The mechanism of flight guidance in honeybee swarms: subtle guides or streaker bees?

When a honeybee swarm takes off to fly to its new home site, less than 5% of the bees in the swarm have visited the site and thereby know in what direction the swarm must fly. How does the small minority of informed bees indicate the swarm's flight direction to the large majority of uninformed bees? Previous simulation studies have suggested two possible mechanisms of visual flight guidance: the informed bees guide by flying in the preferred direction but without an elevated speed (subtle guide hypothesis) or they guide by flying in the preferred direction and with an elevated speed (streaker bee hypothesis). We tested these hypotheses by performing a video analysis that enabled us to measure the flight directions and flight speeds of individual bees in a flying swarm. The distributions of flight speed as a function of flight direction have conspicuous peaks for bees flying toward the swarm's new home, especially for bees in the top of the swarm. This is strong support for the streaker bee hypothesis.