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Our planet is the greatest
living puzzle in the universe.

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A collection of worlds

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within worlds.

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Each one a network of relationships

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and connections

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between all their living parts

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leading to the diverse
and complex world we live in.

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And at the heart
of many of these worlds

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is a very special group of animals.

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The insects and their close
relatives,

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the arachnids and crustaceans,

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classed together as the arthropods.

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Together, they account for 80%
of all animal species on our planet.

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In these three specials,

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we're going to explore
the connections and relationships

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that they have with us,
our planet

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and with each other.

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Ultimately to understand
how this group

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hold the key to life itself

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inside nature's microworlds.

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Humans evolved around
200,000 years ago

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into a world that was dominated
by the arthropods.

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In that time, we've learnt
to live alongside each other,

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taking the benefits and putting up
with some of the annoyances.

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But do we understand
what life would be like

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without this group of animals?

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How many of us really know

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how intricately linked
our lives have become

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that, without the arthropods,
life as we know it would not exist?

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Some even question

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if survival of the human race
would be possible at all.

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But how can this be?

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What have the arthropods
ever done for us?

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The ways they affect human life
are diverse and far reaching

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and to really understand
the importance of this influence,

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we need to unpick the relationships,

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both good and bad,

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that we have with the arthropods.

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One of the most intriguing ways
they influence us

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occurs in the forests of Kenya.

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These driver ants
are searching for food.

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They're efficient hunters

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moving through the forest
like a tidal wave.

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They'll eat any living animal
in their path.

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Colonies can number up to 22 million

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and it's said that even elephants
will turn and flee

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when they see them coming.

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These lethal predators
are actually totally blind.

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They rely on touch, smell and
chemical signals to find their way.

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The soldiers flank the raiding
columns of workers

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with immense jaws raised.

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Anything that can't outrun them

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risks becoming their prey.

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This is perhaps how most of us
view arthropods -

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creepy crawlies that are
nothing more than a problem.

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But their presence is actually

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a real asset for these villagers.

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The ants can capture up to
100,000 insects in a single raid,

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providing invaluable pest control
for the farmers.

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Pests inside homes and
in surrounding fields are removed,

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dismembered and devoured.

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In fact, the whole place is given
a five-star ant clean-up.

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Thanks to their highly effective
cleaning raids,

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these ants play a key role

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in the lives of the locals.

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But arthropods can provide us

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with something even more important
than a service.

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They can provide us with one
of the essential elements of life.

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900 miles south of Kenya

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lies Lake Malawi.

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Beneath the water,
something's stirring.

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Trillions and trillions of lake fly
larvae are getting ready to emerge.

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After many months buried
in the sediment on the lake floor,

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they'll take to the air to mate.

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Towers of mating flies stretch
hundreds of metres into the air.

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Like smoke, they rise

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from the surface of the lake.

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The towers of flies are swept
by the wind towards the shore

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and towards human habitation.

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Here, they cloak vegetation

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and engulf whole forests
and villages in their path.

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This may seem like an annoyance,

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but, actually, these flies
present great opportunity.

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Villagers sweep baskets
through the air to catch the flies.

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The biomass of these flies
is equivalent to huge herds of game

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that roam the surrounding plains,

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but they're far easier to catch.

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The flies are then made into patties

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and fried in hot oil.

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Each patty contains
half a million flies

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and has seven times more protein
than the average beef burger.

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For people who have little
protein in their diet,

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this can be a lifesaver.

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It may feel a long way from our idea
of a perfect meal,

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but the importance
of eating arthropods

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shouldn't be underestimated.

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Over 11 million tonnes
of crustaceans

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are consumed by humans every year.

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In Botswana, the mopane worm
collection industry

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is worth millions of pounds
each year.

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For 2.5 billion people worldwide,

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insects are a vital source of food.

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More than a thousand insect species

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form a regular part
of the human diet.

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Rich in vitamins,
protein and minerals.

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It's mainly in the West

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that people are uncomfortable
with the idea of eating insects.

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But the United Nations believe

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that eating insects
instead of mammal meat

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may provide a solution
to stamping out famine

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and reducing climate change.

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The raising of livestock
such as cows, pigs and sheep

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occupies two thirds
of the world's farmland

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and generates 20%
of all greenhouse gases.

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With the human population
projected to reach nine billion

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in just 40 years' time,

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the consumption of arthropods

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could provide a healthy Earth-saving
measure.

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So, in the future,
arthropods have the potential

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to address our global food crisis.

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That's no small claim.

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But they've also played
an enormous role in shaping our past

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to such an extent that human life,
as we know it,

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would not exist if it weren't
for this next arthropod product.

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It all started with a cocoon

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and a beautiful piece of cloth.

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China - home to a billion people

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and a very special arthropod.

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This is a silk worm caterpillar.

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They eat only mulberry leaves.

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And, after 50 days of feeding,

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they'll be 10,000 times heavier
and ready to transform.

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25% of their body mass
is made up of silk glands.

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They spin a cocoon
using a single thread

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which can be over 900 metres
in length.

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And it's this silk that forms
the basis of an industry

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that's shaped our history

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and today, has a commercial value

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of up to £300 million.

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The cocoons are boiled and precious
silken threads begin to unwind.

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But this arthropod product is not
only responsible for human clothing.

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It's shaped our culture
for over a thousand years.

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The transport of silk
from Asia towards Europe

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led to the establishment of
the famed Silk Road around 200 BC.

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This 4,000-mile trade route

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forged relationships between
different and diverse cultures.

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And was pivotal in the development
of the civilisations

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in China, India, Europe and Arabia.

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So silk has shaped human culture
and distribution,

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but there's another arthropod
product that's valued so highly

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humans will risk their life
trying to collect it.

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The Himalayas, in Nepal.

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These men are climbing 400 metres
up sheer cliffs

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to steal from giant honey bees.

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They're the largest honey bee
in the world

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and their stings are notoriously
painful.

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So what could make men
risk their lives in this way?

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Honey!

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These bees, like honey bees
the world over,

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take nectar from the surrounding
flowers

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and spit it into the cells
in the comb.

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Enzymes in their saliva
break down the sugars

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and water evaporates
until the condensed honey remains.

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This honey will be the colonies'
sole source of food

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during the colder winter months

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and they'll give up their lives
to protect it.

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So the honey gatherers will not only
have to deal with perilous heights,

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but also with angry bees.

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When the men finally reach the comb,

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they must manoeuvre sticks

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to work free a section of honey.

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With little protection
against the stings,

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they must work quickly before
being overcome by the bees venom.

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The honeycomb is dropped
into a suspended basket

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and then lowered to the ground.

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They leave a large section
of the comb intact

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so the colony can rebuild
its honey supplies.

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Job complete, the men can descend
to enjoy their hard-won prize.

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Honey's made up
of 80% natural sugars

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and so, provides a vital
energy-rich food source

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for these mountain dwellers.

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So prized is this product

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that the farming of arthropods
for their honey has now gone global.

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Around 1.2 million tonnes of honey
is produced worldwide each year.

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When you think that one little
bee in its entire lifetime

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produces only about
a spoonful of honey,

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that's a humbling amount of work

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from our arthropod friends.

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But honey isn't the only product
that bees provide us with.

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Bees and their relatives

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have a much more far reaching
and significant effect on us humans.

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Without which, it's questionable
if humans would survive at all.

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And to see what this is,

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we must examine a wonderful process
happening all around us

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and responsible for shaping
the world we live in.

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The coastal cliffs of Sardinia,

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in the Mediterranean,

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are home to an unusual plant.

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The dead horse arum.

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It looks like a dead rotting animal

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and has a smell to match.

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This canny flower even raises
its temperature

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by as much as 20 degrees
above the surrounding vegetation

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to complete its disguise.

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The smell is taken by the wind

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and it's not long
before the arum is noticed.

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These flies are hoping
they've found a carcass

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on which to lay their eggs,

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but, instead, they become trapped.

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Inside the flower,

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they brush against the female stigma

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releasing any pollen
they're already carrying.

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This flower is now pollinated.

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Spines prevent the flies' escape
and they're trapped.

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Overnight, when the flies
are inactive,

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the spines wither and the male
pollen above them ripens

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ensuring that, in the morning,

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each exiting fly is coated with
pollen to take to the next flower.

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This flower has invested everything

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in the process of cross-pollination.

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It's modified its appearance,

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its smell, its temperature

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and its internal barriers,

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all to ensure the transfer
of pollen grains

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from one plant to another.

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And it's this process of pollination

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that's the next key

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to why the arthropods are pivotal
to human success

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and to our very own food chain.

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As much as 35% of all human food

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is dependent on pollination
by arthropods.

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Across the world, the value of crops
pollinated by insects

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is over £120 billion a year.

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Without them, we wouldn't have
apples, almonds, cherries, oranges,

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tomatoes or squash
on our supermarket shelves.

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84% of crop species grown in Europe

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still depend on insect pollination.

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Without insects,
our crops would flounder,

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supermarket stocks would plummet

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and life on Earth
would irreversibly suffer.

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But to really understand our
relationship with the arthropods,

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we need to examine their negative
effects as well as the positive.

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The deserts of West Africa.

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Moisture in the soil
and increased temperatures

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provide the triggers
for a mass hatching.

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Eggs that may have lain dormant
for 20 years hatch

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and flightless locusts,
called hoppers emerge.

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These hoppers follow the smell
of freshly sprouting grass.

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After about 20 days of feasting,

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they transform into winged adults
and form a swarm.

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A swarm can cover an area
of 1,000 square miles

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and can literally blot out the sun.

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They eat their own body weight
in food each day.

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En masse, they can get through
200,000 tonnes of crops,

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00:18:34,000 --> 00:18:36,400
enough to feed
half a billion people.

256
00:18:46,320 --> 00:18:50,320
Many arthropods have the potential
to reach biblical proportions.

257
00:19:02,440 --> 00:19:06,280
Their ability to reproduce quickly
and prolifically

258
00:19:06,280 --> 00:19:08,880
means their numbers,
left unregulated,

259
00:19:08,880 --> 00:19:10,480
can snowball out of control.

260
00:19:14,440 --> 00:19:17,480
For us humans, that can present
a real problem.

261
00:19:23,080 --> 00:19:27,240
And there's a parasite that's
utilised this breeding success

262
00:19:27,240 --> 00:19:31,240
and today, it's the biggest cause
of human fatality on our planet.

263
00:19:40,960 --> 00:19:43,920
It kills 3,000 people every day

264
00:19:43,920 --> 00:19:46,800
and without arthropods,
it wouldn't exist.

265
00:19:48,400 --> 00:19:49,800
Throughout history,

266
00:19:49,800 --> 00:19:53,720
this relentless killer has claimed
more victims than any other disease.

267
00:19:55,840 --> 00:19:59,360
It's killed more people than
both the world wars put together

268
00:19:59,360 --> 00:20:02,640
and at least 40% of the world's
population are at risk.

