Dragonflies and Damselflies: A Life's Journey from Water to the Sky

When we see a dragonfly, we normally see adults, which are capable of impressive aerobatics and have astonishing eyesight. Yet these fearsome aerial predators began life underwater, and when they undergo the transformation from nymph to adult they also change from water to air. Dragonflies truly are amazing! 

Joining us to talk about these incredible animals is Dr. Jessica Ware from the American Museum of Natural History in New York, where she is an Associate Curator and the current Division Chair in the Division of Invertebrate Zoology. Jessica’s research focuses on the evolution of behavioral and physiological adaptations in insects, with an emphasis on how these occur in dragonflies and their close relatives, damselflies. Her research group uses genetics to study the evolutionary relationships between species and uses these tools to inform their work on reproductive, social, and flight behaviors in insects.

Thank you for listening! For more information go to xerces.org/bugbanter.

Transcript

Rachel: Welcome to Bug Banter with the Xerces Society where we explore the world of invertebrates and discover how to help these extraordinary animals. If you want to support our work go to xerces.org/give.

Matthew: Hi! I'm Matthew Shepherd in Portland, Oregon.

Rachel: And I'm Rachel Dunham in Missoula, Montana.

Matthew: When we see a dragonfly, we’re normally seeing adults, which are capable of impressive aerobatics and have astonishing eyesight. Yet these fearsome aerial predators began life underwater, and when they undergo the transformation from nymph to adult they also change from water to air. Dragonflies truly are amazing!

Matthew: Joining us today to talk about these incredible animals is Dr. Jessica Ware from the American Museum of Natural History in New York, where she is an associate curator and the current division chair in the division of invertebrate zoology. Jessica’s research focuses on the evolution of behavioral and physiological adaptations in insects, with an emphasis on how these occur in dragonflies and their close relatives, damselflies. Her research group uses genetics to study the evolutionary relationships between species and uses these tools to inform their work on reproductive, social, and flight behaviors.

Matthew: Thank you for joining us today.

Jessica: Thanks for having me.

Rachel: Yeah, we're super excited to talk about dragonflies. So to start us off, we've talked about a lot of different types of insects on this podcast—can you tell us how dragonflies are unique among that group of animals?

Jessica: Well, I mean dragonflies and damselflies—we often use the word dragonflies to mean both, just as an aside. They're in the order Odonata and that is probably the earliest branching lineage within the winged insects or the Pterygota. Sometimes we recover mayflies and dragonflies, a sister to the rest of the winged insects. Sometimes we recover dragonflies assisted to the rest. Or mayflies. So regardless, they probably were among the first things to take to the skies.

Jessica: So they're unique in a lot of ways. They do some things that are different from the rest of the insects. So both mayflies and dragonflies, they have the—they don't have the same basal sclerites at the base of their wings that Neoptera have—things like mantises or beetles. So they can't fold their wings perfectly over their back. They kind of have their wings either sticking out to the side for dragonflies, or kind of sticking outwards in the back part for damselflies. They can't neatly fold their wings because they don't have those sclerites that the Neoptera, or the rest of the winged insects, have.

Jessica: Dragonflies also have something different in the way that they have two types of muscles. There's indirect flight muscles and direct flight muscles. And for dragonflies, they have a kind that nothing else has, which causes like the deformation of the thorax, with the muscles directly attached to it. 

Jessica: They also have indirect sperm transfer. They have two penises. They have a penis at the tip of their abdomen, and a penis at the base of their abdomen. They put the sperm into the base of their secondary genitalia. And that's through which, you know, is transferred to the females. But they also use that secondary genitalia for sperm displacement to scrape out the previous male sperm, because females can store sperm and males presumably wanna ensure paternity.

Jessica: So that's also kind of unique, I would say. They're really—they do interception-style predation, which isn't unheard of in other groups. But there are other groups like mantises that are very visual predators, just like dragonflies. But dragonflies, as highly mobile flying predators, they're able to kind of cut their prey off at the pass, kind of like what a lion would do. 

Jessica: Color is a really big part of the story. Some of them migratory and travel really long distances. Some of them don’t. Some of them they stay in the pond from which they, you know, emerged as a nymph. They have a really good fossil record, because wing venation makes excellent compression fossils. And they're near water, which is kind of another ingredient that you need to have a good compression fossil. 

Jessica: So we know an awful lot about the evolutionary history of dragonflies because of this fossil record and because, I think, they're charismatic. So over the history of entomology, a lot of people have been like, you know, excited about dragonflies. So we have studies about their morphology. More recently, we have a lot of genomic and genetic information about them. And all of this you can kind of knit together into an understanding. Our goal is to really try and know everything we can about the 6,400 to 6,500 species, which is really hard to do that for beetles.

