Tag Archives: dragonfly

Dragonflies drop their bling when it gets too hot — and climate change spells trouble

The males of dragonflies, like those of many other species, go to great lengths to draw potential mates. In the case of dragonflies, the males developed patches of dark pigment on their wings. Researchers have found that the hotter it gets, the more likely it is for the dragonflies to lose their colorful patches — and climate change could be making dragonfly males less and less attractive.

Credit: Unsplash.

Michael Moore and colleagues at Washington University in St. Louis analyzed hundreds of thousands of dragonfly records uploaded to the iNaturalist community science platform. Overall, researchers looked at 319 North American species and compared them to the animals’ home climates. They found that the hotter the climate was, the more likely it was for the patches to fade away. Conversely, dragonflies in cooler climates often had darker and more elaborate patches.

“Our study shows that the wing pigmentation of dragonfly males evolves so consistently in response to the climate that it’s among the most predictable evolutionary responses ever observed for a mating-related trait,” said Moore, who is a postdoctoral fellow with the Living Earth Collaborative at Washington University.

“This work reveals that mating-related traits can be just as important to how organisms adapt to their climates as survival-related traits,” he said.

As it so often happens in nature, reproduction-related traits come at a cost. In this case, the dark patches can heat up the dragonflies by as much as 2 degrees Celsius (3.5 Fahrenheit), because darker colors absorb more solar energy. So in places that are already hot, maintaining the dark patches becomes harder and harder. As climate change continues to kick in and temperatures continue to rise, researchers expect the patches to progressively grow smaller.

“Given that our planet is expected to continue warming, our results suggest that dragonfly males may eventually need to adapt to global climate change by evolving less wing coloration,” Moore said.

Image credits: Jack Kaminski.

Intriguingly, females don’t seem to undergo the same change. Females can also have colorful patches, but these don’t seem to get smaller in hotter climates. This potentially spells even more problems down the line, because it suggests that climate change won’t just make males less attractive, but it could make females unable to recognize males of their own species, potentially even causing them to mate with the wrong species.

“Unlike the males, dragonfly females are not showing any major shifts in how their wing coloration is changing with the current climate. We don’t yet know why males and females are so different, but this does show that we shouldn’t assume that the sexes will adapt to climate change in the same way,” Moore said.

The findings showcase the sometimes unexpected challenges that creatures face as the planet’s climate continues to heat up. Even dragonflies, the most efficient predators of the animal kingdom, aren’t spared of the effects — no creature is.

The study was published in the journal Proceedings of the National Academy of Sciences

Dragonfly.

NASA plans to send a helicopter drone to Titan in search of life

This Thursday, NASA announced a new mission to Saturn’s largest moon, Titan.

Dragonfly.

Image credits Johns Hopkins / APL.

NASA’s next mission will take it to Titan. The Agency plans to send a drone helicopter the moon to search for the building blocks of life. Christened ‘Dragonfly‘, the mission will launch in 2026 and land Titan-side in 2034. The copter will then fly to dozens of locations across the moon on the back of Titan’s relatively thick atmosphere. Titan is of interest because it is the only body in our solar system (besides Earth) that has liquid rivers, lakes, and seas on its surface.

Fly, dragonfly

“Visiting this mysterious ocean world could revolutionize what we know about life in the universe, ” said NASA administrator Jim Bridenstine. “This cutting-edge mission would have been unthinkable even just a few years ago, but we’re now ready for Dragonfly’s amazing flight.”

The drone will be propelled by eight rotors over a 2.7-year-long mission, during which it will explore environments ranging from “organic dunes to the floor of an impact crater where liquid water and complex organic materials key to life once existed together for possibly tens of thousands of years,” NASA said in a statement. The goal of Dragonfly is to study how far along Titan’s chemistry has progressed towards life. Another point of interest is the moon’s atmospheric and surface properties, as well as its subsurface ocean and liquid reservoirs.

“Additionally, instruments will search for chemical evidence of past or extant life,” the statement adds.

The craft will first land on Titan’s equator to explore the region, and will then move around the area in short trips. A series of flights 5 miles- (8 kilometer)-long are also planned after that, to get the drone to various points of interest around Titan. It will collect samples at these points, and then make its way to the Selk impact crater, where there is evidence of a possible ‘primordial stew’ of liquid water, organic materials, and energy. All in all, the lander will eventually fly more than 108 miles (175 kilometers).

Titan’s atmosphere is made mostly of nitrogen, like Earth’s, but is four times denser. Its clouds and rains are methane, which pool into hydrocarbon lakes on the surface. The moon’s underground ocean, however, could harbor life as we know it.

How the dragonfly got its wing patterns

Researchers used a new algorithm to calculate how one of the most intricate and delicate patterns in the natural world developed: the dragonfly wings.