269
00:20:06,720 --> 00:20:09,320
The disease is carried
by the Anopheles mosquito

270
00:20:09,320 --> 00:20:11,160
and it's called malaria.

271
00:20:13,920 --> 00:20:15,640
But, really, this mosquito

272
00:20:15,640 --> 00:20:17,960
is just a pawn in a parasite's game.

273
00:20:21,040 --> 00:20:23,760
The parasite lives
by eating the red blood cells

274
00:20:23,760 --> 00:20:25,240
of the victim it attacks.

275
00:20:27,680 --> 00:20:30,120
When a mosquito bites
an infected person,

276
00:20:30,120 --> 00:20:33,520
it sucks up the blood containing
the parasite into its gut.

277
00:20:35,240 --> 00:20:37,200
The parasite multiplies...

278
00:20:40,240 --> 00:20:43,040
..then, burrows into the mosquito's
saliva gland...

279
00:20:45,720 --> 00:20:47,480
..where it's squirted into the blood

280
00:20:47,480 --> 00:20:49,240
of the mosquito's next victim.

281
00:20:53,320 --> 00:20:55,040
And so, the cycle continues.

282
00:20:57,280 --> 00:20:59,320
But can we really blame
the mosquito?

283
00:21:02,080 --> 00:21:04,600
It gains nothing
from carrying the parasite.

284
00:21:10,560 --> 00:21:12,200
And, ironically, mosquitoes,

285
00:21:12,200 --> 00:21:13,800
along with other arthropods,

286
00:21:13,800 --> 00:21:17,400
might be the ultimate solution
to this deadly disease

287
00:21:17,400 --> 00:21:19,640
in their ability
to regulate each other.

288
00:21:28,960 --> 00:21:31,080
An example of this is played out

289
00:21:31,080 --> 00:21:33,080
in a field in the South Downs.

290
00:21:37,520 --> 00:21:41,440
These aphids are doing
what aphids do best -

291
00:21:41,440 --> 00:21:43,120
multiplying.

292
00:21:47,040 --> 00:21:48,600
They're breeding machines

293
00:21:48,600 --> 00:21:50,280
and, by the end of a season,

294
00:21:50,280 --> 00:21:53,720
a single aphid can have produced
over a billion descendants.

295
00:22:05,360 --> 00:22:08,520
Each aphid uses their specialised
mouth parts

296
00:22:08,520 --> 00:22:10,840
to suck out the plants' juices.

297
00:22:10,840 --> 00:22:14,560
Left uncontrolled, they can
devastate a whole field of crops.

298
00:22:17,920 --> 00:22:20,680
Luckily for farmers and gardeners,

299
00:22:20,680 --> 00:22:23,200
there's a crack team of predators
on standby.

300
00:22:26,160 --> 00:22:29,360
Firstly, the colourful
but ferocious ladybird.

301
00:22:33,880 --> 00:22:37,720
One ladybird can eat over
5,000 aphids in a lifetime.

302
00:22:40,120 --> 00:22:42,640
But working alone,
they'd have their work cut out

303
00:22:42,640 --> 00:22:45,440
to keep up with the prolific
breeding of the aphids.

304
00:22:46,520 --> 00:22:48,480
Luckily, they've got backup.

305
00:22:50,360 --> 00:22:54,200
Money spiders parachute in from
surrounding fences and hedgerows.

306
00:22:57,680 --> 00:23:01,160
The spiders spin delicate
but lethal orb webs

307
00:23:01,160 --> 00:23:03,320
and wait for their prey to arrive.

308
00:23:08,800 --> 00:23:11,520
When the bumbling ladybird
has had her fill,

309
00:23:11,520 --> 00:23:13,840
her movements dislodge
further aphids

310
00:23:13,840 --> 00:23:16,120
that drop into the silken traps
below.

311
00:23:17,560 --> 00:23:20,080
This natural balance
of predators and prey

312
00:23:20,080 --> 00:23:22,880
may seem only relevant
to gardeners and farmers,

313
00:23:22,880 --> 00:23:26,920
but the global importance
of this natural biological control

314
00:23:26,920 --> 00:23:28,600
is not to be underestimated.

315
00:23:31,960 --> 00:23:35,040
Pest control services
provided by insects were valued

316
00:23:35,040 --> 00:23:37,840
at over 60 billion dollars a year,
in the USA alone.

317
00:23:40,440 --> 00:23:43,200
This is a service
we really can't afford to lose.

318
00:23:50,040 --> 00:23:53,880
And the arthropod regulators
could potentially provide some hope

319
00:23:53,880 --> 00:23:57,240
against the worst disease
the human race has ever faced.

320
00:24:01,440 --> 00:24:04,360
There are plans for
a non-malaria-carrying mosquito

321
00:24:04,360 --> 00:24:08,080
to be released to outcompete
the deadly malaria-carrying ones.

322
00:24:11,760 --> 00:24:16,160
So we've seen how arthropods
provide us with food and products.

323
00:24:16,160 --> 00:24:19,840
How they've shaped
our distribution and culture.

324
00:24:19,840 --> 00:24:23,440
We've seen how pivotal they are
to our own food chain

325
00:24:23,440 --> 00:24:28,480
and how their presence can regulate
pests and even fatal diseases.

326
00:24:30,440 --> 00:24:33,720
But there's one final key
to how they influence our lives...

327
00:24:35,960 --> 00:24:38,080
..one final offering
from the arthropods

328
00:24:38,080 --> 00:24:41,080
that could shape the way we exist
and operate in years to come.

329
00:24:53,360 --> 00:24:54,880
In this vast colony,

330
00:24:54,880 --> 00:24:59,080
every army ant appears
to be following a master plan,

331
00:24:59,080 --> 00:25:01,720
like tiny cogs in a huge machine.

332
00:25:06,600 --> 00:25:10,360
They allocate resources depending
on environmental conditions.

333
00:25:13,280 --> 00:25:15,720
If a rich food source is found,

334
00:25:15,720 --> 00:25:18,200
workers will appear
to deal with the bounty.

335
00:25:25,800 --> 00:25:28,680
They build organised highways
with no congestion.

336
00:25:32,080 --> 00:25:36,280
They construct shelter
and a place to rear their young

337
00:25:36,280 --> 00:25:38,080
using their own bodies.

338
00:25:39,800 --> 00:25:41,960
They stage foraging raids

339
00:25:41,960 --> 00:25:44,760
and vacate an area of forest
when food sources dwindle.

340
00:25:47,440 --> 00:25:50,600
They're efficient,
responsive and smart.

341
00:25:50,600 --> 00:25:53,480
Everything our human organisations
strive to be.

342
00:25:55,880 --> 00:25:57,800
But this colony doesn't function

343
00:25:57,800 --> 00:26:00,520
like any organisation we humans
are familiar with.

344
00:26:03,720 --> 00:26:06,760
There's no central control,
no figure of authority.

345
00:26:06,760 --> 00:26:09,440
The queen ant may have
her lofty title,

346
00:26:09,440 --> 00:26:11,560
but plays no role in coordination.

347
00:26:16,480 --> 00:26:20,360
And we're just starting to learn
how such efficiency is achieved.

348
00:26:27,480 --> 00:26:31,680
Haulage companies and airports
are learning to operate like ants.

349
00:26:35,240 --> 00:26:38,280
Abandoning pre-determined
master plans

350
00:26:38,280 --> 00:26:40,440
and instead focusing on smaller,

351
00:26:40,440 --> 00:26:41,680
smarter decisions.

352
00:26:43,360 --> 00:26:45,840
And it's not just the ants
that we're learning from.

353
00:26:48,440 --> 00:26:51,720
Bees are teaching us how to build
honeycomb-style structures

354
00:26:51,720 --> 00:26:56,160
providing maximum strength
while using minimal materials.

355
00:26:56,160 --> 00:26:59,760
Spiders are helping us design
crawling robots

356
00:26:59,760 --> 00:27:02,000
for inspecting ship hulls

357
00:27:02,000 --> 00:27:03,480
and nuclear reactors.

358
00:27:06,080 --> 00:27:08,480
Butterflies hold the key
in their wings

359
00:27:08,480 --> 00:27:12,240
to harnessing the sun's energy
more efficiently than ever before.

360
00:27:15,360 --> 00:27:19,280
And termites, with their unpowered
air conditioning towers,

361
00:27:19,280 --> 00:27:20,880
are inspiring architects.

362
00:27:25,320 --> 00:27:28,720
It seems that arthropods
really do have a lot to teach us.

363
00:27:32,520 --> 00:27:35,720
Arthropods have been pivotal
in shaping our culture

364
00:27:35,720 --> 00:27:37,440
and distribution.

365
00:27:40,720 --> 00:27:44,680
Without them, our food chains
would collapse

366
00:27:44,680 --> 00:27:47,920
and pests would multiply
beyond control.

367
00:27:59,320 --> 00:28:01,880
We humans would do well to remember

368
00:28:01,880 --> 00:28:05,240
that arthropods could survive
perfectly well without us.

369
00:28:07,320 --> 00:28:13,240
But life as we know it
could not continue without them.

370
00:28:53,160 --> 00:28:58,200
Our planet is the greatest
living puzzle in the universe.

371
00:28:58,200 --> 00:29:01,240
A collection of worlds
within worlds.

372
00:29:01,240 --> 00:29:05,040
Each one a network of relationships
and connections

373
00:29:05,040 --> 00:29:07,560
between all their living parts,

374
00:29:07,560 --> 00:29:11,480
leading to the diverse
and complex world we live in.

375
00:29:14,000 --> 00:29:15,760
And at the heart
of many of these worlds

376
00:29:15,760 --> 00:29:17,960
is a very special group of animals...

377
00:29:19,280 --> 00:29:23,960
..the insects and their
close relatives, the arachnids

378
00:29:23,960 --> 00:29:28,080
and crustaceans -
classed together as the arthropods.

379
00:29:29,840 --> 00:29:33,880
Together they account for 80%
of all animal species on our planet.

380
00:29:35,280 --> 00:29:38,520
In these three specials, we're going
to explore the connections

381
00:29:38,520 --> 00:29:41,720
and relationships
that they have with us,

382
00:29:41,720 --> 00:29:43,280
our planet...

383
00:29:44,840 --> 00:29:47,560
..and with each other.

384
00:29:47,560 --> 00:29:50,520
Ultimately to understand
how this group

385
00:29:50,520 --> 00:29:56,600
hold the key to life itself inside
nature's microworlds.

386
00:30:03,720 --> 00:30:05,280
At least one species of Arthropod

387
00:30:05,280 --> 00:30:08,200
can be found
in every microworld on Earth.

388
00:30:09,400 --> 00:30:13,280
From baking deserts
and lush rainforests...

389
00:30:14,960 --> 00:30:16,600
..to open oceans...

390
00:30:18,560 --> 00:30:21,200
..and dark caves.

391
00:30:26,080 --> 00:30:29,240
And although seemingly insignificant
in size...

