Scientists have discovered the reason behind the phenomenon of "shimmering" in giant honeybees: it's a defense mechanism against predatory hornets!
In the PLoS ONE study, Gerald Kastberger and colleagues focused on the shimmering behavior in giant honeybees, the intriguing, docile, nest-based trait reminiscent of the Mexican waves seen in football stadiums. It was previously known that shimmering was evoked by visual stimuli of predators—particularly hovering wasps. This highly coordinated response aligns hundreds of colony members and displays a remarkable capacity of fast communication within a society, unique in the animal kingdom.
When a giant honeybee colony shimmers, it has two potential addressees: firstly, its nest mates, which coordinate themselves to participate in the shimmering, and which possibly become aroused or alarmed. The authors posit that the members of the group, which are assembled in the dense networks of a "bee curtain" on both sides of the comb, continuously produce and receive information about the state of the colony, reflecting its day-to-day business of foraging, reproduction, reorganization and defensive actions (such as shimmering). Secondly, the potential predators such as wasps and mammals are targeted—these are thought to be influenced by the dynamic visual cues of shimmering.
http://en.wikipedia.org/wiki/Audience_wave