Fancy Flying Makes For Better Honey?
To find out, Mandyam Srinivasan, an electrical engineer from the Queensland Brain Institute, The University of Queensland and the Australian Research Council’s Vision Centre, and colleagues first built a bee-landing platform that could be inclined at any angle from horizontal to inverted (like a ceiling), then they trained bees to land on it and began filming…
Having collected movies of the bees landing on surfaces ranging from 0deg. to 180deg., and every 10deg. inclination between, the researchers began the painstaking task of manually analysing the bees landing strategies, and saw that the bees” approach could be broken down into 3 phases.
Initially the bees approached from almost any direction and at any speed, however, as they got closer to the platforms, they slowed dramatically, almost hovering, until they were 16mm from the platform when they ground to a complete halt, hovering for anything ranging from 50ms to over 140ms.
When the surface was horizontal or inclined slightly, the bees’ hind legs were almost within touching distance of the surface, so it was simply a matter of the bee gently lowering itself and grabbing hold with its rear feet before lowering the rest of the body.
However, when the insects were landing on surfaces ranging from vertical to ”ceilings”, their antennae were closest to the surface during the hover phase.
The team saw that the antennae grazed the surface and this contact triggered the bees to reach up with the front legs, grasp hold of the surface and then slowly heave their middle and hind legs up too.
“We had not expected the antennae to play a role and the fact that there is a mechanical aspect of this is something that we hadn’t thought about,” Srinivasan said.
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Looking at the antennae’s positions, the team realised that in the final stages as the insects approached inverted surfaces, they held their antennae roughly perpendicular to the surface.
“The bee is able to estimate the slope of the surface to orient correctly the antennae, so it is using its visual system,” Srinivasan said.
But this is surprising, because the insects are almost completely stationary while hovering and unable to use image movement across the eye to estimate distances. Srinivasan suspected that the bees could be using stereovision over such a short distance, and is keen to test the idea.
Finally the team realised that bees are almost tailor made to land on surfaces inclined at angles of 60deg. to the horizontal.
“When bees are flying fast their bodies are horizontal, but when they are flying slowly or hovering their abdomen tilts down so that the tips of the legs and antennae lie in a plane that makes an angle of 60deg,” said Srinivasan: so the legs and antennae all touch down simultaneously on surfaces inclined at 60deg.
“It seems like they are adapted to land on surfaces tilted to 60deg. and we are keen to find out whether many flowers have this natural tilt,” Srinivasan said.
The bees” technique may help engineers design a new generation of automated aircraft that would be undetectable to radar or sonar systems and would make perfectly gentle landings, even in outer space.
The study has been reported in the Journal of Experimental Biology.