Rachel: Yeah, there is a lot to unpack there—a lot of great information. They're just so cool. So you mentioned a lot of people when they hear "dragonflies," they sort of lump them in the damselflies. What are the difference between these two?

Jessica: There are two different suborders—which suborders are kind of like just human constructs. Right? What's a suborder? It doesn't really mean anything in the grand scheme. But we can kind of really separate those two suborders because, in their juvenile stage, all damselflies have breathing apparatus. They're called caudal lamellae, or gills that are external. And that's where gas exchange kind of occurs. So the damselflies as nymphs look kind of narrow and thin, and then they have these like—what almost like little petals or something like that out the back of their abdomen. And that's through which, you know, they're doing their breathing.

Jessica: By contrast, all dragonflies—in their nymphs, their breathing apparatus is internal. They're called rectal pads. It's in their bum. And so you do not—when you look at—they tend to be kind of stocky, although not all of them. Some of them are kind of sleek. But when you look at the the tip of the abdomen, there's nothing there. There's no external gills, because all of that breathing apparatus is inside of the bum—anal cavity. It's called the anal pyramid or rectal pads. They can also relax their bum and allow water to go into it, and then squirt the water out very quickly as a means of jet propulsion. That's something that that's unique that Anisoptera can do. 

Jessica: And then in the adult stage, damselflies tend to be very slender in their body, and dragonflies tend to be very thick and stocky in their bodies. Damselflies tend to have the wings in the forewing and the hindwing that are similar in shape and size, although not always. And Anisoptera means unequal wing, because dragonflies all have different shape and sizes, forewing and hindwing. That's a pretty big part of their story. Dragonflies in their veins of their wings, they have these little veins that are arranged like a triangle. They're called the triangles. Haha. And in damselflies the veins—similar veins—are arranged as a quadrangle, and it's called the quadrangle. 

Jessica: So, like, there's quite a lot of morphological differences. But the test was: is it actually real? Is it genetically supported as well as morphologically supported? And since people have been sequencing dragonflies and damselflies, we always recover monophyletic damselflies, which means damselflies are a real group that's separate from a monophyletic separate group of dragonflies. So dragonflies and damselflies are indeed—not only are they morphologically different as adults and juveniles, they're genetically different, distinct groups.

Matthew: I was gonna say, it's kind of good to know that the newer science backs up what people had figured out before, which is encouraging.

Jessica: Yeah. 

Rachel: Yeah, definitely. And this is kind of a random question, but how did they get their name? Because they're not flies. And when you think about dragon versus damsel, very different thoughts come to mind.

Jessica: Well, I think for dragonflies, people think that perhaps there was like a translation error when people used to refer to them as kind of devil’s flies. I think it was St. George, maybe, whose horse turned into a devil and took to the sky. And in that legend or in that lore, people thought, "Oh, it's kind of like this insect." And so in the English word—it was translated from Hungarian, I think—what would have been devil's fly into dragonfly. 

Jessica: Whether or not that's true, it's kind of hard to tell looking at linguistics going back through time. But some people—there have been books that have been written kind of on the origin of these names, and that's one thing that people have suggested. For damselflies, I think it's the patriarchy probably. It's just that they're very skinny, and they’re slender, and so people called them damselflies. And that's probably the reason. 

Jessica: The name for dragonflies in other languages, often is very descriptive. Even—a lot of times, there's references to dragons or to their hunting prowess, or for damselflies to them being delicate or like female-like. Those are like in many languages. That's kind of a common theme that we see.

Jessica: And there's family-level names too. Did you guys ever—did anyone ever tell you about darners? Like darners is the common name of Aeshnidae, which is one family. And they have a very long egg-laying apparatus—it's called an ovipositor—which kind of, I guess to some people, look like a darning needle. And so they're called darners because of this like egg-laying apparatus. And my Nana used to say that if we fell asleep near water, that they would sew your lips shut—which they don't do, of course.

Matthew: Haha. Yeah, no. 'Cause one of the names that I've heard for the darners is devil's darner needle. 

Jessica: Yeah. 

Matthew: Yeah. So they do have that association with the kind of darker side of people's minds in a way.

Jessica: Yeah. 

Matthew: Also I was intrigued by St. George! That's an element of the St. George legend that I hadn't heard—that he transformed and flew away. Because I know St. George—I mean being British, and St. George happens to be the patron saint of England. And the tale is always that he was the brave one who went out and slayed the dragon who had been terrorizing the village, and he saved the damsel, you know—which has nothing to do with dragonflies and damselflies, but—. Haha. 

Jessica: Haha! But did something—did his horse take to the sky, though, after being—? 

