What Makes Dragonflies So Extraordinary
Before bats, before birds, before pterosaurs, a dragonfly-like insect was probably the first thing to fly on Earth.
JESSICA WARE (Division Chair of Invertebrate Zoology, American Museum of Natural History): Before birds, before bats, before pterosaurs, the first thing we think to fly was something that was like a dragonfly.
The extinct genus Meganeura, an ancient relative of today's dragonflies, was just a little smaller than a crow, making it one of the largest insects ever known. It buzzed around 350 million years ago, even before dinosaurs walked the earth.
So since then, dragonflies have evolved lots of different styles of flight. Today, they’re some of the strongest flyers in the insect world, speeding up to 30 miles per hour, hunting prey like mosquitoes and flies, and even hovering effortlessly.—a rare skill. It makes us as researchers want to ask, how are dragonflies so darn good at flying?
DIRECTOR: Hey, Jessica, what's your favorite insect?
WARE: So hands down, always has been, always will be, forever until the end of time—Odonota, which are dragonflies and damselflies. And in particular, dragonflies are my jam. Never, ever get tired of them, from when I was a little kid. Many, many times laying on the dock next to Lake Muskoka in Canada, a horse fly would come along and a dragonfly would come and snatch it up. And I thought, “That's boss. Thank you for doing- Thank you for doing that.”
So, I appreciated them for their hunting prowess and just- they're just beautiful insects. But then once I went to graduate school and I learned more about them, I realized that their evolutionary history is so long. Right? And they have these unique adaptations. And so I just learned that the more I learned about dragonflies, the more there was to learn.
DIRECTOR: Are dragonflies good hunters?
WARE: I would say dragonflies are among the best hunters. There’s few other insect predators that are as good at catching things as dragonflies. Dragonflies will really eat anything, including each other, but importantly, they eat flies and mosquitoes that we humans don't like. The mosquitoes that vector or spread malaria, dengue and yellow fever? Dragonflies eat them. And their success rate at hunting is often close to 100%.
They do intercept style predation. So instead of flying to where their prey is right now, they fly to where their prey will be and they kind of cut it off at the pass. And so they need to be able to change course dramatically.
They can do a lot of this style of flight because they have direct flight muscles where the wings kind of attach directly to the muscles inside their thorax—because basically their whole thorax is flight muscle—and they can move each wing independently. That allows them to kind of have this power and maneuverability in the way that other other insects don't have.
DIRECTOR: When you say powerful, what are we talking about?
WARE: Well, I mean, so dragonflies are fast. There's some dragonflies that can fly up to 30 miles an hour.
DIRECTOR: And just to be clear, that's faster than Usain Bolt.
DIRECTOR: But go on.
WARE: Some dragonflies are able to fly really long distances. So people talk about monarchs. They talk about whale movement. There's a lot of animals that that travel long distances. But a single individual of a wandering glider or Pantala flavescens can travel thousands of kilometers in its lifetime.
Dragonflies are able to do kind of remarkable twists and turns, maneuverability, changing their height in the air column very quickly, turning on a dime, in some cases, in part because of their wing venation. Wing venation just means the arrangement of veins in an insect’s wing.
DIRECTOR: Yeah. Those veins on their wings are so striking. Do they serve a special purpose?
WARE: Absolutely. So the wing vein patterns in dragonfly wings are directly correlated with flight style. We generally group dragonflies into two styles—fliers and perchers. And then there's some intermediates that we don't really know where they fit, if they're a percher or a flyer.
DIRECTOR: So fliers, I take it they're good at flying?
WARE: For a majority of the day, they are on the wing hunting. They're on the wing finding a mate. They're on the wing evading predators that are kind of trying to hunt them. So they have a very dense amount of wing veins, and that makes the wing much stiffer. We think that increased surface area might decrease energy expenditure when they're doing this kind of gliding style flight.
DIRECTOR: And perchers?
WARE: They will fly around to find a mate, they fly around to find food. They might be territorial, so they will fly around to chase other males out of their territory, but then they'll return to a perch.
They're flying in and amongst tree branches. They’re flying in- around rock. Every time dragonfly wings hit any of those things, it actually can tear them because dragonfly wings are rather fragile. So they need to be able to kind of maneuver around those obstacles, so their wings have fewer veins and are much more bendy and flexible.
But back to how dragonflies got to be such good fliers... We might think it's important to understand whether perches or fliers came first. But it turns out the origins of different flying styles and flight itself are much more complicated than that. So in the past, like in maybe 100 years ago, people kind of sorted dragonflies into these different piles. And one of the things that they looked at was wing venation, because it's so easy, you can just look at the wings.
