- Look out.

Duck.

Run for cover.

These four wild creatures use chemical weapons for offense and defense.

The mysterious vinegaroon sprays a vinegary blast into the face of hungry predators.

The Arizona Bark Scorpion is powerful, but this cute mouse is basically immune to it.

Attackers beware of the Bombardier Beetles explosive backside.

First, these creatures use a hidden harpoon to inject a fish with venom and swallow it whole.

- Cone snails are striking in more ways than one.

They lurk in the sand around coral reefs and wait till you see what's under the hood.

That pretty veneer is hiding an impressive array of tools and weapons.

A cone snail's breathing tube called a siphon is actually more like a sheet of muscle rolled into a snorkel.

Besides drawing water to gills deep in its shell, the siphon also can pick up the scent of unsuspecting prey.

That's when the cone snail goes spearfishing.

Its extendable proboscis is packing a concealed weapon, a tiny hollow harpoon made of chitin.

The same tough stuff in a lobster shell.

And the end of the proboscis is tricked out with receptors, taste buds that help it close in on its target.

When it strikes, the snail's pace jumps to light speed.

The embedded harpoon doubles as a hypodermic needle to inject the victim with paralyzing venom.

As it reels in the catch, the cone snail uses another covert tool called a rostrum.

It opens up to swallow the fish whole.

Some cone snails hunt more familiar prey, other snails.

The smaller snail digs down to hide its shell opening.

The predator looks for a way in.

When it finds it, the hunter hits its prey with more than one shot of venom.

A lot is going on in the fifth of a second before the snail fires that harpoon.

So let's rewind and break it down.

First, the proboscis flexes as the muscles inside prepare for the strike.

Then the venom floods into the proboscis, but stops just short of the harpoon.

A round muscle holds the lethal fluid in check like a kink in a hose, building even more pressure.

Then everything blows and propels the venom into the harpoon, the harpoon into the prey.

What has scientists interested in cone snails is that their venom varies, not only from species to species, but also from individual to individual and even from shot to shot.

In fact, they seem to mix their venom cocktail on the fly from thousands of unique ingredients, each with its own purpose.

All this variety means a world of new drugs could lie under that shell.

Novel ways to treat things like chronic pain, Alzheimer's, and diabetes.

Most cone snail strikes hurt as much as a bee sting.

A few can kill you though, like this geography cone.

It has the most venomous sting in the world.

Here's a tip.

Don't go gathering these shells when you're snorkeling in Australia.

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How about a little defense?

The reclusive and well-armored vinegaroon has a stinky surprise for anyone who messes with it.

- Late at night, after a rain in Arizona's high desert, a dark shape creeps out from its underground layer.

It's as big as your palm, and it's hungry.

And if it feels bothered.

Okay, what just happened?

And seriously, what is this thing?

A mutant land lobster?

I mean, it's got claws like a scorpion.

The mouth of a spider?

Antenna-like things coming out of its armpits.

A long skinny tail like a rat?

This surprising combo of monster body parts is a vinegaroon, also known as a whip scorpion.

It's in a group of animals called arachnids that includes scorpions and spiders.

But it doesn't sting like a scorpion or hunt with a web like many spiders.

A vinegaroon has its very own style.

This tail may look dangerous, but it's actually a finely tuned sensor.

It picks up vibrations and chemicals in the air.

In this case, to stalk its prey.

Upfront, those antennae looking things are actually specialized legs.

They help the vinegaroon feel its way around.

It's basically blind, so it relies on touch and smell to close in on its meal.

It will break through this cricket's tough exoskeleton with its claws and bristly mouth.

The vinegaroon also uses these wicked claws to excavate its burrow.

Adults and their young use the burrows for protection from predators and to stay out of the scorching desert sun.

Vinegaroons and their ancestors have survived this way for hundreds of millions of years.

So what does it need that spray for?

Researchers observe it by gently holding the animal with forceps.

Despite those frightening looks, this surprising spritz is actually its strongest defense against anything that wants to eat them, like skunks, raccoons, or coyotes.

Even with poor eyesight, the vinegaroon sprays with incredible accuracy.

Inside two pigidial glands, also known as stink glands, holds the foul fluid.

