SCV Outdoor Report: Watching Dragonflies
By Wendy Langhans
One morning early last week, I was sitting on the front porch slurping a cup of hot coffee. It was o'dark hundred, way too early for civilized folks to be up and about. With my eyes half open, I watched two dragonflies, darting back and forth, like runway models strutting and holding a pose. Their movements were unpredictably quick and precise. I wondered, "how do they manage to fly like that?
Dragonflies have two pairs of wings, one pair in front and one pair in back.
I assumed it must have something to do with their wings. When observing a dragonfly at rest, it's easy to see that dragonflies have two pairs of wings, a front pair and a back pair. But to truly be able to see these wings in motion, you need a high-speed video camera and the ability to observe their movements in slow motion. (For a slow-motion video of dragonfly flight from David Attenborough's "Life in the Undergrowth", click here.) When observed this way, scientists discovered these two pair of wings stroke in curves - more like a canoe paddle than a rowboat oar. And they don't always stroke in unison.
- Synchronized-stroking. The front and back pairs move in unison. This is used to maximize thrust and lift, especially when accelerating or quickly changing direction.
- Counter-stroking. The front and back pairs move 180 degrees out of phase. So while the front pair are moving down, the back pair are moving up. This stroke is very efficient when hovering, minimizing the amount of power needed to remain in a stationary position.
- Phase-stroking. The front and back pairs move 54-100 degrees out of phase. This is used for forward flight, providing a blend of efficiency and lift.
A four-wing design with independent-control and flexible stroke provides the dragonfly with the power needed for take-off and speed, plus maneuverability and efficiency.
About five hundred years ago, Leonardo da Vinci based his design of an "ornithopter", a wing-flapping flying machine, on his observation of birds. But I wonder - did he ever sit on his balcony watching dragonflies? What would his design have looked like if he had?
Upcoming Outdoor Events:
Saturday, October 3, at Placerita Canyon
October 3, 2009 (11:00 am - 12:00 pm)
An easy, 1-hour walk exploring the area's natural and cultural history.
October 3, 2009 (1:00 pm - 2:00 pm)
See, learn and ask questions about live native animals of the area.
Sunday, October 4, Ramona Days at Rancho Cumulos
October 4, 2009 (10:00 am - 4:00 pm)
A great place to take the family for a glimpse of Southern California history.
For more information, go to their website.
You can listen to stories like this every Friday morning at 7:10 a.m. on "The Hike Report", brought to you by your hometown radio station KHTS (AM1220) and by the Mountains Recreation and Conservation Authority.