The hindwing of a dragonfly. Dragonflies are among a group of insect species that have a complex network of veins, partitioning the wing into hundreds or thousands of small, simple shapes. The shape and position of these secondary veins are endlessly variable, generating unique patterns on each individual wing. Image credits: Harvard University.

Dragonflies have been around for 200 million years, and they’ve developed some remarkable features. For starters, they’re fierce predators, widely considered to be the most efficient predators in the animal world. Dragonflies are also agile fliers, with powerful wing muscles and a robust physical constitution. Sure, the wings seem very delicate and fragile to us, but at the insect scale, they’re truly powerhouses.

The wings of dragonflies also feature remarkably intricate patterns, which have puzzled researchers for quite a while. Each pattern is unique, but the reason why complicated patterns form (like leopard spots or zebra stripes) is still not exactly clear. So Harvard researchers set out to develop a framework for understanding how they form.

They compiled a database of more than 500 specimens from 215 different species of dragonflies and damselflies (a closely related group), “teaching” the algorithm to differentiate each individual shape made from the intersecting veins on the wings of the insect.

A differentiated, or segmented, wing outlining each individual polygonal shape made from the intersecting veins. Image credits: Harvard University.

The authors found that while every pattern is unique, the general distribution is remarkably similar across families and species. Based on this finding, the researchers built a developmental model for how these patterns can be formed.

They found that by inputting only a few simple parameters, they can determine the formation of complex patterns, similar to what is observed in nature.

Scientists tested the algorithm on several species, even some distantly related insects, finding that every time, it generates life-like reproduction of wings.

Dragonflies and damselflies have particularly elaborate vein patterns. The researchers compiled a dataset of wings from 232 species and 17 families of dragonflies and damselflies. Image credits: Harvard University.

Researchers also propose a reason why the patterns develop this way, though this has not been verified yet.

They believe the primary veins follow a regulated distribution pattern. From these veins, an inhibitory signal diffuses from multiple signaling centers. These inhibitory zones emerge randomly and repel one another, further preventing secondary veins from growing in certain areas. This already creates complex patterns, and as the wing grows and develops, it creates the complex geometries of the veins.

The study has been published in PNAS.

Drone Explorer.

Dragonfly dual-quadcopter drone proposed to explore Titan to understand how life appeared

A new explorer joins the ranks of proposals for NASA’s New Frontiers initiative. Christened Dragonfly, this nuclear-powered robotic dual-quadcopter will take advantage of Titan’s thick atmosphere and low gravity to hop about the moon and beam back data from potentially habitable sites.

Drone Explorer.

Image credits JHUAPL/Mike Carroll.

Saturn’s largest moon, Titan, is quite an exciting place for scientists trying to understand how life develops. It has enough water to be comfortably called an ocean world. To be fair it’s frozen solid on the surface, but the interior seems to be a relatively warm, liquid ocean. It also has a diverse chemistry rich in the building blocks biology (as we know it) needs. Put the two together, and what you get is a place with a lot of organic material undergoing the same reactions that we believe went down in Earth’s early days.

All in all, it’s a place that could offer us insight into how life appeared that lab work simply can’t provide. So what NASA wants to do, as part of its New Frontiers exploration program, is to send a pair of eyes to Titan and see what’s what. That pair of eyes, engineers at the Johns Hopkins Applied Physics Laboratory believe, should come in the shape of a dual-quadcopter they named Dragonfly.

“This is the kind of experiment we can’t do in the laboratory because of the time scales involved,” said APL’s Elizabeth Turtle, principal investigator for the Dragonfly mission.

“Mixing of rich, organic molecules and liquid water on the surface of Titan could have persisted over very long timescales. Dragonfly is designed to study the results of Titan’s experiments in prebiotic chemistry.”

The drone explorer will carry an array of instruments to any points of interest across the moon’s surface. For this mission, flying sticks out as an ideal method of transportation. Given Titan’s dense atmosphere and low gravity, flying is much easier to do here than on Earth. This means Dragonfly will be able to carry more instruments with the same effort, and flying will let it navigate rugged terrain much faster and with less risk of damage than wheeling about the place.

At every site, the drone will sample atmospheric and surface chemistry with a suite of instruments. This data will allow scientists to estimate the habitability of the moon, see how far Titan’s chemistry has progressed towards biotic chemistry, even pick up eventual traces of water- or hydrocarbon-based life. Mass spectrometry will reveal atmospheric and soil composition, gamma-ray spectrometry will be used to probe into the chemical composition of the shallow sub-surface. A suite of meteorology and geophysics sensors will record wind, pressure, temperature, seismic activity, as well as a host of other factors. Finally, a camera will let scientists peer at the nature of the moon’s surface.

