"The unexpected thing I found was that as the bees fly faster and faster, they actually start to lower their huge hind legs below their body, instead of tucking them in to reduce drag like you would expect," she said. "It looks like the reason they're doing this is to create a nose-down pitching torque to help tilt their bodies forward to allow them to fly faster."
The technique is similar to how some old helicopters must tilt forward to offset wind drag before flying forward.
Combes, who is a research fellow in the Department of Integrative Biology at the University of California, Berkeley, also explained that when bees extend their legs, the limbs generate stabilizing forces, similar to how the extended arms of a spinning figure skater can improve stability.
Bees may reach a maximum flight speed of 23.8 feet per second, but at that speed, the insects can lose stability to the point where they may roll, fly upside down and even crash to the ground. At lower speeds, the legs can help to prevent such rolling and side-to-side movements.
Airplane Inspiration?
Combes said bee flying might inspire new miniature aircraft designs that incorporate a device that functions like bee legs, which are structured somewhat like airplane wings.
"The legs are slightly convex on the outer surface and concave on the inner surface, and have a row of hairs on the trailing edge (back)," Combes said.
"This is similar to the general design of an airfoil (airplane wing), where a convex upper surface and concave lower surface, as well as tapered trailing edge, helps the airfoil generate lift forces by causing air to flow more quickly over the top than the bottom."
Combes said that below a certain size, fixed wing or helicopter-type flying machines do not work, so engineers have to build a craft with flapping wings. The U.S. military and other groups hope to use such mini flying robots for search and rescue missions and other applications. Bees could inspire future designs.
"It may be helpful to be able to reduce the number of control components needed by using one structure, like the orchid bee legs, to control both pitch and roll," she explained.
Graham Taylor, a member of Oxford University's Animal Behavior Research Group, said he was surprised that stability limited the upper, rather than the lower, speed at which orchid bees can fly.
He explained that helicopters often experience problems when they attempt to hover slowly, but bees indicate fast flying creates more defined limitations.
While Taylor thinks it is possible that bees could inspire new miniature aircraft designs, he suggested to Discovery News that birds might make a better model.
He said, "The problem is that evolution works with whatever it has to hand, so while it makes sense for an orchid bee to evolve to use its legs for flight control, a large moveable tail surface — which insects have never evolved, but birds have — would probably be more effective for flight control."
