Original subtitles

Our world is not always the same.

Hidden from our view, lies a different world.

Creatures utterly unlike us.

Almost alien.

Yet, they are more numerous than any other group on the planet.

Welcome to the fascinating world of the arthropods.

Spiders, scorpions, and insects.

Today, we have new camera techniques that will allow us

to reveal in greater detail, than ever before, their lives -

the way they fight, and feed, and reproduce.

This series uses specially developed 3D camera technology

to study the micro world in extraordinary detail,

both on location and in specially constructed environments.

We'll witness their births, the challenges they face,

and the moments when their lives hang in the balance.

And that may help us understand how it is that, today,

over 80% of all animal species on this planet are arthropods.

In this series, we'll see the way they have evolved,

from the comparative simplicity of the millipede, to vast

colonies that contain hundreds, even millions, of individuals.

We'll witness the most extraordinary

transformations in the animal kingdom.

We'll meet ants that farm,

spiders that can casts their webs...

..and the bug that wears the bodies of its victims as a disguise.

Welcome to a strange and dangerous world.

The tropical rainforests of Africa are teeming with a huge

variety of insects.

And with so many bugs around, you might think that finding

a mate would be easy, but you would be wrong.

Courtship is often, complex, protracted, fascinating,

and, for some, even brutal.

This is a Goliath beetle - one of the biggest of all insects.

I know that he's a male, because he's got these two

horns on the front of his head, with which he battles for females.

Goliaths are among the strongest insects in the world.

This male can lift 850 times his own body weight -

the equivalent of you or me lifting ten elephants.

He'll need all his strength to win the right to mate.

The female has no horns.

She doesn't need them.

It's the males that do the fighting.

They face off - each assessing the threat the other may pose.

It's a savage battle,

with each trying to hook his horn under the other's shell.

If one of the males flips his opponent off the branch,

he'll have the female to himself.

The loser retreats.

And, with the duel over, the winner gets the mate.

On the floor of the South American forest,

it's all about touch and smell.

Sight is not much use to bugs that live in the undergrowth.

This male Chilean rose tarantula is almost blind.

He searches for a mate using smell, and, when he's close enough,

by touch.

Right now, he's on the trail of a female, and he's come prepared.

Before he set out, he wove a silk mat, deposited sperm on it,

and sucked his sperm into one of his palps -

a finger-like appendage close to his mouth.

This female has signalled her presence to him

by emitting a sex hormone.

And he approaches.

He pushes himself beneath her.

Special hooks on his front legs hold her fangs aside

to prevent her biting him.

His movements also stimulate sensitive hairs on her underside.

And, with this, she yields, and he uses his palps to fertilise her.

When she lays her eggs, the offspring will all be his.

In North America, there's a male with far less time to find a mate.

He is a nasonia jewel wasp, and he's no bigger than a match head.

He only lives for two days, so his entire,

short life is devoted to mating.

And with so little time,

he has an unusual way to ensure that he's successful.

When he finds a female, he smears a sex hormone on her antenna.

If she finds it stimulating, she'll let him mate.

This female doesn't,

and wipes his scent off as fast as he smears it on.

He has no time to waste, and moves on to look for another female.

Here's one.

This female likes his scent, and he mates.

Success.

But to make sure that she doesn't mate with any others,

he climbs back onto her and smears on more hormones.

Now other males will not find her receptive.

And he will be almost certain to pass on his genes.

At least some of the next generation will be his.

In the African rainforest, a particularly dangerous bug

has evolved a surprisingly balletic way to win his mate.

There are over 2,000 species of scorpion.

And while only 20 of them are dangerous to humans,

all of them are deadly to other bugs.

These Tanzanian red claws, like all scorpions, are mainly nocturnal.

Their mating rituals generally take place at night.

But their bodies fluoresce under ultraviolet light,

and that makes it possible for us to watch their most intimate behaviour.

When the female finds a male, their extraordinary ritual begins.

They dance.

He arouses her...

by caressing her mouth parts.

But while he tries to stimulate her, she is testing his strength.