“We could take a lander, put it on Titan, take these four measurements at one place, and significantly increase our understanding of Titan and similar moons,” said Dragonfly project manager Peter Bedini of APL.

“However, we can multiply the value of the mission if we add aerial mobility, which would enable us to access a variety of geologic settings, maximizing the science return and lowering mission risk by going over or around obstacles.”

Later this year, NASA will select a few of the proposals for New Frontiers for further study. Sometime in mid-2019, one will be selected to become the fourth mission in the planetary exploration program.

A moorland hawker dragonfly. Credit: Wikimedia Commons.

Female dragonflies play dead to fool unwanted suitors

For the first time, researchers have caught female moorland hawkers playing one of the oldest tricks in the book. While out in the Swiss Alps, biologist Rassim Khelifa from the University of Zurich witnessed how a female simply crash-dived to the ground while a male pursued her. The female stayed motionless on the ground until the poor male suitor left, then took off once she was confident the male had lost interest.

A moorland hawker dragonfly. Credit: Wikimedia Commons.

A moorland hawker dragonfly. Credit: Wikimedia Commons.

‘Hey, gorgeous!’

‘I’m just gonna drop dead now’

Khelifa has been studying dragonflies for more than ten years but never came across this odd behavior. But when he and colleagues took a systematic look, they found 27 out of 31 surveyed female moorland hawkers (Aeshna juncea) played the same trick plummeting to the ground and playing dead to avoid suitors. The ruse didn’t work all the time, as only 21 of the ploys were actually successful, as reported in the journal Ecology.

For these female hawkers, it’s not just about forgoing sex when they don’t want it — it’s about the survivors of their offspring. A single sexual encounter with a male is enough to fertilize all of a female hawker’s eggs and copulating again would destroy them. Unlike other species dragonflies, after the male copulates with the female, he makes a run for it never to return. Males from other dragonfly species typically tag along with the female to protect her against rival suitors.

This explains why the female hawkers basically need to play dead as a last resort to avoid male coercion. That’s when hiding in the dense grass near ponds doesn’t work.

Though rare, this isn’t the first instance of an animal feigning death to avoid suitors. According to New Scientist, two species of robber fly, a type of mantis, a species of spider all do it too. What they all have in common is they all lay eggs, which is why Khelifa wants to investigate how widespread this behavior really is.

 

 

Composite image of dragonfly carrying retroreflective markers. The markers are used to measure the orientation of the dragonfly’s head and body during flight. The data from the measurements allows the underlying steering strategy to be inferred. Credit: Igor Siwanowicz, Leonardo Lab, HHMI/Janelia Research Campus

Dragonflies hunt prey like dancing a ballet, similar to the internal model used by humans

Arguably the most efficient predator in the world today is the dragonfly, which boats a 95% success rate. Obviously, there’s more to the dragonfly than meets the eye or more than you would expect from some random insect, at least. One of the reasons it’s so successful may be due to how the dragonfly moves in response to its prey, guided by an internal model similar to that used by us humans. In effect, the dragonfly performs complex calculations that include both the prey’s current position and predictions of its future position.

An exciting choreography

Composite image of dragonfly carrying retroreflective markers. The markers are used to measure the orientation of the dragonfly’s head and body during flight. The data from the measurements allows the underlying steering strategy to be inferred. Credit: Igor Siwanowicz, Leonardo Lab, HHMI/Janelia Research Campus

Composite image of dragonfly carrying retroreflective markers. The markers are used to measure the orientation of the dragonfly’s head and body during flight. The data from the measurements allows the underlying steering strategy to be inferred. Credit: Igor Siwanowicz, Leonardo Lab, HHMI/Janelia Research Campus

 

The dragonfly only needs half a second from the moment it first sees an unsuspecting prey until it finally swaps it up from beneath (this is how the dragonfly always operates to avoid being seen). Biologists knew the dragonfly is an efficient, and awesome I might add, hunter but the complexities of its behavior escaped them. According to scientists at  Howard Hughes Medical Institute’s Janelia Research Campus, dragonflies on the hunt perform internal calculations every bit as complex as those of a ballet dancer.

You might be surprised to know what great deal of effort and how billions of computations are made automatically by your brain every second just to pick up… a cup of coffee.

“You have an internal model of how your arm works, how the joints are articulated, of the cup and its mass. If the cup is filled with coffee, you incorporate that,” Janelia group leader Anthony Leonardo explains. “Articulating a body and moving it through space is a very complicated problem.”

For many years, Leonardo has been studying how the nervous system triggers actions in response to environmental stimuli, like when an animal quickly enters escape mode when it senses it’s been hunted. Dragonflies are particularly appealing for his research because he wants to know  whether the same stimulus-response loops  underlie more complex behaviors.

