We applied simulated pollen or nectar loads of equal mass to Bombus impatiens bumblebees and examined flight performance in a wind tunnel under three conditions: flight in unsteady flow, tracking an oscillating flower in smooth flow, and flower tracking in unsteady flow.
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When weighed down by pollen, bumblebees gain stability in the face of hard wind conditions.
When bees collect nectar, they stick it to their abdomens. The study is published online today in the Proceedings of the National Academy of Sciences. Ravi and his team of colleagues wanted to see how the different cargo positions affected the flight patterns of the bees, so they devised a plan to figure it out. On some, they attached the weights to their legs, in place of pollen, while others had weights glued to their torsos, to simulate loads of nectar.
New bee experiments are focusing on whether the weather conditions influence whether bees choose to gather pollen or nectar.
By contrast, when an insect was carrying nectar, the researchers thought it would have added manoeuvrability because its weight was focused near its centre of gravity.
Most bumblebees spend a good chunk of their lives foraging for enough food to feed the queen, flying heavy loads of either pollen or nectar to and from the hive.
Bee flight performance was measured by gluing tiny ball bearings to the bees, either to their legs or abdomens, and sent them buzzing down a wind tunnel with a fake “flower” at the end of it. The bees’ were filmed with a high-speed camera. The wind conditions were varied and the bees’ flying was also tracked in the presence of a moving robotic flower, to determine just how maneuverable and accurate the bees can be inflight.
“Such a test has never been done”, he says. “It shows there’s a trade off between stability and maneuverability”. With the latter stored down around the legs, the bees did not have the same level of maneuverability in flight, but they were “more stable”, NPR reported.
Researchers like Ravi and Mountcastle predict that they do, perhaps choosing to take advantage of pollen’s more stable loads on windier days, and carrying the easily-maneuvered nectar on calmer ones.
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