Overcrowding and congestion in the nest are factors which predispose colonies to swarm. The presence of an old queen and a mild winter also contribute to the development of the swarming impulse. The tendency to swarm is usually greatest when bees increase their population rapidly in late spring and early summer. In Nebraska, this would be in May and June. No - honey bees exhibit defensive behavior only in the vicinity of their nest.
Defensive behavior is needed to protect their young and food supply.
A honey bee swarm has neither young nor food stores and will not exhibit defensive behavior unless unduly provoked. When honey bees swarm they will settle on a tree limb, bush, or other convenient site. The cohesiveness of the swarm is due to their attraction to a pheromone produced by the queen. The swarm will send out scout bees to seek a cavity to nest in and will move on when a suitable nesting site is found. Rarely, swarms may initiate comb construction in the open if a suitable cavity cannot be found.