“The idea was the dragonfly roughly knows where the prey is relative to him, and he tries to hold this angle constant as he moves toward the interception point. This is the way guided missiles work and how people catch footballs,” Leonardo says. But there was reason to believe prey capture was more complicated.

“You don’t need a spectacularly complicated model to guess where the prey will be a short time in the future,” he says. “But how do you maneuver your body to reach the point of contact?”

The dragonfly doesn't only have a fantastic response time during attack. It's well suited for escape too, leaving predators with their tongues hanging.

The dragonfly doesn’t only have a fantastic response time during attack. It’s well suited for escape too, leaving predators with their tongues hanging.

But how do you keep up with such a fast and tiny predator? Inspired by the same techniques used in the movie business to translate the movements of actors into 3D animations, the researchers placed reflective markers on key articulated areas of the dragonfly – the head, body, and wings. A high speed cameras recorded the reflected flashes as the dragonfly  chased after either a fruit fly or an artificial prey – a bead maneuvered by a pulley system. The positions of the body and head were most revealing.

dragonfly

Take #2.

It was soon clear that the dragonfly wasn’t only responding to its prey’s movements; it also made structured turns that adjusted the orientation of its body, even when the prey trajectory didn’t change.

“Those turns were driven by the dragonfly’s internal representation of its body and the knowledge that it has to rotate its body and line it up to the prey’s flight path in a particular way,” Leonardo says.

These shifts are aimed to disorientate its prey, yet during this whole process the dragonfly never loses sight of its target. Surprisingly, the scientists found that each dragonfly moved its head to keep the image of its prey centered on the eye, despite the rotation of its own body.

“The dragonfly is making a lot of turns to line itself up. Those turns create a lot of apparent prey motion. If the whole world is going to spin, how can it possibly see its prey?” Leonardo asks.


Leonardo says the movements his team observed are so fine-tuned that they keep the image of the prey fixed in the crosshairs of the dragonfly’s eyes—their area of greatest acuity—during the duration of the chase. That allows the dragonfly to receive two channels of information about its prey, Leonardo says. The angle between the head and the body tracks the predicted movement of the prey, while the visual system detects any unexpected movement when the prey strays from its position in the crosshairs.

“It gives the dragonfly a very elegant combination of predicted model-driven control and the original reactive control,” he says.

Findings appeared in Nature.

 

Article suggests dragonflies are the most effective predators in the animal world – 95% success rate

Lions roar and act tough, and they’re often regarded as kind of the land, but only 1 in 4 of their hunts is successful. Sharks have been on top of the food chain for hundreds of millions of years, and still half of their attempts fail. Dragonflies on the other hand, look soft and fragile, and are among the few insects which people generally believe look nice – but they are voracious predators, and may very well be the most efficient hunters in the animal kingdom.

dragonfly2

They snatch their prey mid air with shocking precision, 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.”

What does a dragonfly do after it eats? Usually, goes to eat some more – their appetite is just bottomless apparently. 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.”

dragonfly3

In a series of recent papers, researchers have pinpointed key features of the dragonfly’s brain, eyes and wings that allow it to hunt so much without failing; one team has shown that they have an almost human-like ability for selective attention, being able to focus on a single insect from a swarm, just as a man at a party focuses on his date, ignoring the background buzz.

In other research, 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 – this neural pathway enabling it to track a moving target, calculate the interception trajectory and subtly adjust its own path as needed in the process. Apprently, they also use old sailor tricks.

As any experienced sea wolf will tell you, if you’re on a boat, and you see another boat moving at an angle relative to you, and as you approach, the angle doesn’t change, the two of you will crash. The dragonfly does the same thing – it moves in closer to its prety, but always seeing it on the same spot on the retina, keeping the angle constant.

“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.

Entomologists have shown that this isn’t an active type of hunt, but rather an ambush.

“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.”

The fact that they’re perfectly adapted for flying and hovering also helps them. They’re able to reach speeds of 50 km/h with only three wing beats, dive, fly backward and upside down, and pivot 360 degrees.

“A dragonfly can be missing an entire wing and still capture prey,” Dr. Combes said.

Full study here.

GeoPicture of the week: Giant Dragonfly fossil

dragonfly

This is a Cast of an original fossil of a Meganeuridae. If you’re scared of dragonflies, brace yourself for this: these extinct insects from the Carboniferous period measured up to 70 cm. They are the largest known species of flying insect.

Controversy has prevailed as to how insects of the Carboniferous period were able to grow so large, especially considering that there is a fixed upper limit placed on insects, based on the way oxygen is diffused through the insect’s body via its tracheal breathing system.