392
00:30:32,040 --> 00:30:35,400
..the influence they have
on our planet is immense.

393
00:30:44,040 --> 00:30:48,360
But to understand how arthropods
have come to play such a vital role,

394
00:30:48,360 --> 00:30:52,160
we must explore
a wide variety of ecosystems.

395
00:30:56,640 --> 00:30:58,800
And we'll investigate
the arthropods'

396
00:30:58,800 --> 00:31:01,280
greatest influence of all.

397
00:31:01,280 --> 00:31:04,600
Could they be responsible
for the richness and diversity

398
00:31:04,600 --> 00:31:06,560
of nature's many microworlds?

399
00:31:13,720 --> 00:31:15,000
There's one microworld

400
00:31:15,000 --> 00:31:18,680
where the impact of a single species
of arthropod is evident -

401
00:31:18,680 --> 00:31:21,520
the Argentinean Pampas Grassland.

402
00:31:23,480 --> 00:31:28,640
A landscape that's been created
almost solely by one tiny creature.

403
00:31:31,800 --> 00:31:33,200
Grass cutter ants.

404
00:31:35,000 --> 00:31:37,720
These insects are only
one-and-a-half centimetres long

405
00:31:37,720 --> 00:31:41,160
and yet they achieve something
few animals are capable of.

406
00:31:43,640 --> 00:31:45,240
Through their activities,

407
00:31:45,240 --> 00:31:47,560
they have completely altered
their own environment.

408
00:31:50,400 --> 00:31:53,240
Grass cutter ants are the farmers
of these grasslands

409
00:31:53,240 --> 00:31:55,880
and like farmers,
they shape the vegetation.

410
00:31:59,640 --> 00:32:02,160
Each year,
a single colony will harvest

411
00:32:02,160 --> 00:32:04,880
over half a tonne of grass cuttings.

412
00:32:08,680 --> 00:32:11,680
Surprisingly,
these ants don't actually eat grass,

413
00:32:11,680 --> 00:32:15,320
but they have found a way
to cultivate their crops

414
00:32:15,320 --> 00:32:17,160
and this happens underground.

415
00:32:21,280 --> 00:32:24,320
Their nests dominate
the subterranean environment

416
00:32:24,320 --> 00:32:27,040
with tunnels extending
over seven metres deep.

417
00:32:28,280 --> 00:32:30,000
Here they share their chambers

418
00:32:30,000 --> 00:32:33,560
with a special fungus
that's found nowhere else on Earth.

419
00:32:35,760 --> 00:32:38,840
And this fungus can digest grass.

420
00:32:40,400 --> 00:32:43,000
The ants feed their grass harvest
to the fungus

421
00:32:43,000 --> 00:32:46,800
and in return
the fungus produces edible gardens.

422
00:32:49,560 --> 00:32:51,960
These fungus gardens
are prolific enough

423
00:32:51,960 --> 00:32:54,040
to feed the whole colony of ants.

424
00:32:54,040 --> 00:32:56,160
All 5 million of them!

425
00:32:58,400 --> 00:33:00,680
But their impact does not end there.

426
00:33:03,000 --> 00:33:04,880
They also alter the landscape.

427
00:33:06,120 --> 00:33:08,960
The fungus releases carbon dioxide -

428
00:33:08,960 --> 00:33:11,560
lethal in large concentrations.

429
00:33:11,560 --> 00:33:14,840
But the ants have a clever way
of combating its build up.

430
00:33:16,760 --> 00:33:20,760
They construct massive towers
that help draw fresh air in

431
00:33:20,760 --> 00:33:22,640
and suck stale air out,

432
00:33:22,640 --> 00:33:25,240
effectively acting like
air conditioners.

433
00:33:27,080 --> 00:33:28,520
These grass cutter ants,

434
00:33:28,520 --> 00:33:31,160
with their incredible building
and farming skills,

435
00:33:31,160 --> 00:33:34,120
have completely shaped
this microworld.

436
00:33:34,120 --> 00:33:38,040
An ecosystem which, without the ants,
would not even exist.

437
00:33:41,520 --> 00:33:43,720
The arthropods' domination
of an environment

438
00:33:43,720 --> 00:33:45,640
is not always so complete

439
00:33:45,640 --> 00:33:48,200
but it can have
just as big an impact.

440
00:33:52,080 --> 00:33:55,120
In the most expansive ecosystem
on our planet,

441
00:33:55,120 --> 00:33:58,680
an arthropod plays such a key role
that, without it,

442
00:33:58,680 --> 00:34:02,960
the largest animal that has
EVER lived could not exist.

443
00:34:05,440 --> 00:34:09,600
Life within the ocean evolved 3
billion years prior to life on land.

444
00:34:12,840 --> 00:34:17,560
And today it's the home of 230,000
marine animal species.

445
00:34:21,520 --> 00:34:23,560
Arguably
the most important of these,

446
00:34:23,560 --> 00:34:25,080
the ones that are the key

447
00:34:25,080 --> 00:34:28,320
to this whole interconnected
oceanic ecosystem are...

448
00:34:30,320 --> 00:34:31,440
..the krill.

449
00:34:35,680 --> 00:34:39,200
Found across the world's oceans,
from the tropics to the poles,

450
00:34:39,200 --> 00:34:41,840
these arthropods fuel the ocean's
food chain.

451
00:34:44,400 --> 00:34:47,360
The reason they're so vital
to sustaining life in the oceans

452
00:34:47,360 --> 00:34:51,040
is their ability to consume
phytoplankton on a massive scale.

453
00:34:54,040 --> 00:34:56,320
Phytoplankton
are microscopic organisms -

454
00:34:56,320 --> 00:34:58,520
the sea's equivalent of grass.

455
00:34:58,520 --> 00:35:02,880
So vast in number,
their blooms can be seen from space.

456
00:35:05,280 --> 00:35:09,880
And krill are the ocean's
biggest consumer of phytoplankton.

457
00:35:12,800 --> 00:35:15,120
Just one species,
the Antarctic Krill,

458
00:35:15,120 --> 00:35:20,920
has a combined mass
of 379 million tonnes.

459
00:35:20,920 --> 00:35:23,240
That's over 90 million tonnes
heavier

460
00:35:23,240 --> 00:35:25,320
than the biomass
of the whole human race.

461
00:35:27,400 --> 00:35:30,600
Few large animals can feed
on the ocean's phytoplankton

462
00:35:30,600 --> 00:35:32,200
but they can feed on krill.

463
00:35:33,560 --> 00:35:36,080
So these tiny arthropods
are a critical link

464
00:35:36,080 --> 00:35:38,320
at the bottom of the ocean's
food chain.

465
00:35:40,200 --> 00:35:43,120
The krill feed the fish,
which feed bigger fish,

466
00:35:43,120 --> 00:35:45,600
which feed the birds and seals,

467
00:35:45,600 --> 00:35:47,880
and so the food chain continues.

468
00:35:49,880 --> 00:35:53,720
But sometimes the number of links
in the chain is remarkably small.

469
00:35:57,400 --> 00:35:58,400
The blue whale.

470
00:35:59,880 --> 00:36:02,400
The biggest animal
that's ever lived on the planet

471
00:36:02,400 --> 00:36:04,920
has short-circuited
the ocean's food chain

472
00:36:04,920 --> 00:36:06,960
and gone straight for the krill.

473
00:36:09,800 --> 00:36:12,720
Rather than teeth,
these ocean giants are equipped

474
00:36:12,720 --> 00:36:15,200
with a fine mesh of bristles,
called baleen,

475
00:36:15,200 --> 00:36:19,560
which allow each whale to filter out
up to 40 million krill a day.

476
00:36:26,640 --> 00:36:31,840
Without these tiny arthropods, the
blue whale may never have evolved.

477
00:36:36,240 --> 00:36:41,000
Arthropods play a pivotal role
in the underwater web of life

478
00:36:41,000 --> 00:36:44,120
but their influence
isn't just confined to the sea.

479
00:36:49,440 --> 00:36:52,840
On dry land, arthropods are also
the key food source

480
00:36:52,840 --> 00:36:55,240
for a whole host of other animals.

481
00:36:57,800 --> 00:36:59,400
Birds...

482
00:36:59,400 --> 00:37:01,600
reptiles...

483
00:37:01,600 --> 00:37:03,600
amphibians...

484
00:37:03,600 --> 00:37:05,120
and mammals.

485
00:37:07,800 --> 00:37:10,840
Like the blue whales,
there are also land-based animals

486
00:37:10,840 --> 00:37:14,000
that have special adaptations
for feeding on arthropods,

487
00:37:14,000 --> 00:37:17,640
like the pangolin
with its powerful digging claws.

488
00:37:22,440 --> 00:37:26,320
And the giant anteater
that has a 60cm long tongue,

489
00:37:26,320 --> 00:37:29,120
perfect for reaching into
ant and termite mounds.

490
00:37:36,200 --> 00:37:38,960
But there's an even more surprising
group of predators

491
00:37:38,960 --> 00:37:41,800
that rely on arthropods
for their food.

492
00:37:41,800 --> 00:37:45,880
And they don't even belong
to the animal kingdom.

493
00:37:45,880 --> 00:37:49,840
One species can be found
in the boglands of Scotland.

494
00:37:49,840 --> 00:37:53,440
The soil here is waterlogged
and lacking in vital nutrients,

495
00:37:53,440 --> 00:37:54,800
especially nitrogen.

496
00:37:56,440 --> 00:38:00,000
Under such conditions
few plants can grow

497
00:38:00,000 --> 00:38:02,120
but thanks to the presence
of arthropods,

498
00:38:02,120 --> 00:38:04,200
one species has found a way.

499
00:38:05,760 --> 00:38:09,280
This strange-looking plant
is the sundew -

500
00:38:09,280 --> 00:38:13,040
so named because of the dew-like
droplets on its leaves -

501
00:38:13,040 --> 00:38:15,120
but they're also extremely sticky.

502
00:38:19,560 --> 00:38:22,400
Their sweet smell
attracts many insects.

503
00:38:24,120 --> 00:38:26,720
As mosquitoes emerge
from the boggy water,

504
00:38:26,720 --> 00:38:29,120
they're drawn straight into
a sticky trap.

505
00:38:34,560 --> 00:38:38,240
Sensitive to touch, the tentacles
quickly wrap around the prey.

506
00:38:42,480 --> 00:38:45,200
Eventually, the insect dies
in the sticky fluid.

507
00:38:46,400 --> 00:38:50,320
With the help of enzymes,
its body is absorbed by the sundew.

508
00:38:53,440 --> 00:38:57,120
Without insects,
this plant would not survive.

509
00:38:57,120 --> 00:39:01,640
And without arthropods, many of our
planet's food chains would collapse.

