Bumble bees are clumsy fliers. They crash into things about once per second. But before scientists began filming them with high-speed videography, we didn’t know much about how they fly, nor about the obstacles they face.
“In the time you blink your eye, a bee beats its wings sixty-five times,” said biomechanical ecologist, Stacey Combes, who was an Associate Professor at Harvard University when much of this research was being conducted. (She now is an Assistant Professor at UC Davis.)
Bumble bees’ clumsiness stems not from poorly developed flying abilities, but from the variety of challenges they must deal with, particularly strong and unpredictable air flow, whilst trying to land on an unstable flower that also is buffeted by winds.
“[Bumble bees] are really very important pollinators of plants,” Professor Combes said. “So understanding how they fly, how they get around, what affects their flight, is really critical.”
To investigate this, she teamed up with her postdocs, Andrew Mountcastle and Nick Gravish, at Harvard University (both are now assistant professors at universities on opposite sides of the country). Together, they designed and constructed a system that allows them to capture a glimpse of how bumble bees navigate a cluttered space.
“These collisions are a fraction of a second. With high-speed cameras, we’re able to start to see what these collisions look like and how they affect the bumble bee,” Dr. Mountcastle said.
Most collisions involve the wings. But how can something as fragile as an insect wing collide with a solid object and not break?
Using high-speed videography, the research team discovered that bumble bees have joints near the middle of each wing. These joints are composed of the protein, resilin. It is this soft, elastic protein that provides flexibility to bumble bee wings, so they don’t break when the insect crashes into solid objects.
“In bee wings, we see something like five to nine resilin joints, particularly in the middle and back of the wing that allows them to bend along their length,” Professor Combes said.
“Think of it as the perfect rubber band.”
Resilin joints in bumble bee wings are an important evolutionary innovation for these insects, but they also provide important lessons to researchers who are designing and building lighter and more durable robots and drones.