At a recent home inspection I came across an opening in the side of a home that was housing a bee hive. This video clearly shows why you should always make sure that openings in the exterior of your home are sealed. These bees get into the wall and displace the insulation as they build their colonies. My recommendation to the new home owner was to have these bees exterminated, removed, and then to have the insulation replaced... Oh, and to make sure that all openings in the home's exterior are sealed.