Friday, August 07, 2009

Wing-whirring

At the FT, Ángel Gurría-Quintana on a dragonfly safari (FT site registration required):
Our dragonfly safari is coming to an unsatisfactory end when a flying critter buzzes out of the reeds and into sight, before flying away and back again. It’s the biggest dragonfly I’ve ever seen – perhaps the length of my hand-span. It hovers tantalisingly close, suspended in mid-air, then shoots vertically up into the trees, flies around them and returns. It darts at me, stops a few inches from my face, and then reverses. It seems to be examining me, taunting me. If this were a larger animal, I’d feel very threatened.

“A Southern Hawker,” Curry says, a note of excitement in his voice, “and it’s showing classic behaviour.” The British Dragonfly Society’s webpage describes the Southern Hawker as an “inquisitive” species, most often seen individually, which “may fly quite close to investigate observers”. This extraordinary display goes on for a few minutes, until – contrary to our expectations – it lands on some nearby reeds. “It’s posing for us,” says Curry.

We are now able to appreciate its characteristic paired yellow spots. It is a male, as is apparent from its slightly constricted abdomen and the claspers on the tip of its tail, which it uses to attach itself to females. We approach cautiously. Its wings shudder, shimmering in the weak sunlight. “That’s called wing-whirring,” says Curry. “It’s warming up its wing muscles in case it needs to take off suddenly.”

I am fascinated by the dragonflies’ flight control mechanisms. They have eight abdominal muscles, Curry explains, which they use to move each of their four wings independently. They can fly in ways that are inconceivable for any other animal. Southern Hawkers can fly for as long as an hour without resting. Ours gives a final whirr, and shoots off.
Also worth noting: Ludovic Hunter-Tilney on the vinyl countdown; lunch with Jared Diamond.

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