The cooler weather and lack of forage means that all the Hymenopterans are getting a bit desperate for forage. As a result, the hive has started attracting lots of unwanted attention from yellow jackets. However, my girls are more than up to the task of defending the hive. They guard it with such ferocious vigilance that I almost feel bad for would-be intruders because they haven't got a chance.
Here is a short video I took. A yellow jacket tries sneaking into the hive, but guard bees quickly take it out.