She yields.

Now he is leading her.

Eventually, he deposits his sperm on the ground

and gently pulls her onto it.

He's proved his strength and agility,

and she has ensured the best possible father for her young.

Arthropods have many fascinating courtship rituals...

..from the dance of the scorpion...

..to the Goliath beetles' battle of strength...

..and the tarantulas' intimate embrace.

But, for some creatures, courtship is more violent.

And this happens in even the smallest worlds.

This dish contains a complete colony of tramp ants.

They're minute.

Each individual is less than the size of a grain of sand.

So, to see them properly, we have to use huge magnifications.

But they're worth watching, because the dominant male has

a really brutal way of ensuring that only he breeds.

200 times magnification reveals the intimate workings

of this tiny colony.

A few hundred ants, all at work.

The winged females are queens, and they're ready to mate.

And these two males are fighting for the right to mate with them.

The colony's current dominant male is the yellower of the two.

He must somehow drive all the other males out of the nest,

leaving him as the only male that can mate.

But he's not strong enough to kill the other males himself.

Instead, he gets other ants to do his dirty work.

He smears a rival male with a powerful scent.

This makes it smell like an invader.

The colony's sterile worker ants attack it on the dominant

male's behalf, slicing it in two.

In this colony, at least, violence pays.

On the forest floors of India, another insect is taking

a much gentler, but no less devious, approach to securing a mate.

These male tropical house crickets are chirruping by rubbing

their wings together in the hope of attracting females.

Their calls are so loud that the females can hear them

from 20 metres away.

This female has made her choice.

But the male has a trick to increase the chances

of his sperm fertilising her.

He will give her a present.

She sits on top of the male and tastes him

with her antennae to make sure she hasn't mated with him already.

He responds by producing a parcel of sperm, wrapped in a rich syrup.

As he leaves, the parcel sticks to the female's sex organs.

She eats the syrup...

..and his sperm remains attached to her sex organs.

This gift of food distracts the female

as fertilisation takes place...

..and makes her far less likely to go off searching for another mate.

The male's gift has ensured that he fathers her offspring.

Throughout the tropics, one insect has come to symbolise the extremes

that some animals will go to in order to mate.

Praying mantises are highly skilled predators...

..and they hunt by sight.

But their hearing is limited to just one sound.

They can detect bat sonar to avoid being eaten.

Praying mantises are so named

because of their pius-looking posture.

But these bugs are neither meek nor mild.

They are veracious predators.

They'll mostly eat locusts and crickets

but have been known to eat creatures far larger than themselves.

This male mantis, climbing up towards his potential mate,

can have little idea of the danger that he's in.

Perhaps put off by the unwelcome advances of the male,

or simply driven by hunger,

the female mantis begins to eat her suitor.

Holding his upper body in her left claw,

she starts to chew through his thorax...

..until the two halves of his body are only held

together by a thread of flesh.

Eventually, his head drops away.

Remarkably, this male isn't entirely dead.

He's begun to impregnate her.

The female has removed his head and, with it,

the brain cells that control his inhibitions,

but his abdomen has its own nerve cells.

Cells that control the act of copulation,

and they allow him to pass on his genes, even in the throws of death.

In reproductive terms, this male has succeeded.

But his death is a symbol of how strangely unfeeling

the arthropod world can be.

Every species of animal must reproduce.

If it didn't, it would become extinct.

Arthropods have developed many different ways of doing so,

some fantastic, some violent,

and their success has led them

to becoming one of the most abundant forms of animals on this planet.

Bugs will dance, fight

and even sacrifice their lives just to find a mate.

Courtship is key to their success.

But more important still is what happens next -

the arrival of offspring.

The birth of a new generation.

In the next programme, I'll meet the creatures that do without sex

altogether and produce millions of young in a single summer.

Watch the arrival of thousands of baby spiders...

..and look at perhaps the most remarkable

transformation in the animal kingdom...

The moment when the feeding machine that was a caterpillar

becomes the breeding machine that is an adult butterfly.