510
00:39:03,680 --> 00:39:06,320
While the arthropods' role
as a food source

511
00:39:06,320 --> 00:39:08,920
is crucial to the survival of
millions of animals

512
00:39:08,920 --> 00:39:10,360
and even some plants,

513
00:39:10,360 --> 00:39:13,640
it's only a part of the giant jigsaw

514
00:39:13,640 --> 00:39:16,240
that makes our planet's
ecosystems tick.

515
00:39:23,000 --> 00:39:26,080
Nutrients form
the building blocks of life.

516
00:39:26,080 --> 00:39:28,480
So, for a microworld
to maintain its balance,

517
00:39:28,480 --> 00:39:31,480
it's vital that these nutrients
aren't wasted.

518
00:39:34,120 --> 00:39:36,440
This is where our next team
of arthropods

519
00:39:36,440 --> 00:39:39,600
play a critical role
as the recyclers.

520
00:39:43,080 --> 00:39:45,200
Within the rainforests of Borneo,

521
00:39:45,200 --> 00:39:49,560
a giant cave is home to a staggering
3 million wrinkle-lipped bats.

522
00:39:52,200 --> 00:39:55,480
With over 37 tonnes of insects
consumed every night,

523
00:39:55,480 --> 00:39:58,280
a huge mound of bat droppings
builds up.

524
00:40:00,520 --> 00:40:02,160
But this waste isn't wasted.

525
00:40:03,200 --> 00:40:05,240
Reaching up to 100 metres in height,

526
00:40:05,240 --> 00:40:09,920
this nutrient-rich mound fuels
a seething mass of cockroaches.

527
00:40:11,960 --> 00:40:15,760
One of the densest concentrations
of cockroaches in the world.

528
00:40:20,480 --> 00:40:23,920
Working with bacteria and fungi,
they break down the faeces.

529
00:40:27,800 --> 00:40:31,080
This is how they keep
this giant mound under control

530
00:40:31,080 --> 00:40:34,880
and keep the nutrients moving around
this tightly connected microworld.

531
00:40:38,920 --> 00:40:42,400
It's the recyclers that hold the key
to this cave's ecosystem.

532
00:40:46,200 --> 00:40:49,480
But their influence is perhaps
even greater 5,000 miles away,

533
00:40:49,480 --> 00:40:50,880
on the plains of Africa.

534
00:40:53,480 --> 00:40:55,400
This is the Serengeti...

535
00:40:58,560 --> 00:40:59,960
..home to the big five...

536
00:41:08,080 --> 00:41:09,480
..and the dung beetles.

537
00:41:17,560 --> 00:41:21,440
Using their remarkable sense of
smell, they hone in on their target.

538
00:41:23,400 --> 00:41:27,280
True to their name, dung beetles
are the masters of recycling dung.

539
00:41:29,280 --> 00:41:31,320
They don't need to eat or drink
anything else,

540
00:41:31,320 --> 00:41:34,600
as dung provides all the moisture
and nutrients they need.

541
00:41:40,600 --> 00:41:43,600
As the beetles roll off
and bury their own food balls,

542
00:41:43,600 --> 00:41:45,960
the dung patch quickly vanishes.

543
00:41:49,480 --> 00:41:52,880
But for these beetles, dung isn't
just a good source of food.

544
00:41:54,240 --> 00:41:58,560
This male is building a giant brood
ball, to help him entice a female.

545
00:42:09,320 --> 00:42:10,760
Mission accomplished!

546
00:42:16,680 --> 00:42:20,280
And now the female has
the perfect place to lay her eggs.

547
00:42:23,400 --> 00:42:26,640
While the beetles' circle of life
is centred around dung,

548
00:42:26,640 --> 00:42:31,320
the grasslands' entire ecosystem
is centred around the dung beetles.

549
00:42:34,800 --> 00:42:37,760
Without these amazingly
efficient recyclers,

550
00:42:37,760 --> 00:42:41,040
the daily dose of 5,000 tonnes
of dung

551
00:42:41,040 --> 00:42:43,280
would soon swamp
the African plains.

552
00:42:45,800 --> 00:42:48,320
Thanks to the cleaning up operations
of dung beetles,

553
00:42:48,320 --> 00:42:50,760
the grasslands are nurtured,

554
00:42:50,760 --> 00:42:53,400
allowing the grazers to be fed,

555
00:42:53,400 --> 00:42:56,480
which in turn sustain the predators.

556
00:43:09,320 --> 00:43:12,680
And it's in death where another team
of arthropod recyclers

557
00:43:12,680 --> 00:43:13,840
come into their own.

558
00:43:23,160 --> 00:43:26,520
Blow flies can smell a dead body
from up to a mile away.

559
00:43:28,680 --> 00:43:31,440
As soon as they arrive,
there's a frenzy of egg laying

560
00:43:31,440 --> 00:43:35,120
as each female deposits
up to 300 eggs on the carcass.

561
00:43:40,200 --> 00:43:42,680
In just under 24 hours
the eggs hatch,

562
00:43:42,680 --> 00:43:46,280
allowing the voracious maggots
to get to work on the flesh.

563
00:43:49,040 --> 00:43:51,920
Using special enzymes
and their claw-like mouthparts,

564
00:43:51,920 --> 00:43:56,000
they can break down proteins
in next to no time.

565
00:43:56,000 --> 00:43:58,640
In less than a week,
they'll have moulted twice,

566
00:43:58,640 --> 00:44:01,120
consumed 60% of the carcass

567
00:44:01,120 --> 00:44:03,400
and increased tenfold in size.

568
00:44:06,000 --> 00:44:09,400
With feeding over, the maggot begins
its next stage of life.

569
00:44:12,400 --> 00:44:16,080
Within a few days, a fly emerges.

570
00:44:16,080 --> 00:44:20,280
This will go on to mate and produce
the next generation of recyclers.

571
00:44:22,640 --> 00:44:25,760
So efficient are these recyclers
that, despite their size,

572
00:44:25,760 --> 00:44:28,080
arthropods process more flesh

573
00:44:28,080 --> 00:44:30,520
than all the large carnivores
put together.

574
00:44:41,240 --> 00:44:43,040
By cleaning up dead animals,

575
00:44:43,040 --> 00:44:46,280
the waste disposal teams
of the arthropod world

576
00:44:46,280 --> 00:44:47,920
limit the spread of disease

577
00:44:47,920 --> 00:44:51,320
and ensure the return of nutrients
back into the food chain.

578
00:44:52,560 --> 00:44:56,240
This is all part of keeping
nature's microworlds in balance

579
00:44:56,240 --> 00:44:59,960
but there is a twist in this tale.

580
00:44:59,960 --> 00:45:03,520
The arthropods' efficiency
and ability to reproduce quickly

581
00:45:03,520 --> 00:45:07,560
means that their populations
could easily spiral out of control.

582
00:45:08,880 --> 00:45:11,200
So who keeps the arthropods
in check?

583
00:45:14,400 --> 00:45:16,840
The answer
is the arthropods themselves.

584
00:45:20,120 --> 00:45:21,600
The woodlands of England.

585
00:45:27,520 --> 00:45:31,000
Spiders mostly prey on insects
and other spiders

586
00:45:31,000 --> 00:45:34,200
and they use a range of strategies
to capture their prey.

587
00:45:35,680 --> 00:45:38,440
The best-known is this -
the sticky web.

588
00:45:39,960 --> 00:45:43,400
An orb web can contain
up to 60 metres of silk

589
00:45:43,400 --> 00:45:46,040
and involve 3,000
different attachments.

590
00:45:47,480 --> 00:45:51,040
It takes about an hour to build
and then it's just a waiting game.

591
00:45:55,440 --> 00:45:58,640
She sits at the centre
with her legs resting on the spokes.

592
00:46:00,480 --> 00:46:02,920
Ready to pick up
the tiniest vibration.

593
00:46:05,560 --> 00:46:09,840
As soon as a tremor spreads down the
web, she pulls on different spokes.

594
00:46:12,560 --> 00:46:16,320
In this way, she can work out
exactly where her prey has landed.

595
00:46:17,960 --> 00:46:20,280
With her feet coated
in a special oil,

596
00:46:20,280 --> 00:46:22,000
she can move freely across her web

597
00:46:22,000 --> 00:46:25,440
to secure
and then devour her victim.

598
00:46:28,200 --> 00:46:30,760
While this capture
has gone perfectly to plan,

599
00:46:30,760 --> 00:46:32,400
it's not always the case.

600
00:46:34,840 --> 00:46:38,200
About half the potential prey
manage to escape.

601
00:46:44,680 --> 00:46:48,040
But there's another web
that's a more effective trap

602
00:46:48,040 --> 00:46:51,360
and it's designed
by the aptly-named triangle spider.

603
00:46:54,320 --> 00:46:57,760
Its web may not look as impressive
as the classic orb web

604
00:46:57,760 --> 00:46:59,880
but it is far more deadly.

605
00:47:02,080 --> 00:47:05,560
The spider's body forms
an essential link in her trap.

606
00:47:05,560 --> 00:47:08,600
But to be effective,
she has to ratchet up the tension.

607
00:47:09,680 --> 00:47:11,320
Tighter...

608
00:47:11,320 --> 00:47:12,800
and tighter.

609
00:47:18,960 --> 00:47:22,720
On this web,
flies don't get a second chance.

610
00:47:25,120 --> 00:47:28,240
Their impact triggers
the spider's release,

611
00:47:28,240 --> 00:47:30,920
causing the web to fire
and entangle the prey.

612
00:47:32,200 --> 00:47:35,440
Few flies manage to escape.

613
00:47:35,440 --> 00:47:38,360
Which is pretty good
for an individual's web

614
00:47:38,360 --> 00:47:40,480
but when spiders team together,

615
00:47:40,480 --> 00:47:42,880
the results
are even more impressive.

616
00:47:46,720 --> 00:47:49,000
In the rainforests of South America,

617
00:47:49,000 --> 00:47:54,240
a section of the canopy is enveloped
in a massive tangle of webs.

618
00:47:56,080 --> 00:47:57,560
This tree-top death trap

619
00:47:57,560 --> 00:48:01,200
is the work of tens of thousands
of tiny spiders.

620
00:48:09,040 --> 00:48:12,960
Spanning three metres across,
it can capture a whole host of prey.

621
00:48:19,200 --> 00:48:20,960
Including this cricket,

622
00:48:20,960 --> 00:48:24,040
which is several hundred times
larger than the spiders.

623
00:48:25,280 --> 00:48:27,520
But that doesn't put
these spiders off.

624
00:48:29,840 --> 00:48:33,440
Working together, they can kill prey
many times their own size.

625
00:48:40,400 --> 00:48:43,480
They squirt glue
from their spinnerets,

626
00:48:43,480 --> 00:48:44,800
immobilising the cricket,

627
00:48:44,800 --> 00:48:46,600
and then they inject their venom.

628
00:48:52,960 --> 00:48:55,360
Before long, their victim is dead

629
00:48:55,360 --> 00:48:58,160
and now they begin
their communal feast.

