Aug 18, 2012

Dragonflies: The Flying Aces of the Insect World


Miles O’Brien: This dragonfly is grabbing the meal on the go.

Stacey Combes: This attempt is so fast that unless we film it in high-speed we can’t see whether it caught the prey. But when it gets back to its perch, if we see it chewing we know that it was successful.

Miles O’Brien: With support from the National Science Fundation, Harvard university biomechanist Stacey Combes, wants to understand how dragonflies pull off these complicated aerial feats; hunting, and even reproducing in midair. She and her team set up their lab near a pond outside Boston, right in the heart of dragonfly country.

Student: All right, I got one. I lost it.

Miles O’Brien: Clearly it's not easy to catch a dragonfly.

Student: I got one.

Miles O’Brien: Check out this frog. In this specially built netted enclosure, Combes’ team set up eight high-speed cameras. Then they release a dragonfly and some tasty fruit fly prey to watch what happens next.

Stacey Combes: They’ll go up in midair, catch the prey with their hands, or with their feet turn upside down and glide back to stick. And the whole capture will take maybe a second, or a second and a half. This one’s missing about half of its left front wing and yet it still does an amazing job catching the fruit fly in midair.

Student: It only takes about half a second for this to happen.

Stacey Combes: They caught, you know, about 90 or 95 percent of the prey that we gave them. And interestingly, they’re one of the most ancient groups of insects. They’ve had a long time to evolve their skills as predators.

Miles O’Brien: About 300 million years. These four-winged insects predate dinosaurs. They can fly straight up, straight down, hover like helicopters, and disappear in a blur. And their eyesight?

Amber DesLauriers: Almost its whole head is eye.They can see pretty much all the way around their head, except right behind them.

Miles O’Brien: Dragonflies mate and lay eggs in flight.

Stacy Combes: Do you see her like just dipping in the water?

Student: She’s trying to lay eggs; the male’s trying to mate with her.

Miles O’Brien: Combes says engineers are looking to the dragonfly for inspiration in small scale aircraft design.

Stacy Combes: There's a lot of interest in building, you know, robotic, smaller robotic devices.

Miles O’Brien: And she says better understanding of dragonflies could lead to more effective mosquito control strategies.

Stacy Combes: They may consume 30 mosquitoes a day. They could even consume hundreds a day.

Miles O’Brien: And that’s an idea that could really take flight.

Miles O’Brien: For Science Nation, I’m Miles O’Brien.

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