[MUSIC] If this is your first time in the rainforest, I get it.

All the trees pretty much look alike.

Maybe you're at the end of a long hike, you wanna take a little break, have a drink of water.

So you pick a tree to rest up against and relax.

Well, this would be a very bad tree to pick.

It's full of ants.

We've got ants in our plants!

[MUSIC] Flowering plants first sprouted onto the scene about 160 million years ago, and they've been locked in a dance with insects ever since... sometimes they give food, sometimes they are food, their evolution's always been intertwined.

But the most complex insect/plant relationships don't involve butterflies, beetles, or bees.

They belong to the ants.

Locals call this the "novice tree" because there's a painful lesson waiting for anyone who leans up against it.

It's full of ants.

A whole colony lives inside, spread from the roots up through the highest branches.

But inside of a tree is kind of a weird place to find ants.

If only there was somebody around who could teach me more about this crazy ant/tree relationship!

Oh!

Oh, look at that!

It's Aaron Pomerantz!

Here in the rainforest.

How's it going, Joe?

It's going pretty well, but I'm kind of curious why ants would want to live inside a tree?

Where we're from ants live in little mounds, and that's just how it goes Yeah, this tree can host thousands of ants, and this is not a short term relationship.

The ants can live inside as a colony for years, for decades even, and their tree grows as the colony grows.

You can see that they're sort of coming out of these little pits, right?

Yeah, there's holes all up and down this tree where the ants coming in and out.

Yeah and if you were to cut this open or one of the stems, they would actually be hollow, the ants live inside.

That's right.

To these ants, this tree is home.

And the ants didn't tunnel it out themselves.

It grew that way.

A tree built for a queen and a few hundred thousand of her children.

Inside, the ants not only get a safe place to raise their young, the tree is also their food source.

Tiny scale insects live alongside the ants.

In return for free room and board, those bugs digest tree sap and secrete a nutrient-rich liquid, full of the good stuff ants need.

They're kind of farming them like little mini insect cows.

That's an adorable... they milk them?

Little udders!

Yeah!

But you have to wonder: what's in it for the tree?

Why spend all that energy building tunnels and doors so a bunch of insects can move in and suck out your precious bodily fluids?

Because ants are very protective of their home.

It's really interesting to note we're in this barren spot right now.

You notice there's no other plants around us.

And this is caused by the ants, they actually clear out parts of the rainforest because they want their tree to get more sunlight so that it can grow.

Think about that.

If a branch or vine from another plant touches their tree, they'll sting it, bite it, and cut it out of the way, like tiny gardeners.

Both species put in work, both species get something in return.

Good old mutualism!

Plants that house ants are called myrmecophytes.

But not all plant/ant relationships are so evenly balanced.

Acacia trees house ant bodyguards that are so aggressive they can repel an elephant, and in return, they get nectar.

But the tree laces that meal with an ingredient that keeps the ants from digesting nectar from any other plant.

They're chemical slaves to their host.

Now one tree of ants is cool, but we found another species that takes treehouses to the next level.

Aaron this is weird over here, we've been walking through dense rainforest all day long, but we're in a clearing, we're not dodging branches, there's sun above us, what's happening here?

Yeah, this is a really strange part of the forest that we're in right now, and this is called the Devil's Garden.

The Devil's Garden, like did people come through and clear this out?

Is this clear-cutting in the forest?

It's actually entirely caused by ants that live with this plant.

What they're doing is they're clearing out all the space around it and only letting their home plant survive These plants grow little bulbs called domatia, little ant houses!

To keep the ants happy, the plant pumps out pre-packaged meals called food bodies.

And in return, the ants offer protection.

Just like tiny Ant-ony Sopranos.

Think about how weird that is.

This plant grew these hollow bulbs seemingly for those ants without even knowing that ants exist.

And in return that plant gets protection from things like caterpillars that might want to eat its leaves and those ants get protection by being up off the rainforest floor, where there's things like spiders and flies that want to lay eggs so maggots can eat their brains.

It's a real "you scratch my back, I live inside your hollow bulbs" relationship/ And they're clearly very successful at it, because the ants will climb out of their little homes, onto the ground and just destroy any other competing plants in the area.

They're really active, they're out all over this right now, I think they think we're plants that are trying to come in here and grow.

So they come down onto the forest floor, do they like eat, do they chop them down like leafcutters?

How do they control that growth?

So it's really cool, they'll actually inject, with their stinger, formic acid into the plant, which sort of melts it away kind of like this herbicide.

Yeah, all along this root I see those little black ants from the tree.

They've wiped out this little seedling here.

It's dry and crackly and dead, they're doing forest control right before my eyes.

The line between cooperating and being a parasite is like this thin.

If these yellow Allomerus ants move in, they castrate the fruits, so instead of devoting energy to reproduction, the plant produces more food and shelter for the ants.

Fun fact: this plant is also known as "huevo de gato", which I'll let you translate yourself.

Adios huevos.

That's so awesome that some of the rainforest's smallest residents can shape it in such incredible ways.

Yeah, the ants are the dominant life force out here in the rainforest, it's incredible.

Yeah, I found that out the hard way, but man thanks for showing us that, that is so cool.

Alright, stay curious!

Um, I thought of a joke.

What did the Pink Panther say when he stepped on an ant mound?

What's that, Joe?

Dead ant, dead ant, dead ant dead ant dead ant!