DAINTY, YET DEADLY
African lions roar and strut and act the apex carnivore, but they're lucky to catch 25 percent of the prey they pursue. Great white sharks have 300 slashing teeth and that ominous soundtrack, and still nearly half their hunts fail.
Dragonflies, by contrast, look dainty, glittery and fun, like a bubble bath or costume jewelry, and they're often grouped with butterflies and ladybugs on the very short list of Insects People Like. Yet they are also voracious aerial predators, and new research suggests they may well be the most brutally effective hunters in the animal kingdom.
When setting off to feed on other flying insects, dragonflies manage to snatch their targets in midair more than 95 percent of the time, often wolfishly consuming the fresh meat on the spur without bothering to alight.
"They'll tear up the prey and mash it into a glob, munch, munch, munch," said Michael L. May, an emeritus professor of entomology at Rutgers. "It almost looks like a wad of snuff in the mouth before they swallow it."
Next step: grab more food. Dragonflies may be bantam, but their appetite is bottomless. Stacey Combes, who studies the biomechanics of dragonfly flight at Harvard, once watched a laboratory dragonfly eat 30 flies in a row. "It would have happily kept eating," she said, "if there had been more food available."
In a string of recent papers, scientists have pinpointed key features of the dragonfly's brain, eyes and wings that allow it to hunt so unerringly. One research team has determined that the nervous system of a dragonfly displays an almost human capacity for selective attention, able to focus on a single prey as it flies amid a cloud of similarly fluttering insects, just as a guest at a party can attend to a friend's words while ignoring the background chatter.
Other researchers have identified a kind of master circuit of 16 neurons that connect the dragonfly's brain to its flight motor center in the thorax. With the aid of that neuronal package, a dragonfly can track a moving target, calculate a trajectory to intercept that target and subtly adjust its path as needed.
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