Matthew: Maybe that's a detail I've forgotten from when I was younger. 

Jessica: Oh, I don't know. 

Matthew: It makes me want to go back and track that down and find out. Now I'm just intrigued.

Matthew:  But yeah. You mentioned 6,400 species, I think, was it? I mean, that seems like a fairly diverse group. But I know that even for people who are just learning about insects, just that level of diversity is pretty overwhelming!

Matthew: I mean part of this is like if someone wanted to go and see dragonflies and damselflies and have a chance to try and pick out the differences between them, where would be a good place for them to go?

Jessica: Well, first of all, I would just say that's around the same number of species as mammals. And we're pretty good at distinguishing mammals. Right? Like, we actually are very good. We're able to do that number of species—to differentiate them—so we probably could do the same for dragonflies and damselflies, is what I would argue. And they can be found away from water, but in general a good place to see them is near water, because the nymphs develop in fresh water. It's because the eggs are laid in fresh water. So females are usually around fresh water for egg laying, and so males are usually around fresh water to mate with females. So you have a pretty good shot—like, if you had a hunch, like where would I find them?

Jessica: It's a pretty good shot of finding them near any type of fresh water. They don't like salt water. Fresh water could be flowing water, like rivers, what we call lotic water—or still water, like ponds or lakes. And then there are some dragonflies, in particular, that are really not picky at all, and they'll be in like temporary transient bodies of water. You leave a kiddy pool on the roof for your building, and they'll lay their eggs there. So some of them you can find even in very surprising areas.

Matthew: Yeah. 'Cause where I live in the suburbs, we're lucky that we have space, although a lot of it is underneath power lines. But there's a creek with beavers established. And so I go out in the summer and seven to eight species of dragonflies wouldn't be unusual for me to see on an afternoon walk, which is just great. And it allows me to watch some of the things they're doing.

Matthew: So I mean, if someone were out at a pond, is—I mean, is seven or eight species—is that a reasonable number to expect or—? And what kind of behaviors might someone see if they're watching?

Jessica: I definitely would say it would depend on your location—where you were. So if you were in like Lagos, Nigeria, or if you were in Georgetown, Guyana, I would say that's not a good number. Haha. But if you're like—I'm from Canada. If you're in Canada, yeah, probably a dozen or so would be not unexpected.

Jessica: Often what you see—often what you'll observe is the things that are territorial. So there are many different families that are found at the water. And some of them, like the darners, are flying high up in the air column, and they're flying fairly quickly. And often they're eating as they're flying, so they do like a lot of turns, you know, as they're looking for food.

Jessica: And so on those ones—so you might see that kind of—we call that hawking behavior. But the things that—those are often—that's not often what draws people's attention. What usually draws people's attention is more near our eye level, on the vegetation. 

Jessica: So around the edge of the pond or the river—wherever you are—often you'll see territorial males that will be perching on like a bit of emergent vegetation. And then another dragonfly will fly kind of near them, and they'll fly around for a while, chasing each other. And then one of them will come back. And what you're witnessing when you see that is this territorial behavior where males are trying to control a small territory that they think—that presumably they've been selected to choose where females are going to to aggregate. Right? 

Jessica: And even if females don't aggregate, it's a good vantage point to kind of stop and look for females. And when males come in to try and take that territory, the males will then fight with each other. And the way that they fight is by flying, banging into each other, chasing each other off. Sometimes you hear the rustle of their wings hitting each other. And then one of them will come back to that perch, because that's the territory.

Jessica: The other thing you might notice is: you might notice males and females together in what we call the copulatory wheel. It looks like a heart, kind of, because—males have their primary penis at the tip of their abdomen. But that's not where the sperm is. The sperm gets moved to the base of their abdomen to their secondary genitalia. So, in order for females and males to have their genitals touch each other, the female actually has to bring her abdomen up to where the secondary genitalia is, and it ends up making this kind of beautiful heart shape. So you sometimes will see these dragonflies flying together in this heart shape. And what that is is copulation.

Matthew: I always find it quite amazing just how much can be seen in a neighborhood.

Jessica: Yeah. I mean, often you can see females laying their eggs as well. Females of damselflies, and of darners, a few other families of dragonflies—they lay their eggs with this ovipositor, this egg-laying apparatus that looks like a little pointy thing at the tip of their abdomen. And they lay their eggs in plant material. So you might see females, either by themselves or with a male kind of guarding them close by, kind of tapping into rotting wood or into the stems of plants or reeds or onto lily pads. 

