On August 28, 2017 I noticed what I thought was honey bees going in and out of the owl house. Got my camera and discovered it was paper wasps that had taken it over. After consulting with experienced bird house folks it was determined I would need to wait until a freeze killed or made the wasps go dormant to clean them out of the house and soap the sides and roof of the house so it does not happen again. By that time I figured I would have to wait another year to hope for owls, I would miss the best time for them to move in.
Common Paper Wasp (Polistes exclamans)