Natalie Angier has a lovely new post about dragonflies in today’s New York Times: “Nature’s drone: pretty and deadly.” As usual, it’s a felicitious combination of good writing and intriguing science, and there’s a nice video on dragonfly research to accompany it, as well as a new feature: a movie that heads the story and starts automatically. These lovely insects turn out to be the honey badgers of the insect world, mean and voracious predators. A few bits from the article:
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.”
. . . as a dragonfly closes in on a meal, it maintains an image of the moving prey on the same spot, the same compass point of its visual field. “The image of the prey is getting bigger, but if it’s always on the same spot of the retina, the dragonfly will intercept its target,” said Paloma T. Gonzalez-Bellido, an author of the new report who now works at the Marine Biological Laboratory in Woods Hole, Mass.
As a rule, the hunted remains clueless until it’s all over. “Before I got into this work, I’d assumed it was an active chase, like a lion going after an impala,” Dr. Combes said. “But it’s more like ambush predation. The dragonfly comes from behind and below, and the prey doesn’t know what’s coming.”
She also describes the results given in a new paper in Current Biology (I haven’t read it): by monitoring single neurons, researchers have found that dragonflies have a form “selective attention” (paying full attention to two objects alternately) that’s usually found in species with much more complex brains. This is apparently useful in helping dragonflies select a single prey item from a moving swarm.
Here are two dragonfly videos. First, an Attenborough clip showing their four wings working in slow motion:
. . . and an 8.5-minute video on the general biology of dragonflies (order Odonata) and mantids (order Mantodea).