH THAT FILLING A QUART SIZE ZIPLOCK BAG AND HUNG ABOVE HEAD LEVEL OUTSIDE YOUR DOOR WILL STOP FLY'S FROM COMING IN ??
(THE STORY GOES THAT THE REFLECTION FROM THE LIGHT AND WATER SCARES THEM,OR EVEN THAT THEY SEE THEMSELVES AND FLY AWAY ??