630
00:49:15,520 --> 00:49:18,120
Numbering over 40,000 species,

631
00:49:18,120 --> 00:49:22,800
spiders are found across the globe
and exist in nearly every habitat.

632
00:49:24,680 --> 00:49:27,400
Thanks to their silken traps
and venom,

633
00:49:27,400 --> 00:49:29,320
these predators play a pivotal role

634
00:49:29,320 --> 00:49:32,160
in keeping the planet's
many microworlds in balance.

635
00:49:35,360 --> 00:49:38,160
The controllers of the arthropod
world are a key piece of the puzzle

636
00:49:38,160 --> 00:49:40,680
that keeps our planet ticking over

637
00:49:40,680 --> 00:49:42,640
but they're not the most important.

638
00:49:45,680 --> 00:49:47,960
To find out what is,
we need to explore

639
00:49:47,960 --> 00:49:51,080
a far more harmonious relationship,

640
00:49:51,080 --> 00:49:54,240
one that began in prehistoric times.

641
00:49:59,360 --> 00:50:03,440
140 million years ago, the world
was a very different place.

642
00:50:03,440 --> 00:50:07,880
The plant kingdom was dominated by
a few species of conifers and ferns.

643
00:50:09,400 --> 00:50:15,000
For these plants, sexual reproduction
relies upon either the wind or water.

644
00:50:18,400 --> 00:50:20,440
With millions of tiny pollen grains

645
00:50:20,440 --> 00:50:22,880
dispersed in the hope
that some are intercepted

646
00:50:22,880 --> 00:50:25,080
by individuals of the same species.

647
00:50:27,080 --> 00:50:28,800
Rich in oils and proteins,

648
00:50:28,800 --> 00:50:33,160
pollen grains are expensive to
produce and the majority are wasted.

649
00:50:39,800 --> 00:50:42,400
But then an incredible
relationship began,

650
00:50:42,400 --> 00:50:45,440
which would change the colour
and diversity of our planet

651
00:50:45,440 --> 00:50:49,440
and ultimately create
the richest ecosystem of all.

652
00:50:51,840 --> 00:50:55,480
The presence of insects allowed
a new kind of plant to evolve.

653
00:50:58,760 --> 00:51:00,080
The flowering plants.

654
00:51:02,640 --> 00:51:05,080
To reduce the squandering of pollen,

655
00:51:05,080 --> 00:51:08,560
these plants no longer relied on
wind or water for pollination,

656
00:51:08,560 --> 00:51:12,800
instead they recruited insects
to pollinate them

657
00:51:12,800 --> 00:51:15,440
with nectar-loaded flowers.

658
00:51:17,840 --> 00:51:21,840
Tailoring their advertisements
to match insect senses,

659
00:51:21,840 --> 00:51:25,480
a burst of colour and smell
quickly spread across the planet.

660
00:51:41,280 --> 00:51:43,400
In the fields of southern France,

661
00:51:43,400 --> 00:51:45,840
sunflowers grow
to face the rising sun.

662
00:51:50,120 --> 00:51:51,680
One after another,

663
00:51:51,680 --> 00:51:55,560
hundreds of individual florets
produce pollen-covered stamens.

664
00:51:58,160 --> 00:52:00,280
As these bees busily feed on nectar,

665
00:52:00,280 --> 00:52:03,480
they brush against the stamens
collecting pollen

666
00:52:03,480 --> 00:52:06,120
and then carry it
from flower to flower.

667
00:52:08,160 --> 00:52:11,600
The sunflower's fertilised
and the bee is fed -

668
00:52:11,600 --> 00:52:14,240
it's a win-win situation.

669
00:52:17,480 --> 00:52:22,040
Over the generations, this
mutually beneficial relationship

670
00:52:22,040 --> 00:52:25,560
has created some incredibly
specialised partnerships

671
00:52:25,560 --> 00:52:29,320
between arthropods
and the flowers they pollinate.

672
00:52:29,320 --> 00:52:34,360
One of which can be found
in the grasslands of England.

673
00:52:37,480 --> 00:52:39,920
The pyramidal orchid
keeps its nectar rewards

674
00:52:39,920 --> 00:52:42,920
at the end of long tubes
formed by the petals,

675
00:52:42,920 --> 00:52:46,400
so that a long tongue is needed
to get it out.

676
00:52:48,920 --> 00:52:51,280
The burnet moth has one such tongue.

677
00:52:52,800 --> 00:52:55,720
As it feeds, a horseshoe-shaped
package of pollen

678
00:52:55,720 --> 00:52:58,320
clips onto its long proboscis.

679
00:53:00,120 --> 00:53:02,640
The only way the moth
can remove the pollen

680
00:53:02,640 --> 00:53:05,640
is by visiting other
pyramidal orchids.

681
00:53:08,280 --> 00:53:11,120
This time, as its tongue
reaches for a nectar drink,

682
00:53:11,120 --> 00:53:13,160
the pollen sacks come into contact

683
00:53:13,160 --> 00:53:15,400
with the flower's sticky
female surface

684
00:53:15,400 --> 00:53:18,400
and a speck of pollen is transferred
across.

685
00:53:19,640 --> 00:53:21,440
The flower is pollinated.

686
00:53:38,040 --> 00:53:40,080
But an even more
elaborate partnership

687
00:53:40,080 --> 00:53:43,000
has evolved in the rainforests
of Central America.

688
00:53:45,440 --> 00:53:50,320
This strange-looking flower
is a bucket orchid.

689
00:53:50,320 --> 00:53:55,200
Instead of nectar, it has another
offering for its arthropod partner.

690
00:53:56,240 --> 00:53:59,520
The euglossine bee is attracted
to special fragrant oils

691
00:53:59,520 --> 00:54:01,720
on the orchid's petals.

692
00:54:01,720 --> 00:54:04,320
It gathers these oils into pouches
on its legs

693
00:54:04,320 --> 00:54:08,200
and will later use this perfume
to attract female bees.

694
00:54:09,800 --> 00:54:12,480
Other creatures are attracted
to this flower

695
00:54:12,480 --> 00:54:16,800
but after slipping into the flower's
fluid-filled buckets, few survive.

696
00:54:20,640 --> 00:54:23,840
While the bee depends
on the orchid for its reproduction,

697
00:54:23,840 --> 00:54:26,160
the orchid likewise depends
on the bee.

698
00:54:29,520 --> 00:54:31,160
Unlike other insects,

699
00:54:31,160 --> 00:54:34,400
falling into the orchid's trap
is not fatal for this bee.

700
00:54:34,400 --> 00:54:37,840
The bucket orchid
has an escape route

701
00:54:37,840 --> 00:54:40,920
specifically designed
for its partner.

702
00:54:40,920 --> 00:54:46,000
Most of the flower
is covered in a slippery fluid

703
00:54:46,000 --> 00:54:51,080
but tiny knobs, which the bee
can grab onto, guide it to an exit.

704
00:54:53,840 --> 00:54:55,640
And, as it squeezes through the gap,

705
00:54:55,640 --> 00:54:57,000
just big enough for the bee,

706
00:54:57,000 --> 00:55:00,600
the flower's pollen
is glued onto its back.

707
00:55:26,480 --> 00:55:29,280
On its next visit
to a bucket orchid,

708
00:55:29,280 --> 00:55:31,280
the bee fulfils
its part of the deal.

709
00:55:34,760 --> 00:55:39,200
While gathering more aromatic oils,
it's lured into the flower again.

710
00:55:43,480 --> 00:55:45,480
And this time, as it leaves,

711
00:55:45,480 --> 00:55:48,560
the pollen packets are deposited
onto the new flower.

712
00:55:53,400 --> 00:55:55,480
The orchid is fertilised.

713
00:55:59,320 --> 00:56:01,520
And it's through this process,
pollination,

714
00:56:01,520 --> 00:56:04,960
that arthropods have exerted
their greatest influence of all.

715
00:56:09,280 --> 00:56:10,960
For over 100 million years,

716
00:56:10,960 --> 00:56:15,520
the pollinators and their flowering
partners have evolved,

717
00:56:15,520 --> 00:56:17,080
diversified...

718
00:56:18,560 --> 00:56:21,040
..and spread across the planet.

719
00:56:30,840 --> 00:56:34,040
With their success
came an explosion of life,

720
00:56:34,040 --> 00:56:37,160
as they created new opportunities,

721
00:56:37,160 --> 00:56:39,320
new habitats

722
00:56:39,320 --> 00:56:41,360
and new ecosystems.

723
00:56:42,800 --> 00:56:45,400
Today there are over
a quarter of a million species

724
00:56:45,400 --> 00:56:47,280
of arthropod pollinators.

725
00:56:47,280 --> 00:56:51,280
80% of all plant species on Earth
depend on them

726
00:56:51,280 --> 00:56:55,440
and without them some of the richest
ecosystems on our planet,

727
00:56:55,440 --> 00:56:59,000
including the tropical rainforests,

728
00:56:59,000 --> 00:57:00,960
would not even exist.

729
00:57:00,960 --> 00:57:03,680
From the harvesters and providers

730
00:57:03,680 --> 00:57:07,240
to the recyclers and controllers...

731
00:57:08,560 --> 00:57:12,640
..each group of arthropods
has a truly astonishing influence

732
00:57:12,640 --> 00:57:15,480
on the workings of our planet.

733
00:57:16,640 --> 00:57:18,760
But it's ultimately the pollinators

734
00:57:18,760 --> 00:57:22,400
that have the greatest
influence of all.

735
00:57:58,200 --> 00:58:00,840
Our planet is the greatest

736
00:58:00,840 --> 00:58:02,920
living puzzle in the universe.

737
00:58:02,920 --> 00:58:04,040
A collection of worlds

738
00:58:04,040 --> 00:58:06,160
within worlds,

739
00:58:06,160 --> 00:58:07,800
each one a network

740
00:58:07,800 --> 00:58:10,680
of relationships and connections

741
00:58:10,680 --> 00:58:12,560
between all their living parts,

742
00:58:12,560 --> 00:58:15,280
leading to the diverse

743
00:58:15,280 --> 00:58:17,520
and complex world we live in.

744
00:58:18,840 --> 00:58:20,960
And at the heart of
many of these worlds

745
00:58:20,960 --> 00:58:24,240
is a very special group of animals -

746
00:58:24,240 --> 00:58:26,680
the insects,
and their close relatives -

747
00:58:26,680 --> 00:58:30,320
the arachnids and crustaceans,

748
00:58:30,320 --> 00:58:34,600
classed together as the arthropods.

749
00:58:34,600 --> 00:58:37,440
Together, they account for 80% of

750
00:58:37,440 --> 00:58:40,280
all animal species on our planet.

751
00:58:40,280 --> 00:58:41,840
In these three specials,

752
00:58:41,840 --> 00:58:45,440
we're going to explore
the connections and relationships

753
00:58:45,440 --> 00:58:46,720
that they have with us,

754
00:58:46,720 --> 00:58:48,640
our planet...

