Is it true that bumblebees shouldn’t be able to fly? asks a reader.
No one’s sure where the myth started, but it has legs (er, wings): Bumblebee flight is impossible. According to the principles of aerodynamics, the story went, a big, fuzzy bumblebee, powered only by tiny wings, shouldn’t leave the ground. A French book from the 1930s, for example, cited calculations that “proved” insects in general shouldn’t be able to fly. But using mechanically-driven fixed aircraft wings to model the flight of bumblebees and other insects just didn’t work.
The mysteries of insect flight are still being unraveled, but today’s scientists say insects fly “in a sea of vortices,” using the swirling eddies of air created by their beating wings to stay aloft.
Bumblebees beat their wings up to 200 times a second, faster than the nerve impulses to their muscles can fire. This works because bumblebee wing muscles don’t contract and expand with each electrical signal. Instead, they continuously vibrate, like a repeatedly plucked guitar string.
When a bumblebee rests, its body temperature drops (or rises) to that of its surroundings. But according to entomologists, the temperature of a bumblebee’s wing muscles must be a toasty 86 degrees F. to lift the bee into the air. So to fly to the nearest flower cafeteria, a bumblebee must dramatically raise its temperature in all but the hottest weather.
How? Basking in the sun isn’t usually enough, so the bee will shiver her way to a higher temperature. By rhythmically contracting and releasing her abdominal muscles (faster and faster as her temperature rises), a bee generates enough warmth to take flight. The warmer the air temperature, the quicker the lift-off. On a chilly, 42-degree day, a bumblebee must pump her thorax muscles for a tiring 15 minutes to reach 86 F.
Once in flight, a bumblebee’s muscle temperature remains in a range of about 86 to 111 F. All of this activity expends enormous amounts of energy, provided by the sugars in flower nectar. Not surprisingly, scientists have found that bumblebees are especially attracted to warm flowers, floral rooms whose color and shape keeps them heated in the sun.
According to Oxford University research published this month, bumblebee flight really is different from that of dragonflies and other insects. Using a smoke-filled wind tunnel and cameras snapping 2,000 images a second, researchers found that bumblebee flight is surprisingly inefficient. For example, a bumblebee’s left and right wings flap independently of each other. And instead of using the varying air pressure at its wingtips to provide some lift, bumblebees use “brute force” to fly and hover. Bumblebees, say scientists, are the “tanker trucks” of the flying insect world, using incredible amounts of energy to lumber (charmingly) through the sky.
In fact, bumblebees manage to fly even in places where human beings find it difficult to breathe. On Earth’s highest peak, Mount Everest, bumblebees have been sighted at more than 18,000 feet up. Although there’s much less air pressure for tiny wings to beat against, bumblebees power on, hot to the touch even in the frigid cold.