Jessica: And by contrast, you might see other dragonflies—these are usually in one of two families, the clubtails or the skimmers—that instead are just tapping their abdomen on the surface of the water and then flying away. And that's like a different style of egg laying that we think evolved multiple times, where they don't have an egg-laying apparatus. They just kind of are squirting out clumps of eggs, and it's really fast. And so what you would see if you were standing on the bank is tap, tap, tap, tap, and then them kind of continuing on their way.

Matthew: The other thing that I've seen a couple of times—and it's partly because when I lived in Britain I had a small pond in my garden—is to actually watch the nymphs climb up, and then the adults to emerge, which is just one of those things that when you witness it, it kind of hangs with you, and you just remember it.

Jessica: It is really remarkable that they can even do it. I'm always amazed. It seems like a very risky way to become an adult. Right? Because you pull your adult body out of your larval skin. Your exuvia is left behind. And you're very soft-bodied for a period of time, you know, sometimes a couple of hours. You're incredibly vulnerable to bird predation, frogs, fish—you know, an odonatologist, you know, that comes by. Right?

Matthew: Haha. 

Jessica: Incredibly vulnerable. Because they have to wait for their cuticle to harden up and their wings to kind of unfurl. It's a very—it's a really vulnerable life stage. And so when they make it, I'm always like, "Yeah! You did it. You made it!" Haha. 

Rachel: So you've touched on several parts of their life cycle. And they're just so cool because they transform being aquatic to terrestrial. Can you go through the basic life cycle of a dragonfly?

Jessica: Sure. So they're what we would have called in the past hemimetabolous. They have incomplete metamorphosis. What that means is that they go from an egg, to a nymph—is what we call them because they are in water—and they molt several instars, several stages, and then the final molt is to the adulthood. That's unlike caterpillars or flies where there's a pupal stage. Dragonflies don't have a pupal stage because they have incomplete metamorphosis. 

Jessica: So the egg hatches and a tiny nymph emerges that lasts for a very short period of time, like sometimes less than one day. Then there's an immediate molt which is controlled by the way—what sparks the kind of molt into a larger stage is a hormone cascade. Right? So a little bit more of ecdysone hormone, a little bit more of juvenile hormone at different times, that's what kind of causes this chemical-like cascade that ends up sparking you to molt to a larger size. Usually in the juvenile stage, as they molt to these different instars to a larger and larger dragonfly, they go from eating small, you know, plankton and things like that, to eating each other, to then—they can actually be large enough to eat tadpoles and small minnows in their kind of ultimate or penultimate stages. 

Jessica: And then there is this trigger that is partly probably related to temperature, but we think that they can—that there's some rudimentary time telling that takes place.

Jessica: Dragonflies don't all develop in one year. So sometimes nymphs take five, ten—one person even says that for Petaluridae, maybe almost twenty—years to develop in fresh water. Right? So somehow they're able to kind of count, "This has been one winter, a second winter, a third winter, a fourth winter. It's five years. Boom! It's time to go." We don't understand the mechanism, right? And we don't actually know if it's actually a very set time. And for most dragonflies, given across this, you know, 6,400 to 6,500 species, we actually haven't done studies to really look at generation time. For some things, we know a lot and other things we know almost nothing. 

Jessica: So having said that, whether it's six weeks or ten years that you've been in this juvenile stage, then you have one last molt. And before that molt, the individuals usually crawl up some veg—they crawl up some vegetation. There are reports of them being on the barks of trees. So they can actually leave the kind of pond itself, you know, and kind of go to a nearby tree, or it could just be an emergent reed. And that's when the adult body kind of is pulled out of—it kind of pulls itself—by shunting its hemolymph, shunting its blood, it can kind of pull itself out of this skin, the larval skin or the nymphal skin, and then leave the exuvia behind.

Jessica: In each of the moltings, there is a similar kind of window of vulnerability. So presumably not everybody makes it. Females, when they lay their clutches, they tend to lay quite a few eggs at once—and especially the ones that tap their abdomen on the surface of the water, they don't rely on plant material, and their clutches tend to be quite large. But not everybody makes it, because the eggs, as they drift down, are eaten by frogs and fish. The ones that hatch—birth order matters. If you hatch sooner than your siblings, you're gonna be able to eat your siblings. Right? So there's a lot of unknown about what actually happens to each of the individual, you know, fertilized eggs versus the ones that actually make it. Like, there's probably stochastic chance and randomness and luck that's part of the story.

Rachel: So the incomplete metamorphosis, is there an evolutionary advantage to that? Just thinking— I mean, it must be costly to go from the water, transforming to being on land. Is there any sense that you can give us of how they evolved that way? What's the advantage to that, to just being aquatic, or just being terrestrial?