755
00:58:49,840 --> 00:58:52,480
..and with each other,

756
00:58:52,480 --> 00:58:55,600
ultimately, to understand
how this group

757
00:58:55,600 --> 00:59:01,600
hold the key to life itself
inside nature's microworlds.

758
00:59:09,040 --> 00:59:11,120
Arthropods are the most abundant

759
00:59:11,120 --> 00:59:12,760
and diverse

760
00:59:12,760 --> 00:59:14,520
group of animals in the world.

761
00:59:15,840 --> 00:59:17,120
They inhabit

762
00:59:17,120 --> 00:59:20,200
every continent and every ocean...

763
00:59:22,240 --> 00:59:24,360
..from the harsh climate

764
00:59:24,360 --> 00:59:25,760
of Antarctica...

765
00:59:27,480 --> 00:59:31,280
..to the driest of deserts
around the equator.

766
00:59:32,320 --> 00:59:35,480
From the lushest jungles

767
00:59:35,480 --> 00:59:38,280
to the highest mountain peaks.

768
00:59:44,040 --> 00:59:46,720
There are an estimated
ten million species.

769
00:59:49,280 --> 00:59:52,000
More than all the other
animal groups combined.

770
00:59:55,560 --> 00:59:57,920
But what is
the secret of their success?

771
00:59:59,840 --> 01:00:02,240
What is the single key
to their global domination?

772
01:00:05,480 --> 01:00:09,160
To understand this,
we need to unpick, one by one,

773
01:00:09,160 --> 01:00:13,040
the factors that influence
the lives of arthropods.

774
01:00:16,760 --> 01:00:20,000
First, we need to understand
what arthropods are

775
01:00:20,000 --> 01:00:21,600
and where they came from.

776
01:00:25,720 --> 01:00:27,120
And to do that,

777
01:00:27,120 --> 01:00:28,760
we must travel to Delaware Bay,

778
01:00:28,760 --> 01:00:30,680
on the east coast of America.

779
01:00:38,040 --> 01:00:40,760
400 million years ago,

780
01:00:40,760 --> 01:00:42,000
the first land animals

781
01:00:42,000 --> 01:00:44,000
pulled themselves out of the sea.

782
01:00:47,400 --> 01:00:50,600
They were the ancestors of
the arthropods

783
01:00:50,600 --> 01:00:52,480
who dominate our planet today.

784
01:00:57,800 --> 01:01:01,840
And each spring, on the highest
tides of the full and new moons,

785
01:01:01,840 --> 01:01:03,840
a similar spectacle still occurs.

786
01:01:07,760 --> 01:01:09,600
These are horseshoe crabs -

787
01:01:09,600 --> 01:01:12,760
some of the most primitive
arthropods alive today.

788
01:01:14,600 --> 01:01:16,920
They're here to breed.

789
01:01:19,520 --> 01:01:23,160
The males are two-thirds
the size of their mates

790
01:01:23,160 --> 01:01:27,280
and cluster along the water's edge
as the females arrive.

791
01:01:27,280 --> 01:01:30,120
Clinging to the female's shell,

792
01:01:30,120 --> 01:01:31,640
he's pulled up the beach,

793
01:01:31,640 --> 01:01:33,560
fertilising her eggs as she lays.

794
01:01:43,280 --> 01:01:44,560
For these crabs,

795
01:01:44,560 --> 01:01:46,800
breeding on land is only possible

796
01:01:46,800 --> 01:01:49,360
because of the arthropod blueprint.

797
01:01:56,200 --> 01:01:58,200
Their basic body plan

798
01:01:58,200 --> 01:02:01,080
is the same as all arthropods -

799
01:02:01,080 --> 01:02:04,600
a hard exoskeleton,

800
01:02:04,600 --> 01:02:06,680
segmented body,

801
01:02:06,680 --> 01:02:09,080
and jointed legs.

802
01:02:11,120 --> 01:02:15,960
A body plan that's persisted
unchanged for 400 million years.

803
01:02:15,960 --> 01:02:20,560
A body plan
as adaptable as it is simple.

804
01:02:22,840 --> 01:02:26,920
The key design feature
is no doubt the exoskeleton.

805
01:02:29,360 --> 01:02:32,440
A hard external skeleton,

806
01:02:32,440 --> 01:02:36,080
largely made of chitin,
that provides protection,

807
01:02:36,080 --> 01:02:37,760
support for muscles,

808
01:02:37,760 --> 01:02:42,000
but most importantly,
prevents water loss from the body.

809
01:02:45,840 --> 01:02:48,760
The ability of the exoskeleton
to retain water

810
01:02:48,760 --> 01:02:51,320
is the factor
that allows these crabs

811
01:02:51,320 --> 01:02:53,000
to lay their eggs on land

812
01:02:53,000 --> 01:02:55,360
and ultimately allowed arthropods

813
01:02:55,360 --> 01:02:58,120
to be the first animals
to colonise the land.

814
01:03:02,720 --> 01:03:05,920
But even this master of design,

815
01:03:05,920 --> 01:03:07,600
the exoskeleton, has a weakness.

816
01:03:09,440 --> 01:03:12,680
How do you grow
inside a suit of armour?

817
01:03:20,120 --> 01:03:21,960
To see that,

818
01:03:21,960 --> 01:03:24,560
we must travel
400 miles south

819
01:03:24,560 --> 01:03:27,720
to a freshwater microworld
in South Carolina.

820
01:03:40,640 --> 01:03:44,600
This crayfish
is getting ready to transform -

821
01:03:44,600 --> 01:03:46,680
something all arthropods must do

822
01:03:46,680 --> 01:03:48,920
to increase their size.

823
01:03:54,320 --> 01:03:57,640
In preparation,
he withdraws calcium from his shell

824
01:03:57,640 --> 01:04:01,240
and stores it in little white
tablets on the side of his head.

825
01:04:03,120 --> 01:04:06,040
His hard exoskeleton then splits,

826
01:04:06,040 --> 01:04:10,000
and the larger
soft-bodied crayfish emerges.

827
01:04:13,000 --> 01:04:15,200
It can take up to a few days for

828
01:04:15,200 --> 01:04:18,040
the new exoskeleton to fully harden,

829
01:04:18,040 --> 01:04:19,400
and before this occurs,

830
01:04:19,400 --> 01:04:21,360
the crayfish is vulnerable.

831
01:04:26,840 --> 01:04:30,080
This queen snake
is on a hunt for a meal.

832
01:04:34,160 --> 01:04:36,560
The hardened armour of the crayfish
is too much for her,

833
01:04:36,560 --> 01:04:39,880
but she can detect the chemicals

834
01:04:39,880 --> 01:04:41,680
given off by the soft body

835
01:04:41,680 --> 01:04:44,360
of a freshly moulted crayfish

836
01:04:44,360 --> 01:04:46,920
and knows this is her chance.

837
01:05:01,160 --> 01:05:02,880
As soft as a doughnut,

838
01:05:02,880 --> 01:05:06,440
this crayfish provides
a hearty meal.

839
01:05:09,840 --> 01:05:12,360
So the exoskeleton,

840
01:05:12,360 --> 01:05:15,440
vital to their success,

841
01:05:15,440 --> 01:05:17,640
also leaves them vulnerable.

842
01:05:21,000 --> 01:05:25,720
And it has another significant
defining effect on all arthropods.

843
01:05:28,160 --> 01:05:30,280
It restricts their size.

844
01:05:36,000 --> 01:05:41,360
This is the largest terrestrial
arthropod - the coconut crab.

845
01:05:43,400 --> 01:05:45,240
This crab will moult each year,

846
01:05:45,240 --> 01:05:48,160
and can live until he's 60,

847
01:05:48,160 --> 01:05:52,160
yet is still no larger than
a newborn baby.

848
01:05:52,160 --> 01:05:54,120
If you must transform

849
01:05:54,120 --> 01:05:56,600
every time you need to grow,

850
01:05:56,600 --> 01:05:59,640
then there's a limit to
how big you can get.

851
01:06:02,040 --> 01:06:04,120
But this apparent size disadvantage

852
01:06:04,120 --> 01:06:06,280
can be seen as an asset.

853
01:06:08,800 --> 01:06:12,160
It opens up a whole new world
for the arthropods.

854
01:06:21,600 --> 01:06:23,400
And to see how,

855
01:06:23,400 --> 01:06:24,800
we must travel to

856
01:06:24,800 --> 01:06:27,160
the Flow Country,
in Scotland.

857
01:06:37,720 --> 01:06:39,920
This is the fairy wasp,

858
01:06:39,920 --> 01:06:41,920
a quarter of a millimetre long.

859
01:06:41,920 --> 01:06:44,520
They spend nearly
all their lives underwater.

860
01:06:47,520 --> 01:06:52,080
She is one of the smallest known
arthropods alive on the planet

861
01:06:52,080 --> 01:06:53,840
and almost invisible
to the naked eye.

862
01:06:53,840 --> 01:06:56,520
She makes a tiny water flea

863
01:06:56,520 --> 01:06:58,280
look like a giant.

864
01:06:59,560 --> 01:07:01,560
This female is looking for

865
01:07:01,560 --> 01:07:04,440
a very specific place
to lay her eggs.

866
01:07:05,720 --> 01:07:07,360
She positions

867
01:07:07,360 --> 01:07:09,080
her microscopic ovipositor

868
01:07:09,080 --> 01:07:11,440
to pierce into the stem of a plant,

869
01:07:11,440 --> 01:07:14,080
where the eggs of a water beetle
have been laid.

870
01:07:15,800 --> 01:07:17,760
She deposits up to 100 eggs

871
01:07:17,760 --> 01:07:20,480
inside a single beetle egg.

872
01:07:25,760 --> 01:07:29,600
When the young hatch,
they have a ready source of food -

873
01:07:29,600 --> 01:07:32,600
the water beetle's
undeveloped young.

874
01:07:35,000 --> 01:07:37,280
It's only the size of this wasp

875
01:07:37,280 --> 01:07:40,400
that opens up this niche
for her to exploit.

876
01:07:43,800 --> 01:07:47,360
In fact, the arthropods'
diminutive size

877
01:07:47,360 --> 01:07:50,640
gives them a real trump card
in the game of life.

878
01:07:50,640 --> 01:07:53,640
It allows them
to exploit microhabitats.

879
01:07:55,200 --> 01:07:56,720
Be it an egg,

880
01:07:56,720 --> 01:07:59,720
a gall on an oak tree,

881
01:07:59,720 --> 01:08:01,120
or a single leaf.

882
01:08:02,320 --> 01:08:04,360
The wealth of habitats and niches

883
01:08:04,360 --> 01:08:07,920
available to them
is virtually infinite.

884
01:08:13,120 --> 01:08:16,160
But being small
also makes them vulnerable.

885
01:08:18,960 --> 01:08:20,200
Their size and abundance

886
01:08:20,200 --> 01:08:22,720
makes them an ideal food source

887
01:08:22,720 --> 01:08:24,680
for a whole host of other animals...

