The fascinating physics of insect pee | Saad Bhamla (re-release)

Elise Hu (0:00)

Where I live, October means pumpkins on porches and fake cobwebs stretched across just about every bush. My family has been planning their Halloween costumes for weeks. It's a holiday with ancient roots, and plenty of cultures around the world have their own traditions for honoring the dead and the mysterious. But whether or not you celebrate, it's a fun time to lean in to the strange and the spooky. For October's TED Talks Daily playlist, we have gathered five haunting talks covering everything from grieving crows to zombie roaches. They might give you a few chills, but they're also full of weird, wonderful discoveries that remind us just how fascinating our world is. Happy listening.

You're listening to TED Talks Daily, where we bring you new ideas to spark your curiosity every day. I'm your host, Elise Hu. Today, scientist Saad Bhamla dives into his research about insects. But not just insects broadly. In his 2021 talk from TED Monterey, Bhamla shares the discoveries about one particular insect behavior he hadn't previously seen and I hadn't previously thought about until hearing this very talk after a short break.

And now our TED Talk of the day.

Saad Bhamla (1:24)

I love bugs. I think of them as nature's tiny engineers, because they come up with the most extraordinary and incredible solutions to life's problems. And I just love observing them because they're so full of surprises and curiosities. During my career, I studied spiders that use their webs as a slingshot to capture prey deep in the Amazon rainforest, worms that tangle up with each other and form knots to form these shape-shifting blobs to survive in harsh environments such as sewers and caves, and tiny aquatic beetles that bring their own scuba gear when they dive on their butts.

But today, I'm going to tell you a story about one of nature's most extraordinary engineers that pushes the limits of fluid mechanics and bioengineering, and arguably solves their number one problem.

How insects pee.

A few years ago, my student, Elio Cholita and I, observed this tiny insect having a private moment in our own backyards in Atlanta. And we couldn't believe our eyes. This insect was peeing for hours, and it was so quick, we could barely see it. And we were blown away. We had never seen anything like this. We had never seen an insect pee. So today, I'm going to tell you how insects pee, why they pee so much and in this way, and finally, why you should care about insect pee. So sit back and relax. You're in for a treat.

So one of the first things we had to discuss is, wait a second, insects pee? And turns out that almost all insects pee in one form or the other, it's a closed system. What goes in must come out. But the protagonist of today's story, homilidiska vitripenis or a glassy winged sharpshooter. And this insect specializes in feeding on xylem fluid from plants. It's a sap sucker, but I think of it as a plants mosquito. And just after a mosquito sucks your blood, it leaves behind a parting gift. So do these sharpshooters that spread bacteria into these plants. And it causes devastating and deadly diseases in plants, killing them. This is a huge problem in agriculture, including here in California, where they cause millions of dollars in damage to vineyards. We realize that this insect forms a droplet of pee, and then it flings them at extreme accelerations of 40G forces. That's 40 times faster than the sprint of a cheetah. These insects are really packing a punch from their butts.

We wanted to take a closer look at this flicker, so we put this insect and took a look under a microscope at its business end, and this beautiful structure has a scientific name. It's called a butt flicker.

And this is what we discovered. We realized that this insect had evolved springs and latches just like a catapult so that it could efficiently hurl its droplets of pee repeatedly at these high accelerations. Now, we wanted to measure the speed at which this flicker was moving and the droplets, so we measured the speed of both. The droplets and the flicker, and this is where we made a puzzling observation. The speed of the droplets in air was faster than the flicker. So if you take a ratio of that, we were expecting it to be 100 percent, but turns out that the speed of the droplets are about 150 to 200 percentage faster than the flicker itself. This is why this is counterintuitive. Imagine a Yankees baseball player throwing a ball at 100 miles an hour. At some point during that throw, the hands and fingers are moving at 100 miles an hour. Say an amateur ball player throws a ball at 50 miles an hour, and if you measure the speed of the ball and it's 100 miles an hour in mid-air, we'd be surprised. Where would that extra speed come from, right? This is exactly what these insects are doing. So to solve this puzzle, we went back and looked at our videos. We realized that unlike a baseball that's rigid, these droplets due to surface tension, these tiny droplets are squishy. And we had an aha moment. We were wondering if this insect is storing energy due to the surface tension just before launch. And to test this, we did naturally what any of us would do. We converted our kitchen tables into a lab to test this. So now we're going to place droplets on a speaker to squish them at high speeds. And this is what we discovered. We realized that water that flows in our faucets, like a liquid at these tiny scales due to surface tension, with the right timing, can get a kick, store energy, and if you time it just right, you can launch these off at extremely high speeds, just like a child on a trampoline. And to test this idea of timing, we even built a catapult, or should I say a catap-pee.