Kids Love Poop. Apparently, So Do Scientists!
A new study about the fluid dynamics of the glassy-winged sharpshooter's "butt flicker" is an instant classic.
“Poop and pee and toots.”
As the father of three kids under 9, this is a commonly heard phrase in my house. You will hear it chanted like a battle cry, sung like a hymn, and uttered in the middle of adult conversation, by an interrupting child, seemingly just because.
“Poop and pee and toots” is a Zen koan—a self-contained story that in five little words sums up all of the states of matter produced by humans in a bathroom (ideally). You’ve got your solids, your liquids, your gases. It wants for nothing.
“Poop and pee and toots!” the children chuckle, as I hand out plates of food, lovingly crafted. “Poop and pee and toots!” I hear while someone is off playing quietly by themselves in another room. “Poop and pee and toots!” they bark when my wife and I are trying to have an important conversation about taxes, our future, or the cosmos.
To which I have to frequently say, “Please, no potty talk,” because I’m the adult in this situation, and I’m trying to create humans that can go out into the world slightly less feral than they are at home.
And yet, this is also me:
And me:
And here I am again:
Here I am, rock you like a hurricane:
All of which is to say, today’s newsletter is going to be about poop. Actually, the fluid dynamics of poop. From a funny little insect known as the glassy-winged sharpshooter. And yes there’s video. And yes, I love it.
And also, please don’t tell my kids.
Singin’ In The Leafhopper Rain
Alright, so what the cuss is a glassy-winged sharpshooter?
While they have an exotic sounding name, sharpshooters are really just another kind of leafhopper, which is a group of insects found all over the world that fits inside the Order Hemiptera, otherwise known as the True Bugs.
(Lots of insects we call “bugs” are not actually bugs, scientifically speaking. Lightning bugs and junebugs are two common examples of this, because both are actually beetles, which means they’re in the Order Coleoptera. True Bugs include things like cicadas, stink bugs [which are actually a kind of shield bugs], bed bugs, leafhoppers, and assassin bugs.)
Anyway, the reason you should care about sharpshooters is because they have a tube for a mouth and they stab that into plants and suck out their juices. And unfortunately, a lot the plants they like to suck are the vines that grow our wine grapes. To make matters worse, once the bugs digest those plant juices, they spray them out of their little bug butts producing something known as “leafhopper rain”.
I actually got to see this in action recently while reporting a story about the invasive spotted lanternfly for National Geographic. (Spotted lanternflies are planthoppers, and thus cousins to the sharpshooters.)
Here’s a short video I took while out in the field with Brian Walsh, a Penn State Extension educator. Look closely, and you can see all that lanternfly goo glistening in the sun as it rains down around us.
Now, when insects squirt their juices in great enough numbers, they can cause a fungal disease known as sooty mold to take hold on the plant’s trunk or roots. Spotted lanternflies do this like whoa, causing the trees they’re sitting upon to look like they’ve been through a forest fire.
Sharpshooters aren’t quite as problematic in this regard—though they are known to spread a disease to grapevines that is definitely not good for us. However, scientists are interested in their secretions nonetheless. And this is why today there’s a brand new study published in the journal Nature Communications which aimed to use “computational fluid dynamics and biophysical experiments” to study “the fluidic, energetic, and biomechanical principles of excretion, revealing how an insect smaller than the tip of a pinky finger performs a feat of physics and bioengineering – superpropulsion.”
Poop and pee and toots, in other words. But make it sciency.
The Sharpshooter’s Mysterious “Butt Flicker”
The wild thing about nature is you can look pretty much anywhere and see something no one understands. That’s how this paper came to be, actually.
A Georgia Institute of Technology researcher named Saad Bhamla—who, by the way, has easily one of the best laboratory websites I’ve ever seen, and I’ve seen a metric cuss-ton of them—was hanging out in his backyard and he happened to notice a sharpshooter take a whiz. Or poo. Or whatever.
The excretion is a liquid, technically, but leafhoppers don’t really have solids, so I think we can get away with either term here.
Anyway, what interested Bhamla was that the insect didn’t just let the liquid dribble out. Rather, it flung the droplet away from its body like it was on fire. And if the sharpshooter was going to all that trouble to rid itself of waste instead of just letting gravity do its thing, then he had a hunch there might be something curious going on inside the bug’s anatomy that would allow for such dramatic poop-flinging.
Of course, Bhamla was right. Upon closer inspection—magnification, high speed cameras—the scientist revealed that glassy-winged sharpshooters possess “a very important biophysical tool called an anal stylus”. Or as Bhamla nicknamed it, the Butt Flicker.
You can think of it like a catapult, though, because once the insect beads up enough of its waste into a tiny liquid cannonball, the Butt Flicker rotates into position, cocks backwards, and then launches the droplet at a force of 40Gs.
Even superhumans like astronauts and Tom Cruise (or the characters he plays in movies) can only withstand a maximum of 9 Gs. Put another way, 40Gs is 10 times faster than the fastest sports cars on earth.
But wait, this story gets even weirder!
After measuring the anal stylus’s speed agains that of the droplet it flings, Bhamla realized that the flinger is actually moving slower than the flingee. Which was weird—they should be going the same speed.
Now, this is where things get a little above my paygrade, but according to the experts, the sharpshooter’s Butt Flicker is somehow able to compress the droplet before launch. This actually stores energy in the form of surface tension, kind of like a diver on the end of a diving board, which then is released as the droplet is flung at just the right moment. And all of that is what allows the poop to fly at 1.4x the speed of the Butt Flicker.
Best of all, the researchers say what they’ve learned may one day help us better shake liquids out of electronic devices, like the Apple Watch you wear to count laps while swimming.
Poop and pee and toots. And fluid dynamics and surface tension and superpropulsion.