All language subtitles for David.Attenborough.Micro.Monsters.S01E04.Reproduction.2160p.NOW.WEB-DL.DDP5.1.H.265-RAWR_track3_[eng]

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 cast their webs.

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

Welcome to a strange
and dangerous world.

Every species of animal must
reproduce.

If it didn't it would go extinct.

Arthropods have developed many
ways of doing so.

From courtship and mating...

...to egg laying.

The hatching of larvae...

...to caring for the newly-born
young.

And some insects meet
the reproductive challenge

by splitting their life cycle
in two.

And all in order to produce
offspring

and ensure they get the best
possible start in life.

The arthropods' success in doing
so has lead them

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

In the woodlands of Madagascar
and parts of Southern Africa lives

a spider that has to rely on stealth
in order to mate and father young.

This is the male
golden orb web spider.

He hatched two months ago
and is now looking for a mate.

He's found a female's web
and he's lurking at its edge.

This is the female.

As spiders go, she's huge.

Her body alone is as long as your
thumb and her legs span some 15cm.

She's about 20 times
the size of the male.

Not only that,
she's a deadly predator...

...with a voracious appetite.

And all this makes mating a risky
business for the male.

The start of their courtship is
triggered by the insect

the female has already captured.

She is distracted by it,
so he seizes his opportunity.

He cautiously begins an approach...

He climbs very tentatively
onto her abdomen.

Now he's in position,
he deposits his sperm.

Success!

His alertness has saved him from
becoming the female's next meal.

He will only mate
once in his short life

and this is his reward.

He is father to the 400 or
so eggs in this egg sac.

A few weeks later the young
emerge from it.

The spiderlings are each no
bigger than a pinhead.

To begin with,

they stay close to the egg
sac from which they emerged.

They moult and then, after 30 days,
they start to disperse.

Golden orb web spiders
live for only a year.

Mating is the culmination
of their lives.

For some creatures though,
time is simply too short for mating,

so the females reproduce
without a male.

Spring is the season
when most arthropod eggs hatch.

But in colder climates,
spring arrives late

and the summer is short,

leaving little time to mate

and for the young to grow strong
enough to survive the coming winter.

Megabunus, a species of harvestmen,
has a way of dealing with that.

The female lives in Alpine forests

and spends the freezing winter
sheltered in the leaf litter.

She emerges in spring
and starts to hunt.

Her long legs help her to
clamber over the moss.

In fact,
her legs are so long, that she

has breathing holes in them
to supply them directly with oxygen.

But she must reproduce
if the species is to survive.

So she does so without mating.

She lays unfertilised eggs which
hatch into exact genetic

copies of herself -

clones.

She adapted her reproduction
to the harsh climate and

so sacrificed the genetic variation
that could've come with sex.

But other plant-eaters in gentler
climates use the same

technique to take advantage of the
glut of food that comes with spring.

Aphids also clone their offspring,
and what is more,

a female produces her young alive.

And she can do
so ten times a day or more.

Not only that, each of her offspring
will start producing

young of their own within days.

If the descendants of a single
female all survived,

they would, by the end of summer,
number 600 billion.

All of them identical clones.

But as the winter
approaches the aphids

change their way of reproducing.

They lay eggs.

Aphids cannot survive
the cold of the winter,

but the eggs are hardy
and will hatch next spring.

And then, once again,
the aphid population will explode.

The million or so species of
arthropod on our planet have matched

the way they reproduce to
suit the particular

environment in which they live.

Most of them lay eggs.

And some do
so in scarcely believable numbers.

Once such lives on a hedgehog.

Ixodes is a tick - a parasite.

The female is so well adapted to
life on a hedgehog that she

rarely lives anywhere else.

She has a limitless supply of food
immediately beside her -

blood.

She stays on the hedgehog
until she's ready to lay her eggs.

Then she lets go,
falls to the ground...

...and starts to deposit her
eggs in the undergrowth.

The eggs make up 50% of her
entire body weight.

She can lay around 1,500 of them

and it takes her up to 20 days
to lay them all.

Producing so many is her
way of ensuring that at least one or

two of her young will
find their own hedgehog host.

For those that do the cycle can
begin again.

By the time Ixodes has
produced them all,

her once plump body is deflated
and she dies.

Some insects, among them
butterflies, have developed

a way of growing that involves
a truly astonishing transformation.

This is a Heliconius butterfly.

And THIS is its offspring -

a caterpillar.

The two look as though they're
completely different creatures,

but of course, they're not.

The butterfly has
divided its life into two halves.

The first half, the caterpillar,

is devoted almost exclusively to
gathering food and growing.

And the second, the adult,

is devoted almost entirely to
reproduction.

Adult butterflies
feed on nectar which they locate

with their antennae,
taste through their feet

and collect with long,
tube-like mouthparts.

This sugar-rich food
fuels their search for a mate.

Once a male and female have found
one another, the male uses special

claspers at the end of his abdomen
to transfer his sperm to her.

Once fertilised,
the female Heliconius lays her

eggs on the leaves of the
passion flower plant.

Her young, the caterpillars,
are fussy eaters

and these leaves are almost
the only ones they will eat.

She lays around 50 eggs
and then her work is done.

About a week later
the caterpillars emerge.

They are little more than
eating machines

and they get down to work
immediately.

Some, over a month or two, can grow
to 40 times their original size.

They have protective spines to
ward off their predators,

but no reproductive organs.

Then, when they've grown enough,
their behaviour changes.

They stop eating and settle
in a suitable resting place.

Then their skins hardens to
form a shell.

This is a chrysalis.

If we could see inside we would
witness one of the most

extraordinary
changes in the animal kingdom...

...metamorphosis.

Some parts of the caterpillar
are transformed

and others disappear completely.

The caterpillar had a massive
gut for processing food,

that shrinks for nectar will be
easier to digest than

the leaves the caterpillar consume.

The mouth parts must change -
the adult needs not munching jaws,

but a tube-like tongue.

And the caterpillar's simple
eyes are also transformed.

Searching for a mate needs better
eyesight than finding leaves.

Antennae sprout form its head.

It will use them to sniff out
the scent of a female or a flower.

And finally, its wings,
their shape and colour will

warn off predators and enable it
to find and select a suitable mate.

An adult Heliconius butterfly
emerges after

eight days of transformation.

Its delicate wings are crumpled
and wet.

It stretches them
by pumping blood along their veins

and then waits for them
to dry before attempting to fly.

From this point on its body will
not grow or change...

It will live for just a month or two

and feed just enough to keep
itself going.

This body is purely for mating.

A male's antennae can detect
females' scent from more than

a kilometre away.

And he's off to find a female.

Success for this butterfly is
reproduction,

as it is for all species.

And that need has shaped the bodies,
the behaviour,

the entire life cycle of all
arthropods, and produced

the dazzling range of forms that we
see around the world today.

Every generation must
reproduce itself,

if it does not a species
will disappear.

From the cunning,
tiny make golden orb web spider...

...to the amazingly fertile aphids
that clone themselves to make

the most of summer.

And the tick that leaves its
hedgehog host to lay its eggs.

The arthropods have evolved
reproductive strategies

that are surely among the most
fascinating,

almost unbelievable
stories, in the natural world.

In our next programme,

I'll be looking at what happens
after reproduction.

Over 400 million years ago some
early arthropods began to

care for their young
and to live in groups.

And for these too, life was
about more than just staying alive,

it was about giving the next
generation the best

chance of survival.

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