There are more kinds of insects in the world than all other kinds of animals put together.
But because they are so small,
we rarely see how extraordinary they are.
Occasionally, they assemble in astonishing numbers.
A billion monarch butterflies hibernate in the forests of Mexico.
Vast clouds of mayflies emerge all at once to mate.
Insects face endless challenges.
They can transform their bodies to meet every purpose -
eyes grow on stalks. Bodies become chemical guns.
To discover how and why they do such things,
you have to enter their world.
Patagonia, Chile, home to one of the most extraordinary of beetles.
There are many kinds of beetles in the world,
but this one has some of the biggest jaws of all.
He is Darwin's beetle.
He is on his way to the forest to look for a mate.
Whether he gets one or not will depend on his strength...
and on the size of his jaws.
He starts his search.
A female is likely to be on a tree trunk.
But trees, in this part of the world are very tall.
His search could be a long one.
Unfortunately for him, she is 25 metres above him
near the top.
She has more normal-sized jaws.
But then she only needs them for feeding.
But he needs immense jaws for fighting...
..because there are other males around with the same mission.
Sheer strength is not enough in these battles.
The technique is to reach over your opponent's head
and hook your jaws under his wing-covers.
That's why his jaws are so long
and have that odd shape.
He's got the grip.
Now he as to lift.
And that needs strength.
Another lift is needed.
And that's that.
Beetle armour is strong so he bounces.
The winner climbs on.
There are more males ready to fight him up here.
And here she is at last.
But she doesn't seem to be in the mood.
So now he has to use his great jaws as a restraining cage.
Success at last.
But the hurling habit dies hard.
Insects' bodies have the capacity to take on an almost infinite variety of shapes.
This is one of the keys to their success.
This male moth doesn't go in search of females.
He inflates a pair of scented plumes
that protrude from the end of his abdomen.
And they come to him!
All insects have the same basic design...
six legs and an armour-covered body.
But the different parts can become exaggerated
to solve particular problems.
This beetle has a giraffe's neck in order to fight.
A praying mantis is disguised as a flower
and waits in ambush.
Another is almost invisible among dead leaves.
Insects' armour can carry colours that can camouflage or communicate.
But the armour can also be converted into wings
and that makes insects a global force,
enabling them to invade almost every habitat on earth.
In Southern France,
one insect is starting on the most important day of its life.
Dawn, and a newly hatched damselfly.
She needs to mate and lay her eggs before sunset.
Her adult life is so short, she may not get another chance.
Her success will depend on these fragile wings.
She faces many perils.
Few insects can escape from a spider's web.
But her wings are more powerful than they look.
She wants to mate with the strongest male.
However, the stream, where she might find him, is a battle-ground.
She watches while dark-winged males compete for the best territories,
flashing their wings at each other in threat,
or trying to force their opponents into the water.
Fighting finished, the female uses her wings to signal her presence to the winner.
She won't be rushed.
But if he doesn't grip her with his tail, a rival might steal her.
As they mate, their linked bodies form the shape of a heart.
But now she has the problem of laying her fertilised eggs and that brings new hazards.
Like any athlete, she must warm her muscles for optimum performance
and does so by using her wings as solar-heating panels.
She must fly dangerously low if she's to find the right place for her eggs.
Only the quickest damselflies escape.
Safely past the frogs,
this female has reached a suitable plant on which to lay her eggs.
But she has to place them underwater if they are to survive.
For the first time, her wings seem to be a hindrance.
But in fact, they help her yet again,
by trapping a silvery layer of air which enables her to breathe.
She cuts into a plant stem and deposits her eggs inside.
Now her wings are going to be truly tested.
If she can't break through the water surface, she will drown.
Her day has been a complete success.
Damselflies seldom venture beyond their home stream.
But some insects fly huge distances.
September on the shores of Lake Erie in Southern Canada.
A monarch butterfly is fuelling up on nectar.
A chill gust of Northerly air.
