Neither bees nor wasps will swarm if far from their nests mainly because there won't be many as they forage in a solitary manner. But when hornets attack as a

Neither bees nor wasps will swarm if far from their nests mainly because there won't be many as they forage in a solitary manner. But when hornets attack as a group, then they swarm, and they use their pheromones to aid in swarming. See: https://www.youtube.com/watch?v=onq9ixC7OEg https://www.youtube.com/watch?v=onq9ixC7OEg https://www.youtube.com/watch?v=D00mEROqKwU https://www.youtube.com/watch?v=D00mEROqKwU https://www.youtube.com/watch?v=vx2EA_ooCf0 https://www.youtube.com/watch?v=vx2EA_ooCf0 where beekeepers use sticky sheets to get one hornet and then all the other hornets will join the one because they are all attracted to its aid by its pheromones.