Jessica: Oh, that's a good question. Well, I would say it's—we don't tend to think of having incomplete metamorphosis as being an advantage, but rather—like to do a 180—it's really that having complete metamorphosis was an adaptation. Because Holometabola, the insects that have complete metamorphosis, are the most successful groups. Almost all the—like, there's a million and a half described insect species—almost all of them are Holometabola. Like, that's where the like hundreds of thousands of species of butterflies, 300,000 to 400,000 species of beetles—like all of that diversity, it's all in the ones that have moved to having this kind of pupal stage. Right? Where there's complete metamorphosis—you know, complete reformation of your internal and external appearance, and also partitioning of resources. So the adults and juveniles usually are eating different things and living in different areas. So you're not competing with your own self. Right?

Jessica: We don't really see that necessarily, in a lot of the insects that have incomplete metamorphosis. A tiny cricket just molts to a larger and larger version until the adult cricket, and they're all kind of in the same environment. But for mayflies and dragonflies, which again are the earliest branching lineages for all of the winged insects, they do have that kind of partitioning where what the adults are doing and what the juveniles are doing are different. They're in different environments. And they're eating different things. And their behavior is really different.

Jessica: I wouldn't—if that was a very successful strategy, we might expect to see that, kind of, in their closest relatives, but we don't. So the sister to the winged insects are the basal hexapods. These are things like silverfish and firebrats, and they are very species-poor compared to the winged insects. Right? There's not very many species of them. And they dry out really easily. I mean, if you have silverfish in your house, you would say that's not true and you're overrun by them because they can be pests and they can be in big numbers. But in general, they dry out really easily. Then you have the mayflies and the dragonflies.

Jessica: And then you have the insects that are in Neoptera the ones that have the basal sclerites, so they can fold their wings behind their back. And there are a few examples of insects that have complete aquatic lifestyles, like water striders or water scorpions or gyrinid beetles, like whirligig beetles. Those live their entire lives as aquatic, in their aquatic state. So it is—that kind of has been a secondarily gained feature in insects. Right?

Jessica: I don't know what the advantage is—I mean, it's hard to say what the advantage is for this partitioned lifestyle, for aquatic and terrestrial, that both mayflies and dragonflies have. But niche partitioning is one hypothesis, where the adult and the juvenile stage—. 

Matthew: Whatever the reason, it certainly works for them. I mean, adult dragonflies are known for being excellent flyers. From what I understand, they can move their wings independently and like fly in all directions. And also when you see then, you see the massive compound eyes with tens of thousands of little eyelets in them. These must be an advantage for hunting. Right?

Jessica: Yeah, vision is a big part of their story for sure, like mantises. Mantises are another group of insects that are very good predators. They're mostly visual predators. Often those two groups are compared—dragonflies and damselflies and mantises—because they both do something similar where they're really using vision as their main way to catch prey. But mantises are kind of—often tend to be sit-and-wait predators, whereas dragonflies are active hunters. So the eyes are like, yeah, definitely, a really striking part of their story. 

Jessica: They can see a lot of color. That's another thing. It's not just that they have all this ommatidia to see what's in front of them, but they actually can distinguish amongst a lot of different colors. And so there's a certain part of a protein called opsins, that allow them to see, you know, in yellows and reds, or blues and greens. And they have a lot of expansion in those families, presumably because they can see a lot of colors. And they have a lot of colors. So it makes sense that maybe if part of their colors are for sexual signaling, right, to communicate with each other, you need to be able to see the signal. So being able to see the lots of colors is probably a big part of their story.

Matthew: Yeah. And the other thing I've heard is: it's almost like they can do math, like trigonometry or something. Because, you know—‘cause you said there's ones that hawk around and fly, but they're also the ones that perch and then chase after stuff. And they don't—if they see prey, they don't launch themselves towards where they saw the prey, they launch themselves in the direction they expect to intercept it. 

Matthew: I mean, do we have any idea of how they do that? I mean, are they really doing math? Or is this just some sort of instinct?

Jessica: Yeah, it's a good question. There was—there have been people who have been focused on this. It was actually two people who were partners of each other, who worked on this for some time—for decades. They did like slow motion videos to kind of really confirm that there was interception-style predation that was taking place. And they looked at the descending interneurons in the brain to try to look at the signals, you know, that were allowing—that were causing certain movement and behavior. 

Jessica: But I think there's still a lot that we don't know exactly. 

Matthew: Sure. 

Jessica: I mean, they don't have a centralized brain as much as they have clusters of ganglia, and so the fact that they're able to do this kind of trigonometry, as you described, is really remarkable. We know some—like when it comes to just hunting prey, and how their trajectory is towards catching their prey. How they do that calculation, we don't really know. And then for longer distance flight questions that we have—like how are they able to migrate across the Indian Ocean and arrive in East Africa all the time? Right? How are they able to stop over in the Maldives.? Right?