The base of the tail is extremely flexible and can aim the blast in any direction.

Touche skunk.

The instant it sprays, the gland openings appear as two retractable nozzles.

An adult vinegaroon can shoot up to five times before it needs to let its stink glands fill up again.

The spray reeks.

That's because the solution is mostly acetic acid.

The same stuff in the vinegar in your salad dressing, except this cocktail is 16 times stronger.

A blast of that to the face of a larger predator is like pepper spray.

While the vinegaroon's signature defense is unlikely to do any lasting damage, it will certainly leave a lasting impression.

- The Arizona Bark Scorpion has a sting potent enough to send humans to the hospital.

So why isn't this fuzzy mouse afraid of that venom?

- There's an arms race underway in the Sonoran Desert.

Mouse versus scorpion.

Locked in a battle of one-upmanship, each animal evolving better, stronger chemical defenses against the other.

Consider it the Arizona Bark Scorpion.

Its tail contains the most powerful venom of any scorpion in the United States, delivering white hot electrical paint.

This sting sends hundreds of people to the hospital each year.

That venom isn't just potent.

It's sophisticated.

Researchers at the California Academy of Sciences in San Francisco are studying how this venom became increasingly complex over time to deal with the threats scorpions face.

They milk the scorpion.

They use a piece of wax paper to coax it into stinging.

That droplet contains a complex brew of chemicals, including neurotoxins that quickly paralyze prey like this cricket.

But venom also serves as a powerful defense against being eaten.

That's where the mouse comes in.

Do not be fooled by its cuteness.

The southern grasshopper mouse is a ferocious hunter, which is rare among mice.

And it's got a taste for scorpion, which would seem like a death wish, but it isn't.

Scientists at Michigan State University are studying how this battle unfolds, not just physically, but at the chemical level.

This mouse is on the attack.

But the scorpion is not having it.

See how it keeps stinging the mouse?

For any other animal, including you or me, this would hurt badly.

And for a second with the grasshopper mouse, it does.

See how it's rubbing its face?

But after a brief moment of pain, its nerves go numb.

Most animals its size would be dead by now.

But the grasshopper mouse has evolved a specific defense against the scorpion venom.

A protein built into the mouse's nerve cells binds to the toxin.

It blocks it.

Instead of creating pain and paralysis, the toxin does the opposite.

It acts like a painkiller, an analgesic.

After the first couple of stings, the mouse barely feels anything.

Bad news for the scorpion.

Researchers think this trick could point the way to more precise pain medications for people with fewer side effects.

Once upon a time, the scorpion's venom was enough to protect it.

But today in this desert arms race, the mouse has the upper paw, at least for now.

- Next up, get too close and the back end of this beetle will literally explode in your face.

- The bombardier beetle is one of nature's most improbable creatures.

For some, it throws a monkey wrench into the whole idea of evolution.

This beetle is a walking powder keg.

That cloud you see is the result of a lightning fast chemical reaction inside his body.

When attacked, the beetle sets off the explosion, releasing a boiling, hot, stinging poison that sends his enemies running.

He can even aim it.

This potent mixture inside the beetle is made up of three main ingredients.

Mix the first two of them together and nothing happens, but throw in the third and boom.

So the beetle has a trick.

He keeps these ingredients separate inside his body.

From an evolutionary standpoint, that's what's interesting.

In fact, people have been scratching their heads over this for decades.

How did this complex system evolve over time?

Wouldn't earlier generations of beetles have blown themselves up like a bunch of amateur bomb makers?

To some, this beetle's very survival is proof that the whole theory of evolution is wrong.

But it turns out there is a way the system could have evolved gradually.

Remember that third ingredient?

It's an enzyme.

It's like a spark.

It sets the explosion in motion and enzymes evolve.

At first, maybe this one wasn't so dangerous, but gradually it became more potent, more specialized, more explosive, as the beetle's body changed to contain it.

Scientists at UC Berkeley are trying to figure out how this system came together.

They think one of those explosive chemicals evolved from the same raw materials as the beetle's shell.

That happens a lot in evolution.

It's called exaptation, one body part repurposed for something else.

The improbable bombardier beetle, living proof that what doesn't kill you only makes you stronger.