The period of September sees the crabro wasp hunt in front of the entrances of the hives, the small bees to defend themselves, gather in front of the entrance, in this way they are able to receive the tired bees that return, without leaving them at the mercy of the hornets.
thanks to this system, if the hornet wants to get too close, the bees are able to capture and suffocate it with the "hot ball" technique.
The pressure of the hornets, in front of the hives is constant, in a day more than 200 hornets go back and forth, to hunt the small bees.
an old photo, to understand what we are talking about