But when we used DNA to analyze dragonflies and built our first molecular family trees, they didn't agree with what sorting by the wing vein patterns had told us. So, how do we figure out how flight developed? We need to untangle dragonfly evolution. My grad student, Rhema Uche-Dike, is one of the people working on that puzzle.
RHEMA UCHE-DIKE (Ph.D. Student, City University of New York): I study dragonfly phylogenetics and that's essentially looking at dragonflies from a family tree perspective—looking at how Species A is related to Species B and how Species B is related to Species C. I'm looking at this particular family called Macromiidae and-
WARE: The river cruisers.
UCHE-DIKE: The river cruisers. They have these unique flight patterns where they fly right in the middle of rivers and what is really interesting and funny and good for me at the same time is since I can't go in the middle of rivers, they happen to also fly down the middle of roads because they somehow think roads are rivers. And that's good for me because I can catch them on the roads.
WARE: Macromiidae, like Rhema studies, and dragonflies from a totally different family, Aeshnidae, are a great example of how two distantly related groups can share the same wing types and flight styles. They both have classic flyer wing shapes that allow them to fly long distances at fast speeds, spending very little time on the ground.
Just looking at the flight styles, we might have thought they were close cousins, but now the trees, these phylogenies that we're building with DNA, are painting a much more complex picture. And to fill out those trees, we need to be able to sequence the DNA of many, many dragonfly species.
UCHE-DIKE: If you study evolution, you're trying to look at little changes that have happened over a long period of time. So you need to get enough data to be able to quantify how much change is is really happening. So collecting out today helps us, you know, boost data and knowledge and the number of dragonflies there are.
If you're looking for the origin of flight, you want to trace it back to as far back as you can go. And-
WARE: Like, the answer is always that you need a tree, right?
To ask questions about the origin of flight—how often did perching style flight evolve? how often did flying style flight evolve? certain wing vein patterns? did they arise multiple times because of flight behavior or because of ancestry?—we can't really answer any of those questions without having a tree, without having a phylogeny.
And then we can look to see whether or not there's a certain group maybe that share a common ancestor that have a certain particular trait, or if instead these traits are actually not related in any way to their evolutionary history. When we see that it's a clue, it tells us this is independent of phylogeny. There's something else that's causing convergence.
If two individuals that have very, very distant relatives, if they both have this correlated wing vein pattern, that's interesting! That makes us want to ask why. What are some of the drivers that would lead them to both do this kind of cruising style flight or gliding style flight? Is it predators? Is it their habitat?
So it's interesting that you say that that Macromiidae as a family might be- How old did you say that it was?
UCHE-DIKE: About 20- 15 to 20 million years ago.
WARE: So that's after kind of what we think is the rise of modern birds. As the skies started to fill up with birds, with bats, with pterosaurs, we start seeing the evolution of more particular styles of flight maneuverability, speed.
So flight styles may have developed not because Species A was a close cousin of species B, but because they both face the same kind of selection pressure, like a response to threat or taking advantage of a similar opportunity.
What gets you kind of jazzed about studying dragonflies? What makes you want to study them?
UCHE-DIKE: I think of studying dragonflies as a win-win because in science, at least in biological sciences, I think you're either interested in an organism or you're interested in a concept. And for studying dragonflies, I'm interested in both. And dragonflies are really old insects. So that helps with, you know, studying both the organism and both the concepts of phylogenetics.
WARE: I think that understanding the evolutionary trajectory of species on the planet is vital. I think when I was first trying to decide what type of entomology I wanted to do, kind of I wanted to be an entomologist, I thought that maybe I should do something with food security or crop management, something that would be for the greater good.
WARE: But then once I learned about evolution and systematics, I kind of realized that that actually is for the greater good, like understanding the origin of life, 400 million years of evolution, of flight, of reproductive behavior, I mean, actually helps us understand and conserve biodiversity.
UCHE-DIKE: Yeah, that's very exciting, because when you know what happened in the past, you're able to sort of predict what happens in the future, you know.
WARE: So, you never wake up thinking, “Man, I wish I was studying beetles today”? I never do.
UCHE-DIKE: Nah, I never do.
WARE: Humans have used dragonfly wing venation patterns for artwork and for beauty.
We know that there's lots of lore like my grandmother used to say if you fell asleep by the water, a darner would sew your lips shut because the ovipositor, or egg-laying apparatus, looks sort of like a darning needle. That's of course, not true.
And then there are other cultures that really have revered dragonflies. Many of the military garb that was worn in ancient Japan actually had dragonflies because they were considered to be very powerful.
Do you know any dragonfly lore? Tell us about it in the comments.