888
01:08:30,920 --> 01:08:35,360
..including the biggest animal
to have ever lived.

889
01:08:37,280 --> 01:08:39,600
The blue whale.

890
01:08:44,240 --> 01:08:47,720
So if size is not the ultimate
key to their success,

891
01:08:47,720 --> 01:08:51,880
we must look elsewhere and examine

892
01:08:51,880 --> 01:08:54,360
why the diversity of arthropods

893
01:08:54,360 --> 01:08:59,240
has evolved so much faster
than in all other animal groups.

894
01:09:01,280 --> 01:09:04,160
How do the arthropods
speed up their evolution?

895
01:09:08,200 --> 01:09:11,200
To find out,
we must travel to a microworld

896
01:09:11,200 --> 01:09:13,960
in our very own back gardens.

897
01:09:18,120 --> 01:09:20,920
This is a female cabbage aphid.

898
01:09:23,240 --> 01:09:26,320
In spring, she produces

899
01:09:26,320 --> 01:09:28,880
100 offspring in just a week.

900
01:09:30,560 --> 01:09:33,160
Her offspring
already have babies inside them,

901
01:09:33,160 --> 01:09:34,440
so this mother aphid

902
01:09:34,440 --> 01:09:36,520
is nurturing her granddaughters

903
01:09:36,520 --> 01:09:38,440
even before they're born.

904
01:09:41,160 --> 01:09:43,480
If all her descendants
survived and bred,

905
01:09:43,480 --> 01:09:44,960
by the end of the summer,

906
01:09:44,960 --> 01:09:50,680
there'd be
1,560 billion trillion aphids!

907
01:09:53,720 --> 01:09:57,120
She is the ultimate
breeding machine.

908
01:09:58,720 --> 01:10:02,160
This ability to reproduce
prolifically

909
01:10:02,160 --> 01:10:04,440
is a real trait of the arthropods.

910
01:10:08,520 --> 01:10:11,920
Having lots of offspring
and a quick life cycle

911
01:10:11,920 --> 01:10:15,200
increases the chances of
genetic mutations occurring.

912
01:10:17,400 --> 01:10:19,000
And it's these mutations,

913
01:10:19,000 --> 01:10:21,080
however bizarre they seem,

914
01:10:21,080 --> 01:10:24,360
that increase the diversity
of the gene pool.

915
01:10:25,800 --> 01:10:29,920
They can provide novel solutions

916
01:10:29,920 --> 01:10:31,520
to life's challenges...

917
01:10:38,760 --> 01:10:40,680
..and ultimately lead to

918
01:10:40,680 --> 01:10:43,200
the evolution of new species.

919
01:10:46,080 --> 01:10:50,600
This means that arthropods have the
ability to respond to opportunities

920
01:10:50,600 --> 01:10:54,280
and potentially fill niches faster
than any other group of animals.

921
01:10:55,720 --> 01:10:58,840
This does gives them a winning hand

922
01:10:58,840 --> 01:11:02,160
and provides another
vital piece in our jigsaw.

923
01:11:06,120 --> 01:11:08,400
But it's not the whole story.

924
01:11:14,920 --> 01:11:21,720
We've seen how arthropods have been
around for over 400 million years,

925
01:11:21,720 --> 01:11:23,800
how their winning body plan

926
01:11:23,800 --> 01:11:25,880
has stood them in good stead
for all this time.

927
01:11:29,240 --> 01:11:33,200
We've seen how their size enables
them to exploit microhabitats,

928
01:11:33,200 --> 01:11:37,080
and rapid reproduction
has accelerated their evolution.

929
01:11:38,840 --> 01:11:41,920
All factors that have enabled them
to fly,

930
01:11:41,920 --> 01:11:44,640
squelch, crawl,

931
01:11:44,640 --> 01:11:46,920
and scuttle

932
01:11:46,920 --> 01:11:49,280
into the myriad of forms
we see today.

933
01:11:52,840 --> 01:11:54,960
But there's a twist in the tale.

934
01:11:57,960 --> 01:12:01,760
For the real key to their
global success and diversity,

935
01:12:01,760 --> 01:12:04,240
we must look much closer to home.

936
01:12:06,880 --> 01:12:08,520
To really understand

937
01:12:08,520 --> 01:12:11,000
the diversity of
the arthropods,

938
01:12:11,000 --> 01:12:13,120
we must examine
how the presence

939
01:12:13,120 --> 01:12:14,720
of other arthropods
affects them.

940
01:12:18,120 --> 01:12:20,880
Firstly, let's look at
what can be achieved

941
01:12:20,880 --> 01:12:23,440
when arthropods work together.

942
01:12:34,720 --> 01:12:37,360
This colony of 40,000 bees

943
01:12:37,360 --> 01:12:39,600
is focused on a single task -

944
01:12:39,600 --> 01:12:41,760
the production of honey.

945
01:12:44,880 --> 01:12:46,560
They have a single queen,

946
01:12:46,560 --> 01:12:48,680
who is the only bee to lay eggs.

947
01:12:50,200 --> 01:12:52,000
She can lay up to 2,000

948
01:12:52,000 --> 01:12:53,280
in a single day.

949
01:12:55,920 --> 01:12:59,560
Each bee is roughly
a centimetre and a half in length.

950
01:12:59,560 --> 01:13:02,560
Their exoskeleton prevents them
from growing any further

951
01:13:02,560 --> 01:13:03,960
in this adult form.

952
01:13:06,640 --> 01:13:10,720
But there's an animal over a million
times its weight on the prowl...

953
01:13:13,920 --> 01:13:16,120
..and he's after their honey.

954
01:13:20,800 --> 01:13:24,240
To lose their honey now
would be fatal for their colony.

955
01:13:24,240 --> 01:13:27,160
It'll be their only source of food

956
01:13:27,160 --> 01:13:29,200
during the cold winter months.

957
01:13:29,200 --> 01:13:32,000
But this super society won't give up

958
01:13:32,000 --> 01:13:34,640
its hard-won prize without a fight.

959
01:13:37,360 --> 01:13:40,920
They attack and sting en masse.

960
01:13:40,920 --> 01:13:44,200
The first stinger
releases an alarm pheromone

961
01:13:44,200 --> 01:13:47,600
that tells other bees to join in.

962
01:13:47,600 --> 01:13:49,240
The stings are barbed

963
01:13:49,240 --> 01:13:51,720
and hook into the skin of the bear.

964
01:13:59,520 --> 01:14:02,360
Each sting has its
own nervous system

965
01:14:02,360 --> 01:14:05,000
and pumps venom
into the attacker.

966
01:14:07,760 --> 01:14:10,200
Worker bees can only sting once...

967
01:14:12,480 --> 01:14:14,080
..and then they die.

968
01:14:15,320 --> 01:14:18,320
It's the ultimate sacrifice
for their colony.

969
01:14:20,320 --> 01:14:23,000
But the bees are victorious.

970
01:14:23,000 --> 01:14:25,440
The bear is repelled.

971
01:14:27,840 --> 01:14:29,480
Teamwork enables these bees

972
01:14:29,480 --> 01:14:32,200
to defend their precious honey

973
01:14:32,200 --> 01:14:35,600
against an intruder many
thousands of times their own size.

974
01:14:40,280 --> 01:14:44,360
So working together can offer
great advantages for defence.

975
01:14:46,040 --> 01:14:50,240
But it's one thing if your attacker
is an animal like a black bear

976
01:14:50,240 --> 01:14:53,160
and quite another
if it's the environment itself.

977
01:14:58,400 --> 01:15:02,240
So how does working as a team
allow you to live in

978
01:15:02,240 --> 01:15:04,840
one of the toughest environments
in the world?

979
01:15:06,920 --> 01:15:09,640
To find out, we must
travel 9,000 miles

980
01:15:09,640 --> 01:15:12,240
to the mangroves
of Australia.

981
01:15:14,600 --> 01:15:17,240
They may look like
a benign place to live,

982
01:15:17,240 --> 01:15:19,480
but they're actually packed with

983
01:15:19,480 --> 01:15:21,720
potentially deadly natural forces.

984
01:15:25,080 --> 01:15:28,440
Hot tropical sun, salty water,

985
01:15:28,440 --> 01:15:31,160
and the risk of drowning
with every high tide.

986
01:15:35,840 --> 01:15:37,960
But in the mangrove mud
is where these ants

987
01:15:37,960 --> 01:15:41,320
have chosen to build their nest.

988
01:15:41,320 --> 01:15:46,280
And teamwork has turned the tide
to their advantage.

989
01:15:48,960 --> 01:15:51,480
Each high tide
brings a fresh bounty of food

990
01:15:51,480 --> 01:15:53,600
that the ants can harvest.

991
01:15:56,800 --> 01:15:58,960
But this tide also brings
the threat of drowning

992
01:15:58,960 --> 01:16:02,960
and the precious ant larvae
being swept away.

993
01:16:04,240 --> 01:16:06,120
The ants have a cunning strategy.

994
01:16:18,360 --> 01:16:21,440
Every tide,
these ants combine their forces

995
01:16:21,440 --> 01:16:23,680
and move the entire nest,
larvae and all,

996
01:16:23,680 --> 01:16:26,000
into bell-shaped chambers
they've built,

997
01:16:26,000 --> 01:16:30,160
which trap the air, keeping them
safely above the waterline.

998
01:16:32,000 --> 01:16:36,160
Here, they'll remain for several
hours, until the tide retreats.

999
01:16:42,280 --> 01:16:46,240
So cooperation between arthropods
of the same species

1000
01:16:46,240 --> 01:16:48,840
offers great advantages.

1001
01:16:53,280 --> 01:16:55,080
But we must look elsewhere

1002
01:16:55,080 --> 01:16:58,160
for the ultimate key
to the success of the arthropods.

1003
01:17:00,400 --> 01:17:02,160
We must examine the idea

1004
01:17:02,160 --> 01:17:04,920
that diversity stems
not only from cooperation,

1005
01:17:04,920 --> 01:17:08,160
but also exploitation.

1006
01:17:14,240 --> 01:17:17,200
A female bolas spider.

1007
01:17:17,200 --> 01:17:19,360
She's hunting for food...

1008
01:17:21,200 --> 01:17:24,160
..and she's got
a pretty unique way of doing it.

1009
01:17:27,440 --> 01:17:30,720
She spins a single thread of silk,

1010
01:17:30,720 --> 01:17:32,200
thinner than a human hair,

1011
01:17:32,200 --> 01:17:33,920
with a sticky globule on the end.

1012
01:17:36,360 --> 01:17:40,200
And from special glands
on her abdomen,

1013
01:17:40,200 --> 01:17:42,200
she produces a pheromone
to attract her prey.

1014
01:17:45,960 --> 01:17:47,440
She waits.