It's time to leave.
The coming winter will be so cold it would kill her.
She has never flown more than a few hundred metres in her life.
But now she is heading out over Lake Erie,
which is a hundred miles across.
This is just the first leg of one of the greatest animal migrations.
She will continue South, using the sun as a compass,
to cross America, a journey of 2,000 miles.
Her destination is Mexico and one small and special group of trees.
No-one knows how she finds them, in these great mountain forests.
She joins other monarch butterflies that have travelled here from all over North America.
Countless butterflies crowd these particular trees,
hanging from every branch.
They come here because, although winter brings a chill to the air,
there will not be a lethal freeze as there will in Canada.
The conditions are perfect for hibernation.
Hibernating butterflies are vulnerable to predators.
But monarchs are poisonous.
However, a few birds have learned to rip out the toxic parts and eat the rest.
They kill hundreds of thousands of butterflies and dislodge many more.
Those that fall must get back into the trees before nightfall brings another killer.
They vibrate their wings to warm their flight muscles.
But it's a race against time.
Night brings a lethal ground frost.
Those that do survive, sleep safely huddled together in the trees, for four months.
The warmth of spring wakes them from their hibernation.
The majority of the butterflies that flew here from Canada have survived.
They take their first drink since their arrival last autumn.
With increasing warmth, more and more butterflies awake.
Soon they will all disperse northwards
and tranquillity will return to this forest
until the great grandchildren of these butterflies return to escape the freezing Northern winter.
Some insects, however, have made a speciality of living in the most adverse conditions.
Mono Lake is known as California's dead sea.
It's twice as salty as the ocean and lethal to almost all life.
Alkali flies are one of the few creatures able to tolerate these conditions
and since they have virtually no competitors,
they swarm in their millions.
Flies are one of the most successful of all insects.
There are 85,000 different kinds
and among them, a perfect fly for almost every habitat, even this one.
The alkali fly has special abilities that enable it to live on this lake.
It can walk underwater to eat algae.
Fine hairs trap air bubbles that prevent it from drowning.
But most critically, the fly has a physiology
that can neutralise the lethal levels of salt.
So the alkali fly's dominance of Mono Lake goes unchallenged
except for a few weeks of the year.
100,000 Wilson's phalarope are migrating to South America.
Mono Lake is their only stop-over.
These alkali flies, for them, are an invaluable and irresistible feast.
A fly has no defence, except to fly and become lost in a vast swarm.
It needs considerable skill to pluck an individual fly from the air.
There are gulls are here, too.
Though their fly-catching techniques are not so refined.
In four weeks, the phalaropes double their weight.
Then they set off again, heading south.
Leaving the gulls behind.
The size of the fly population has scarcely been affected.
For them, sheer abundance is defence enough.
BUZZING
But for some insects, defence is a much more complicated affair.
An oogpister beetle in South Africa.
He hunts ants.
Eating ants may give him more than just nourishment.
He may get something else from them that helps him fight his enemies.
The ants launch a counter-attack and nip his ankles.
But he simply kicks them out of the way.
The valiant ants drive him off...
straight into real danger.
A mongoose.
It's inquisitive.
But it's also wary of the oogpister.
A black and white pattern is a warning signal.
The beetle takes aim...
And fires formic acid straight at the mongoose's eyes and mouth.
The beetle probably collected this acid from the ants.
It certainly makes the beetle itself very distasteful and that, in turn, makes it worth mimicking.
This defenceless little lizard carries the beetles' warning pattern.
It also imitates the way the beetle runs.
Not particularly well, it's true, but well enough to
fool predators into thinking it just might be an acid-firing beetle.
All kinds of insects have developed chemical weapons.
A pair of devil-rider stick insects.
They fire bitter-tasting oils, terpenes.
European wood ants under attack from a hungry crow.
They fire the sort of acid that gives nettles their sting,
so this is like one of us falling into a nettle patch.
