Dragonfly Wings in Slow Motion - Smarter Every Day 91
[Music] Okay, today we're going to try to figure out how dragonfly wings work. So Phil has a dragonfly that I caught last night on our night walk, and we have a high-speed camera, and we are set up with a macro lens to try to collect that exact spot. So tell me when to trigger.
(Phil) Let's go.
(Destin) You got it?
(Destin) Holy cow. - Looks cool, doesn't it? - Oh man. - Yeah? - We got it. - Awesome.
[Music]
(Destin) Alright, so you have one of your entomology books here?
You know it.
Which book is it?
Borro and DeLong's Intro to the Study of Insects. This is a classic entomology book. So with these guys the muscles are actually pulling directly on the base of the wing. So it's a direct flight mechanism. Um...
So what's an indirect flight mechanism?
Indirect flight mechanism, it actually just pulls on the body wall of the thorax and the collapse or expansion causes the wings to then move.
So we're going to go from the rainforest to a rainy day in my hometown. Now, we have all different kinds of art projects here and the one I really want to show you is the dragonfly project. What they've done is they've given metal dragonflies to all the different organizations in the town and they let them paint them however they want.
What I think is cool about the dragonfly is that the wing attaches to the body in a completely different way than most insects. To explain this I've decided to become a dragonfly muscle. This is a wasp. To see how normal insects operate their wings we need to cut the thorax in half so we can see the muscles operating on the inside. Eeugh, it's uglier than I thought.
Anyway, the wings of most flying bugs use this method, which is called indirect musculature. The muscles pull on the body wall of the thorax instead of on the wing itself. The shell then pushes on the wing, which seesaws on a pivot point and moves up and down. The problem is muscles pull - they don't push.
So how does the wing return? If you would've imagined that the thorax was shaped like a football, the big muscles would be squishing the ball in on the middle. When you turn it on its side you can see that this little muscle runs the length of the football and pulls in longways from the inside. This makes the middle bulge back out, which moves the wing down.
Dragonflies, however, operate differently. When we look inside a dragonfly we can see that they have what's called direct musculature. Their muscles pull directly on the wings and are able to operate each wing independently in both directions. This is a big deal, and this is why they completely dominate the insect flying world.
If you look back at the high speed, in those little cracks you can see muscles wiggling and pulling directly on the wings. That's pretty awesome, huh?
(Phil) So, they say "in many Odonata," which are dragonflies, "the front and hind wings move independently, and there is a phase difference in the movements of the two pairs; that is, when one pair is moving up, the other pair is moving down."
Okay, Dr. Jim Usherwood in the UK and his colleagues discovered that because dragonflies have two sets of wings, for the most part they're inefficient. More inefficient than just normal insect flight with two wings. They made a robot with two pairs of wings and they would vary the timing between the two, and they found that at a certain timing they could get 20% more efficiency than they could with just two wings.
Dragonfly wings have something on them called the pterostigma, which is Latin for "wing mark." You may have seen them before. This is a dark cell on the leading edge of the wing that's heavier than the rest of the wing. At a certain velocity, thin wings begin to automatically vibrate, which makes it impossible to glide quickly.
With the added weight at this particular spot on the wing, these vibrations don't start till a much higher airspeed, which means dragonflies can now move much faster. Turns out it's a complex aerodynamic structure built right into the design of the wing to help them glide.
Every time I see a dragonfly I always try to spot that spot. Wait a second, have you ever seen a dragonfly glide?
Okay, in this last video you can see that we're in a canoe, we have a Phantom Miro high-speed camera and we're trying to capture these dragonflies as they lift up off the grass. Now, the cool thing about it is you can see that he uses his wings to hover, but he also uses them as a way of gliding.
It's incredible, 'cause you can see him feather the front wing and allow it to glide the air over the second wing. I've never seen anything like this. Check it out.
[Music]
So I hope you learned something along with us about dragonfly flight. If you've liked us, subscribe to Smarter Every Day.
Please qui... click the flying dragonfly here that my kids are propelling for you, and, uh... you'll subscribe. I'm Destin. You're getting smarter every day. Have a good one.
(Destin) What happened to your tooth?
(Sadie) [Unintelligible] - Don't tell them what I paid for it.
[Kids laughing]
(Destin) [Laughing] Stop. Stop.
Okay, in this last... [Train nearing] There's a train. It's loud everywhere here.
Okay, in this last video we've got the Miro high-speed camera in the canoe and we're looking at a dragonfly, and we get to see it lift up off a piece of grass... [Sniff] Dripping snot. Man. Waiting on dragonflies. It's kind of boring.
[Kids laughing]
Captioning in different languages welcome. Please contact Destin if you can help.