swarm

The term swarm (shoalingswarming or flocking) is applied to fishinsectsbirds and microorganisms, such as bacteria, and describes a behavior of an aggregation (school) of animalsof similar size and body orientation, generally cruising in the same direction. Group size is a major aspect of the social environment of participants.

Swarming of honey bees is a more specific term, referring to the reproductive action of an entire colony of bees (as opposed to the reproduction of single bees); see Queen bee and Honey bee life cycle.

http://en.wikipedia.org/wiki/Swarm