But the master of chemical warfare is the bombardier beetle.
It can create a chemical reaction within it's body so violent
that boiling caustic liquid explodes out of its abdomen.
By pulsing the jet 500 times a second,
it keeps its rear end just cool enough to prevent it being cooked.
In the woodlands of Minnesota,
there is an insect that has another chemical weapon.
But this one fights as an army and can stand up to almost any predator.
Bees collect nectar all day and transform it, within their stomachs,
into one of nature's richest foods, honey.
Hundreds of them are bringing their precious loads back to their colony in this hollow log.
The honey in their combs provides food for their young
and for the whole colony if the weather turns cold or there's a drought.
But so much food attracts thieves.
A black bear cub has a sweet tooth.
But he's never come across bees before
and he doesn't know that they will defend their honey to the death.
Stinging is the ultimate self-sacrifice for a bee,
because it can't pull out its barbed sting.
So its body is torn apart.
The bees' attack was far too much for the cub.
But a greater challenge is coming.
The cub's mother!
ANGRY BUZZING
The bees fight so hard that she only has time to steal a single comb.
While the family enjoy their honey at a safe distance,
the bees appear to have been defeated.
Their home has been destroyed
and their young will inevitably die out in the open.
Yet the colony is not doomed because the workers are now rescuing at least some of what really matters...
..their honey.
Each survivor is able to eat its own weight in honey, storing it in its stomach.
They will have to abandon their dying young,
but they will take much of their precious honey with them
to sustain themselves while they build a new colony.
Working together in such an organised society is the insects' great innovation.
So how did it begin?
It may have started in a place like this -
the nest of the Japanese red bug.
Parent insects don't usually care for their offspring but this bug is different.
The young feed on fallen fruit from just one kind of rare tree.
They could never find it by themselves. So their mother collects it for them.
She probes every fruit she finds
to test its ripeness
and rejects one after another.
This can take hours.
At last, a perfect fruit.
A thief!
It's easier to steal than find food for yourself.
For both bugs, the outcome of this dispute will be life-changing.
As the mother struggles to keep her prize,
her young, back in the nest, are growing restless.
The thief has won.
The mother doesn't know that her hungry young are leaving their nest in search of a better provider.
She returns
to find that her nest is empty.
Her young find the nest of the thief, who is herself a mother.
She returns to find that she has twice as many mouths to feed.
The loser has failed at her only chance of parenthood.
For the thief, life has suddenly got much harder.
A fruit won't now last as long as it did.
The young clamber over her, demanding more.
She returns with another fruit but her enlarged and
insatiable brood want still more.
So she has to work non-stop, day after day.
At last, the young become big enough to fend for themselves.
But their success has come at a cost.
The mother has worked herself to death.
And now her body has become their last meal before they leave home.
Looking after the young in such a way
is thought to be the first step towards living in a community.
But some insects benefit from doing the opposite of collaborating.
They kill one another.
Dawson's bee is one of the largest in the world.
It nests in the baked soil of the Australian outback.
Flowers are rare in this desert, so colonies of these bees are few and far between.
The bees excavate tunnels for their young.
The community is so harmonious that it's hard to believe that this place
is also the setting for mass murder.
Tempers do flare when a bee gets confused and goes down another's burrow.
But these are minor disagreements.
The colony is peaceful at the moment because every bee here is a female.
It's the males that are the killers and they are all dead.
Their story began two months earlier,
before the appearance of the females.
Male Dawson's bees.
The females are only just emerging, burrowing their way, one by one,
out of the tunnels where they hatched and grew up
and their scent enflames the males.
They are huge and built for fighting.
And each one wants to be in the best position to mate with a female.
A female emerges and immediately there's a brawl
as every male tries to reach her.
It's very rare for animals to kill their own kind in combat,
but stinging and biting rivals to death
is usually the only way these male bees get a female.
A winner manages to claim a female and the pair race for cover.