Jessica: Some of it might be magnetic fields. Some of it might be that they're sensing different things with light and polarization of light off of the ocean. We don't really know. Like, there's so many hypotheses that have been suggested. And I think an exciting thing about dragonflies and damselflies is that even though they're like beautiful and everybody loves them, man, there's still so much left to know. So if there's people who are like, "Oh, I wonder if I could—," you know, "I wonder if I should go into entomology? I wonder if I should ever study dragonflies?" Like yes please, because we need more people. There's so many questions unanswered that like you could be the one to answer it. Right? There's so many questions left to be posed and answered.

Matthew: Yeah, definitely. And I'm glad you mentioned migration, ‘cause that was another thing that I know a little bit about, mainly because we used to have a project here at Xerces helping to study and understand the migration. And when it comes to insect migration, everybody thinks of the monarch. You know, and it's like, "Woah." And that's wonderful. But then there are other butterflies that migrate in one way or another. And yet the dragonflies are the true global champions. Right? And you mentioned the one across the Indian Ocean, and then I think it goes back up the East African coast. How many species are there that migrate and how do they figure it out?

Jessica: Yeah, there was a group called the Migratory Dragonfly Partnership that was led in part by the late Mike May, that tried to come up with ones that were actually migratory versus ones that just do patrols. They listed, you know, a few. The really famous ones that might come to people's minds are Anax junius which is a darner, a big green dragonfly. And Mike and colleagues glued radio transmitters on them with a mixture of like superglue and eyelash glue, and then like followed them in a helicopter to kind of see where they were going for some short distance. And it did seem like they were kind of doing what we would call migratory behavior. 

Jessica: And since then people have looked at isotopes and looked at stoichiometry and looked at other genetics, and it does seem like they are migratory. We've done a lot of work in my lab on Pantala flavescens, which is the one you mentioned that crosses the Indian Ocean. But we knew a lot about that route, because, of course, people who live in India and in the Maldives and in Africa noticed that they were coming in huge swarms, and they would arrive, you know, at the end of the—the beginning of the rainy season. Then these huge swarms, and I mean hundreds of thousands of individuals, would arrive. 

Jessica: I was fortunate enough to be in India one time when there was a Pantala storm, and it really is—like the stories that people would write in the literature in the earliest twentieth century was about the sky being black. And I mean, I could see why they would describe it that way. That's a lot of individuals.

Jessica: But when we did genetics, it turns out it's not just that they're crossing the Indian Ocean. They're actually crossing all the oceans. So, genetically, you—in order for things to share genes, recently—in recent time, right—it usually is because males and females from those locations have come together and combine the genetic information. So we saw that there was gene flow between, you know, Guyana and South America, Senegal and West Africa, the Andes, Japan, Canada. You know, they were basically sharing genes across the entire continent.

Jessica: There was someone who did work looking specifically at some isolated islands in the South Pacific, and her work suggested that on those isolated islands there actually was some genetic distinctiveness. And maybe that makes sense. Because on isolated islands there also has been observed this behavioral difference where most of these migratory dragonflies in Pantala, when wind passes over the surface—like the top part—of their wings, there's these little trigger hairs, and it causes them to pick up their tarsi, and they get carried by wind. So they migrate 11,000 kilometers, but they're not flapping the whole time. They're largely like gliding on wind—on Intertropical Convergence Zone winds—like winds that go around the equator.

Jessica: But on islands, on Rapa Nui, for example, or in Tonga, they actually crouch down when wind passes over the surface of their wings. Some people, like Samways and Henry Dumont, said maybe that's an adaptive behavior. Because if you're in an isolated island in the middle of the ocean, the ocean is salt water, salt water is death. And you've landed there. You got blown off course from your big migratory storm, you've landed there. Maybe you want to just try and stay there and not get blown out to sea again. And so this, you know—so the genetic work that suggested there was genetic, you know, isolation there, that kind of makes sense.

Jessica: And so we also looked at their wings. So you can—the wings—we talked about how the nymphs develop in fresh water. The wings develop while they're in the water. So the hydrogen in the wings is from the H2O. Right? The water. But the weight of hydrogen varies along a latitudinal and longitudinal gradient. So the weight of hydrogen is different in Alaska than it is in Texas, or than it is in Guinea-Bissau.

Jessica: So you can measure the weight of hydrogen in the wings of dragonflies wherever you catch them. Say you go to downtown Yorkshire, you know, to Manchester, and you catch a Pantala. You can take the wings and measure the weight of hydrogen, and it will tell you whether that was a dragonfly that emerged from water in Manchester, or whether it emerged from water in Japan.