1015
01:17:50,520 --> 01:17:52,240
An approaching moth,

1016
01:17:52,240 --> 01:17:55,440
but she hasn't quite got her eye in.

1017
01:18:02,400 --> 01:18:04,160
She doesn't miss twice.

1018
01:18:11,000 --> 01:18:14,240
So arthropods affect
their own diversity

1019
01:18:14,240 --> 01:18:16,080
by providing a food source.

1020
01:18:17,920 --> 01:18:20,760
And necessity being
the mother of all invention,

1021
01:18:20,760 --> 01:18:23,720
they've evolved
some diverse and ingenious ways

1022
01:18:23,720 --> 01:18:25,440
of catching each other.

1023
01:18:31,240 --> 01:18:35,720
But the exploitative relationships
between them don't end there.

1024
01:18:39,360 --> 01:18:41,400
The Mojave desert in California.

1025
01:18:42,800 --> 01:18:45,680
This is a female blister beetle.

1026
01:18:49,720 --> 01:18:52,560
She lays her eggs
in the scorching sand of the desert,

1027
01:18:52,560 --> 01:18:54,840
a few centimetres below the surface.

1028
01:18:57,480 --> 01:18:59,440
The perfect temperature
for incubation.

1029
01:19:00,680 --> 01:19:03,000
When the larvae hatch,

1030
01:19:03,000 --> 01:19:05,840
they need to find food - and fast.

1031
01:19:07,800 --> 01:19:09,840
En masse,
they climb the nearest stem of grass

1032
01:19:09,840 --> 01:19:11,760
and form a cluster.

1033
01:19:15,320 --> 01:19:17,360
They release a pheromone

1034
01:19:17,360 --> 01:19:20,440
identical to that produced by
a female digger bee,

1035
01:19:20,440 --> 01:19:22,480
and it isn't long
before they're noticed.

1036
01:19:24,960 --> 01:19:29,640
This is a male digger bee
and he's come to mate,

1037
01:19:29,640 --> 01:19:31,640
but instead of an amorous reception,

1038
01:19:31,640 --> 01:19:34,240
he's boarded by hundreds of larvae.

1039
01:19:36,800 --> 01:19:38,800
Temporarily stunned,

1040
01:19:38,800 --> 01:19:40,240
he falls to the floor,

1041
01:19:40,240 --> 01:19:41,920
but quickly regains his composure...

1042
01:19:43,120 --> 01:19:45,640
..and heads off
in search of another female.

1043
01:19:48,360 --> 01:19:50,200
While he's mating,

1044
01:19:50,200 --> 01:19:52,560
his stowaways jump ship.

1045
01:19:59,400 --> 01:20:02,000
The female then returns to
her burrow,

1046
01:20:02,000 --> 01:20:04,040
where she's secreted pollen

1047
01:20:04,040 --> 01:20:05,720
for her unhatched young.

1048
01:20:11,040 --> 01:20:14,360
The blister beetle's larvae
have reached safety

1049
01:20:14,360 --> 01:20:17,120
and a ready supply of food,

1050
01:20:17,120 --> 01:20:19,800
and when the pollen is finished,

1051
01:20:19,800 --> 01:20:22,240
they'll consume
the young of the digger bee.

1052
01:20:25,600 --> 01:20:27,520
So we know that predation

1053
01:20:27,520 --> 01:20:30,240
and exploitation lead to diversity.

1054
01:20:34,160 --> 01:20:36,280
But there's one final factor

1055
01:20:36,280 --> 01:20:39,520
that affects
the success of the arthropods.

1056
01:20:39,520 --> 01:20:42,240
One final vital key that unlocks
a greater understanding

1057
01:20:42,240 --> 01:20:45,480
of their world, and without which,

1058
01:20:45,480 --> 01:20:47,440
the array of life we see today

1059
01:20:47,440 --> 01:20:49,960
would not be present,

1060
01:20:49,960 --> 01:20:52,600
and it's diversity itself.

1061
01:21:06,560 --> 01:21:10,400
Diversity breeds diversity.

1062
01:21:10,400 --> 01:21:14,480
Arthropods are part of
a constant arms race

1063
01:21:14,480 --> 01:21:18,280
to outmanoeuvre
and exploit each other,

1064
01:21:18,280 --> 01:21:19,800
a process called coevolution.

1065
01:21:19,800 --> 01:21:23,160
To see coevolution
at work,

1066
01:21:23,160 --> 01:21:24,600
we must head to
a meadow

1067
01:21:24,600 --> 01:21:26,120
in the Swiss Alps.

1068
01:21:31,200 --> 01:21:34,840
This is a female
Alcon Blue butterfly.

1069
01:21:37,560 --> 01:21:40,080
She lays her eggs
on the gentian plant,

1070
01:21:40,080 --> 01:21:42,600
and when they've hatched
into caterpillars

1071
01:21:42,600 --> 01:21:45,400
and eaten their fill,
they drop onto the ground.

1072
01:21:47,160 --> 01:21:49,400
Surrounded by foraging ants,

1073
01:21:49,400 --> 01:21:51,880
you'd think they'd be at risk,

1074
01:21:51,880 --> 01:21:53,880
but the ants dutifully collect them

1075
01:21:53,880 --> 01:21:56,000
and transport them
back to their nest,

1076
01:21:56,000 --> 01:21:58,560
where they're cleaned and fed.

1077
01:22:04,560 --> 01:22:07,320
The Alcon Blue caterpillars
have bewitched the ants.

1078
01:22:08,960 --> 01:22:10,960
They emit chemicals
that convince the ants

1079
01:22:10,960 --> 01:22:13,440
they're one of their own larvae,

1080
01:22:13,440 --> 01:22:15,240
even producing noises

1081
01:22:15,240 --> 01:22:17,760
similar to those
made by the queen ant,

1082
01:22:17,760 --> 01:22:19,680
to ensure the royal treatment.

1083
01:22:21,240 --> 01:22:24,920
They've checked in
to a five-star ant hotel.

1084
01:22:28,560 --> 01:22:31,840
But the ingenuity of this
butterfly species

1085
01:22:31,840 --> 01:22:36,000
presents an opportunity to any other
species canny enough to exploit it.

1086
01:22:41,080 --> 01:22:43,800
This is an ichneumon wasp.

1087
01:22:46,160 --> 01:22:48,480
Out of hundreds of ants' nests,

1088
01:22:48,480 --> 01:22:50,200
she's able to detect the one

1089
01:22:50,200 --> 01:22:53,120
that contains
an Alcon butterfly caterpillar.

1090
01:22:57,720 --> 01:23:00,440
The ants' response
to any invader is to attack...

1091
01:23:03,440 --> 01:23:05,080
..but she releases a pheromone

1092
01:23:05,080 --> 01:23:06,680
that deranges the ants.

1093
01:23:09,400 --> 01:23:11,400
They begin to attack each other...

1094
01:23:14,200 --> 01:23:17,120
..and this buys her
the time she needs.

1095
01:23:23,360 --> 01:23:25,120
The wasp makes a beeline for

1096
01:23:25,120 --> 01:23:26,960
the butterfly larvae,

1097
01:23:26,960 --> 01:23:28,800
where she will lay her eggs.

1098
01:23:39,360 --> 01:23:42,040
Job complete, she leaves the nest.

1099
01:23:46,080 --> 01:23:49,320
The ants' nest,
released from the wasp's spell,

1100
01:23:49,320 --> 01:23:50,920
returns to normal.

1101
01:23:57,440 --> 01:23:59,840
The caterpillars remain in the nest

1102
01:23:59,840 --> 01:24:01,520
until the following summer,

1103
01:24:01,520 --> 01:24:03,120
when they transform into a pupa,

1104
01:24:03,120 --> 01:24:04,360
and after about a month,

1105
01:24:04,360 --> 01:24:06,640
the adult butterflies emerge.

1106
01:24:17,080 --> 01:24:19,400
But not every pupa contains

1107
01:24:19,400 --> 01:24:21,200
an Alcon Blue adult.

1108
01:24:23,360 --> 01:24:25,280
A young ichneumon wasp.

1109
01:24:37,800 --> 01:24:41,000
The exploiter
has become the exploited.

1110
01:24:46,040 --> 01:24:49,640
Diversity has presented opportunity.

1111
01:24:54,240 --> 01:24:57,640
The wasp has evolved
to exploit the butterfly...

1112
01:24:59,360 --> 01:25:01,840
..who exploits the ants.

1113
01:25:01,840 --> 01:25:04,240
Their lives are intricately linked.

1114
01:25:04,240 --> 01:25:07,440
They have coevolved.

1115
01:25:09,080 --> 01:25:11,720
And this is the final vital key

1116
01:25:11,720 --> 01:25:13,200
to the abundance

1117
01:25:13,200 --> 01:25:15,200
and diversity of the arthropods.

1118
01:25:15,200 --> 01:25:18,240
The process of coevolution.

1119
01:25:19,840 --> 01:25:21,120
All over the world,

1120
01:25:21,120 --> 01:25:24,360
the opportunities
presented by other arthropods

1121
01:25:24,360 --> 01:25:27,120
are creating the pressure
to innovate and evolve.

1122
01:25:29,400 --> 01:25:31,520
No doubt this diversity
wouldn't exist

1123
01:25:31,520 --> 01:25:34,960
if it weren't for
that winning body plan,

1124
01:25:34,960 --> 01:25:37,160
small size,

1125
01:25:37,160 --> 01:25:39,680
ability to reproduce,

1126
01:25:39,680 --> 01:25:41,600
work cooperatively,

1127
01:25:41,600 --> 01:25:44,960
and finally,
predate and exploit each other.

1128
01:25:48,360 --> 01:25:50,400
But it's this snowballing effect

1129
01:25:50,400 --> 01:25:51,600
of diversity itself

1130
01:25:51,600 --> 01:25:53,440
that raises arthropods onto

1131
01:25:53,440 --> 01:25:55,160
a whole new level.

1132
01:25:58,960 --> 01:26:00,400
The arthropods have lived,

1133
01:26:00,400 --> 01:26:03,160
survived and thrived on Earth

1134
01:26:03,160 --> 01:26:05,840
for 400 million years...

1135
01:26:05,840 --> 01:26:08,120
THUNDER BREAKS

1136
01:26:09,720 --> 01:26:11,800
..through extreme climate change,

1137
01:26:11,800 --> 01:26:14,520
volcanic events,

1138
01:26:14,520 --> 01:26:18,240
ice ages,

1139
01:26:18,240 --> 01:26:20,400
and the extinction of the dinosaurs.

1140
01:26:22,680 --> 01:26:27,520
In fact,
arthropods have survived and thrived

1141
01:26:27,520 --> 01:26:30,120
when 99.9% of all species

1142
01:26:30,120 --> 01:26:33,240
that ever lived have become extinct.

1143
01:26:35,280 --> 01:26:37,320
They are the most successful

1144
01:26:37,320 --> 01:26:40,760
and diverse group of animals
to have ever lived.