Why a Panama katydid turns green from hot pink

HostI was looking at some photos of bugs and I saw one that looked like it had been dipped in neon paint. It was a katydid, which usually looks just like a green leaf, but this one was bright, bubblegum pink.

HostIt seems like a terrible way to hide in a forest, so how does being that bright help a tiny bug stay alive?

GuestIt does look like a big mistake. If you're a small bug and you're bright pink in a world of green, you should be an easy snack. But in the forests of Panama, these little guys are born that way on purpose. They spend their first few weeks of life looking like a piece of candy, and then, as they get bigger, they slowly turn into a deep, leafy green. It's not a mistake at all. It's a very clever way of hiding that changes as they grow. They aren't trying to hide on the big green leaves yet. They have a different home in mind when they're small.

HostBut pink is the opposite of hiding. Where do they go where a hot pink body actually blends in?

GuestWell, think about what a forest looks like. It isn't just old, dark green leaves. When new plants are just starting to grow, or when new leaves sprout on the tips of branches, they often aren't green yet. They can be bright red, or orange, or even pink. These colors show that the leaf is still fresh and hasn't filled up with the green stuff that turns sunlight into food yet. So, when these katydids are tiny babies, they hang out on those new, red leaves or inside flowers. To a bird flying by, that pink bug blends right in with the red and pink buds. They aren't hiding on the green parts of the forest. They're hiding on the new parts that match their skin.

HostOkay, but those new leaves don't stay pink for very long. They turn green pretty fast. Does the bug just have to hope its timing is perfect?

GuestThat's the big risk, but the bug is growing just as fast as the plant. They stay in that pink stage while they're small enough to sit on those little buds. But as the bug grows, it gets too big to hide on a tiny flower or a new leaf tip. It would start to hang off the edges, and then the pink color would be a problem. So, as the bug gets bigger, its body starts to produce a green color. By the time it's an adult and it needs to sit on big, old green leaves to find food and mates, the pink is totally gone. It turns into a perfect copy of a green leaf, right down to the veins and the little brown spots you might see on a real plant.

HostSo it's like they have two different outfits for different times in their life. But if they can turn green, why not just be green from the start?

GuestThis is where it gets really interesting and a bit backward from how we usually think about nature. For a long time, people thought pink was a rare mistake, like being born with no color at all. But some people who study these bugs found that pink might actually be how they all want to start out. In the instructions their bodies follow, being pink is the easy path. It's the default. Turning green is actually the hard part. Their bodies have to do extra work to create that green color to cover up the pink. It's almost like the green is a coat of paint they have to put on as they get older.

HostWait, that's confusing. If being pink is the easy way, wouldn't every bug be pink? Why don't we see them everywhere?

GuestMost bugs have a switch in their body that tells them to make green color so they can hide. In these Panama katydids, that switch is timed to turn on only as they get older. If that switch fails or gets stuck, the bug stays pink its whole life. We call that erythrism. It's a big name for a simple thing: the red and pink colors show through because the green stuff never showed up to work. They have just found a way to use that easy pink path to their advantage while they're young and small. It's a way to turn a basic trait into a survival trick.

HostSo they aren't choosing to be pink; they just haven't put on their green coat yet? But they still have to find the right leaf to match.

GuestRight, they have to be very picky. If a pink baby lands on a big green leaf by mistake, it's in big trouble. They have to stay on those tiny, colorful spots or they're gone. It's a high-stakes game. They're safe as long as they stay in their tiny, colorful world, but the moment they wander onto the green, the rules change. It's a total shift in how they live. They go from being a flower-mimic to a leaf-mimic. They spend their whole lives trying to look like anything other than a bug.

HostIt's a lot of work just to stay hidden. You start out as a bright little gem and end up as just another leaf in the woods.

GuestThe real trick is that being pink is the only time they get to be themselves; they only put on the green mask when the world gets too big to hide in a flower.

HostThat pink bug isn't a mistake or a neon sign; it's just a baby waiting for the right time to turn into a leaf.