Jessica: And when we did that almost all of the dragonflies that we tested had emerged from a different continent from where we had caught it, which means that they are like big-distance migrators, for sure.

Rachel: Wow, that's amazing.

Matthew: Yeah, that's what I was thinking, too. Because it was the Migratory Dragonfly Partnership that we were part of. And so that's why I knew some of this, but all of that—. I mean, the idea that these broad-winged gliders, the hairs, they sense the wind, and then they just like go, "Okay, and off we go"—haha.

Jessica: Haha. Like, you can look at them very closely, like with a scanning electron microscope for example. And it just looks like a little sensory pit, with a little tiny hair that sticks up. Right? And then, when the wind triggers it, it's inner—I don't know that it's innervated, but I'll say it's innervated, most likely. I haven't done the histology to show that. But, then that's the signal.

Rachel: Wow!

Matthew: Yeah. And I'm endlessly fascinated by insects, and there's always so much to learn. 

Rachel: So overall, how are dragonflies doing in terms of conservation status? Are they declining, like many other insects? And do you have any sense—or do we know why this is happening?

Jessica: So it's a bit of a tricky question to answer. Because on the one hand, in general, yes, they're declining. If we paint with broad strokes, they're declining like all insects are declining, and probably for the same kind of drivers that are causing other insect decline. Water quality is a big part of the story, because a big part of their life is in the juvenile stage in fresh water. And water pollution is definitely an issue. But for adults, of course they're vulnerable to insecticides, and they're vulnerable to land use change and diverting of water and all of those things. So they're definitely being affected in both the nymph and the adult stage.

Jessica: Having said that—and I will say there is a very very active IUCN group that has been monitoring dragonflies for a long time and reporting on status of dragonflies. And what [name] and others have shown would make you feel very concerned. Right? Because we're seeing kind of local decreases that can even lead to local extirpation. And perhaps we can predict that there might be some extinction. But then we also see that there's the—you know, dragonflies are very good at going—at flying. We've just talked about this. Right?

Jessica: So they are also are expanding their range in a way that is faster, some say, than other insects. That also is a complicating factor, because you can have things that used to be further south that move further north. Like, take, for example, there's a dragonfly that used to be found only in like Southern Europe, Northern Africa and now it's established in Sweden. It's been there since the nineties. It's established there. How does that new arrival interact with the existing Northern European species? Right? Is there competition? You know, those are all questions that we're still kind of trying to assess and answer. 

Jessica: So if you look on paper, you might say, "Oh, some dragonflies are doing very well because they're actually expanding their ranges." Right? And so you could say, "Oh, that's a success." Right? But this may not be a success, because many other taxa are contracting their ranges. There's been a lot of work that's been done in the Andes and in, you know parts of the—well, I guess mountain regions everywhere, I would say, but certainly a lot of work has been in the Andes by Cornelio Bota that shows that like there are things that live in the very high altitudes. There's really not anywhere that they can go. 

Jessica: Things from lower altitudes can move up. But the ones that are in high altitudes with climate change—temperature is a big part of it, and humidity is a big part of it, forest fragmentation is a big part of it—you could imagine there could be peril in the future of some of those taxa. There's a giant helicopter damselfly that's really beautiful, enigmatic. It's a spider specialist. Ola Fincke did a lot of work on that taxon. And what it seems is that they're incredibly vulnerable to forest fragmentation because they dry out very fast.

Jessica: She had a student, Emily Khazan, that just released some to see how far they could fly, and they just drop from the sky when they're outside of the forest, right, after a few hundred meters. So it's not just one. It's like—I guess death by a thousand cuts, as Dave Wagner would say. Right? It's water quality, it's forest fragmentation, it's humidity, it's temperature, and so on. And like all insects—dragonflies aren't unique—we don't have enough data about populations.

Jessica: So to really say, definitively—like what the media wants to say, what policymakers want to hear is, "The population went from X, and now the population is X minus one, so you should do this thing and it will bring it back to X." We don't have that baseline data. Not a lot of us are doing population estimates. People do mark and recapture where they put little numbers on the wings of dragonflies. People can use genetics to try and estimate with genomes like historical demography and population size. But we haven't done that for the majority of insect taxons. So we really rely on groups like the IUCN group for dragonflies that are kind of really tracking changes over time and trying to make policy recommendations on that would be a good decision.

Matthew: With all of that in mind, are there things that people can do to help dragonflies—whether that's in their neighborhood or further afield?

Jessica: Yeah, I mean, I would say, like we could all take a page from the British Dragonfly Society, the BDS, because what they have recommended for years is the creation of small ponds, a water feature. Because it's kind of like if you build it, they'll come, you know? Having water features—fresh water is a limiting resource, right, for dragonflies and damselflies, so having water features can be really important.

