The fast and formidable dragonfly.
Illustrations by Robert Meganck
One bright summer day, as you stroll near a lake or a pond, a flash of green hanging in midair catches your eye: a dragonfly, one of the coolest insects around. Maybe it’s their festive colors, from iridescent green and blue to crazy orange, or their elegantly etched wings. Maybe it’s the weird wrap-around, composite eyes, which have up to 28,000 facets, giving this darting predator the look of some kind of alien biker aviator.
Could this one be a Rusty Snaketail or a Halloween Pennant? A Cherry-faced Meadowhawk or a Chalk-fronted Corporal? You want a better look and begin to ease closer, glancing down for a split second, then back up—and it’s gone. Really gone, nowhere to be seen, poof, gone, that fast.
Other bugs can hover, and other bugs are speedy, but none are quite as agile as the dragonfly, order Odonata, which also includes the smaller, daintier damselfly. Able to reach speeds up to 50 km/hour, dragonflies can also fly backwards, tack left and right and up and down, and even glide (whereas other insects just drop when they stop flapping). They’re also somehow able to triangulate the location of where that tasty mosquito or midge is going to be and then zip over and intercept the victim.
That’s one interesting detail uncovered in research performed at Janelia Farm Research Campus, in Ashburn. There, Anthony Leonardo and Robert Olberg are examining the neurological basis of exactly what makes the dragonfly such a formidable predator. Leonardo describes two classes of dragonfly for the HHMI Bulletin: hawkers and perchers. (Fun fact: The fossil record shows that dragonflies were in fact as big as hawks at one time.) Hawkers, Leonardo says, are “constantly flying through the air, and they’re eating while they’re flying, catching [insects] and stuffing them in their mouths.” Perchers, on the other hand, are a little more predictable, and thus easier to study: They perch, they see a prey item, they fly up and catch it and return to the perch. “That takes a quarter of a second or a second, the whole thing, so they fly very fast.” Leonardo and his team are developing a microtelemetry device that will be inserted into dragonflies’ neurons (micro indeed!). What they learn, says Olberg, may have relevance for robotics and other technologies that mimic biological mechanisms.
Actually, compared to many insects, some dragonfly species are fairly large, which helps scientists aiming to study them using attached transmitters. Researchers at Princeton University used such technology to analyze the journey of the Green Darner, one of nine migratory dragonflies native to North America. The results revealed striking similarities between the flyways of dragonflies and migratory songbirds. Not only did they follow the same path, but they also built up fat reserves in advance and were able to reorient themselves after mistakes—like birds. It’s still unknown whether either navigates by terrain, sunspots or magnetic fields.
One thing for sure, though: It’s the southbound group’s offspring that flies north in spring, because the parents can’t possibly live long enough to make the return trip. The life cycle of the dragonfly isn’t exactly short, but the bulk of it is spent in a water-bound nymph phase that can last up to four years; the adult phase is no longer than a few weeks. And yes, when you see a pair of dragonflies flying in tandem, they’re doing what you think they’re doing: making new little nymphs. Think of it as an entomological mile-high club.
The female will lay her eggs in a pond, either directly into the water or injected into a plant stem, depending on her species. So, of course, wetlands are the best place to find dragonflies—and the health of dragonfly populations depends on the health of wetlands. Thanks perhaps to its diversity of wetland habitat, Virginia ranks second in the nation in terms of dragonfly diversity, according to a report produced by the Virginia Natural Heritage Program, so there’s ample opportunity to see them here. A hint, though: With their near-360-degree visual field, they’ll see you coming unless you’re in their very tiny blind spot. You want a closer look at that Cinnamon Shadowdragon or that Duckweed Firetail? Get behind it.