The Flight Guidance Mechanisms of Honey Bee Swarms : 9
Figure 4. Flight speed versus flight angle for the bees in a flying swarm when it had flown 15 metres from its bivouac site. Bees with a flight angle of 0° were flying straight towards the new home; all the rest were flying at some angle to the left or right of the direction to the home site. The measurements of the flying bees are shown separately for the top and bottom layers of the swarm cloud. The units of flight speed are bee lengths per video frame
swarm flyovers ‘in the can’, the next step was to use point- tracking algorithms invented by engineers working on computer vision to make three- dimensional reconstructions of the individual bee’s flight movements within the flying swarm. The procedure involved examining each ellipsoidal blob (bee image) in a given video frame and then pairing it up with the blob on the next video frame that represented the same bee.
This process was repeated with the blobs of the second frame being paired with blobs of the third frame, and so on, to build up, frame by frame, detailed
trajectories of individual swarm bees as they flew across the video camera’s field of view. The size of each blob indicated the height of the bee above the camera, so the bees in the top and bottom portions of the swarm cloud were distinguished.
Streaking Confirmed The most important finding
revealed by this painstaking analysis of the video recordings is that the fast-flying bees were indeed streaking in the direction of the swarm’s flight, ie, toward the nest box. And, as is seen in Figure 4, which shows the individual bee’s flight speeds in relation to flight direction,
April 2015 Vol 97 No 4
www.bee-craft.com
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