Jessica: And the British Dragonfly Society actually has tutorials on like how to make a water feature that's small or that's large, depending on what size you have. But for those of us who might be living in Manhattan, that's not really an option. Right? You're not gonna have a water feature on your fire escape. And so then, instead what you might want to do is really advocate for—and this is probably true whether you have a water feature in your backyard or not—but you have to advocate for the people who are in decision-making positions to choose fresh water as a priority. 

Jessica: It's not a national issue. It's not just a local issue. It's like—it's really—it affects all layers of government. Voting is one of the most powerful things that we could do to protect insects, in general. We can turn our lights off to make things better for our nocturnal insects. We can not spray insecticides on our lawns for neonicotinoids, which affect bees. We can do all of those things. But the impact of voting is actually, I would argue, the most substantial and strong impact that a human can have. And when in my town—my town has said, when we have our like candidates discussion before the elections, "Jessica, this is a national issue. Like we can't make—we don't make decisions here in Cranbury.” Yes, we do.

Jessica: A lot of the decisions we make about the way that we maintain our green spaces affect fresh water. We have fresh water in our town. We have a little pond, Brainerd Lake, and a little stream. And the things that we choose about the way that we dredge that water, the things that we stock, all of those affect aquatic insects. Right? It is a local issue, but it's also a national issue, because it actually has really broad impacts, kind of across the—I live in the United States—across the United States. I think that we don't do a great job about advocating to the people who actually have decision making power. Right? We should be encouraging the people who are making decisions to be thinking about dragonflies. It's not out of their realm to think about it.

Jessica: I don't know why—I have—I don't know why everybody isn't talking about insect decline. It should be, I would argue, more important than any of the other topics in some ways, because it affects the survival of humanity. Like humans die without insects. All life dies without insects, really, when you think about how many different animals really rely on insects for a food source.

Jessica: So I would argue, if you can make a water feature, you should, and you could, and it'll beautify your yard. But as an aside, whether you do it or not, please vote for people who care about water and who care about green spaces.

Rachel: I think that was such a good point. And we do talk about a lot of the other issues on the podcast, but I think voting is a really, a really important thing that people can do. And I appreciate that you brought that up, and in such an eloquent way. I feel very inspired now.

Rachel: We’ve so enjoyed learning all of this great information about dragonflies and we are going to end on our favorite question that we ask all of our guests: what inspired you to study dragonflies? And what inspired you to get into this field?

Jessica: Well, I didn't necessarily have like an epiphany that said, "Oh, I should study dragonflies." I always thought they were very pretty. And I spent a lot of time with my maternal grandmother, who, by the way, was from Yorkshire and she lived in Canada, and she lived on a lake so we saw dragonflies a lot. So I already had like a—I started with a positive feeling towards them. But then when I went to—my first undergraduate experience was working with helicopter damselflies with Diane Srivastava in Costa Rica, and that also was a really positive experience. 

Jessica: But I still never thought I would work with them. But then when I was in grad school, thank goodness, I met Dr. Mike May. He was like one of the world's famous odonatologists. He passed away last year, but he said to me—I said, "Oh, they're so cool. But, I mean, of course I can't work on them because everything's already been done." And he was like, "Why would you say that everything's already been done?" And I said, "Well, they’re so cool. They're beautiful. Everybody loves them. They're colorful. I'm sure like all the questions would have been answered already." And he kind of gave the same speech that I just gave to you. Like there's so many unanswered questions. We need more people working on dragonflies. 

Jessica: So, if not for him, I think I wouldn't be here because he really made me see that I could make a contribution. And I think if you're interested in discovery and you like the idea of working in an area where most of the—like odonatologists, we're a pretty fun community-driven group, everyone's really collaborative—you have a chance to discover. It's like going to space, only you're doing it with dragonflies. There's so much left to be done. Once he said that, and once he kind of—it took him a while to convince me of that. But once he convinced me, I mean, I feel so lucky that I get to do this for my job. Haha! It's awesome.

Matthew: That's great!

Rachel: Yeah, that's really wonderful. And I love that you grew up experiencing dragonflies and having a positive experience. We talk about that a lot—just getting kids outside and getting exposure to these incredible animals is so important. So thank you so much, Jessica. I've really enjoyed talking with you and learned so much.

Jessica: Thanks so much for inviting me.

Matthew: Yeah, of course. This was really great. Thank you.

Matthew: Bug Banter is brought to you by the Xerces Society, a donor-supported nonprofit that is working to protect insects and other invertebrates—the life that sustains us. 

Matthew: If you’re already a donor, thank you so much. If you want to support our work go to xerces.org/donate. For information about this podcast and show notes go to xerces.org/bugbanter.