Meanwhile, the female's lingering scent drives one unsuccessful male
into a deadly frenzy.
Another female, caught in the middle of another brawl, becomes an accidental casualty.
By the time the last female has emerged, every male is dead.
The battles have ensured that the strongest males will have mated with the most females.
Two months later and it's an all female world
with the next generation already developing underground.
Insects have evolved sophisticated societies that, in complexity,
are the closest thing in nature to our own cities.
The insects that built this structure in Argentina
dominate the surrounding grasslands thanks to skills that seem almost more human than insect.
It's a metropolis,
a home to millions of ants.
The colony needs a huge supply of food.
It's surrounded by grass,
but the ants themselves can't digest a blade of it.
Nonetheless, they collect it.
Although they're all the same species, they exist in different shapes and sizes.
The heads of these big-jawed individuals are not full of brain...
but brawn.
They give the species its name.
They are grass cutters.
They work all day, every day.
The smaller ants, down on the ground, are porters with the job
of carrying the grass segments back to the colony.
They have great strength. Their main problem is balance.
Columns of them carry the grass back to the nest along highways
as straight as Roman roads.
Different members of the colony specialise in particular tasks in much the same way as people do.
But, as in human society, there can be problems.
A hitch-hiker makes one ant's job much harder.
And this isn't even grass.
A single colony harvests half a tonne of grass a year,
more than any other animal on these plains.
But since they themselves can't eat it, why do they do so?
The answer lies underground.
They have one of most extraordinary survival strategies in the insect world.
The ants have dug a network of tunnels
that extend downwards for over seven metres.
At the heart of the colony lies the key to their survival. A fungus.
But this isn't sloppy house-keeping.
This is a fungus that is found nowhere else on earth.
And the ants cultivate it assiduously.
The big-jawed ants chop up the grass covering it with an
antibiotic saliva that kills every kind of fungus except this one.
The ants are farmers.
They feed the grass to the fungus
and the fungus thrives.
The ants cultivate dozens of these fungus gardens throughout the colony.
This is what they eat.
The system is so efficient that a single colony can have five million members.
But the fungus is also dangerous.
As it grows it releases carbon dioxide that could asphyxiate the entire colony.
The ants' way of dealing with this danger is ingenious.
They construct their nest so that it has an automatic air-conditioning system.
The outer surface is so shaped that the slightest breeze
sucks out stale air through these central vents.
At the same time, fresh air is drawn down through the outer vents,
right into the heart of the nest.
Our own societies have existed for thousands of years
but insect societies have lasted for millions.
There may be ten million different kinds of insects
and there are 200 million individuals for every one of us.
The insects' flexible armour and their adaptability
has made them the most abundant and the most diverse animal group in our planet's history.
The Sierra Madre Mountains in Mexico
are home to one of the greatest natural wonders.
A billion bright orange butterflies offered the Life team a wonderful filming challenge.
The colonies are only found above 3,000 metres
and the team trek there slowly in the thin air.
The monarch phenomenon was only discovered here around 30 years ago and one man has been studying
them every year since, Professor Lincoln Brower.
His knowledge will be essential if the team are to achieve their goal
of flying a camera among the butterflies.
It's amazing that the butterflies only come to this area
that's about 30 by 60 miles in extent.
There are other areas that have high forests,
in different parts of Mexico, to the west of here, to the south of here,
but as far as we know, this is the only place that monarchs are able to spend the winter.
The butterflies are in such numbers that filming them the traditional way,
from a camera on a tripod, is reasonably straightforward.
But to get a butterfly's viewpoint by flying a camera amongst
the swarms is going to be altogether more difficult.
First, the team need a spot where butterflies gather in huge numbers.
Luckily, Lincoln knows a place where thousands come down to drink every day.
The crew spend the next three days preparing the equipment -
a remote-controlled camera, a lot of cable, two bicycle wheels, a bag of rocks and some muscle-power.
Now all they need to do is wait until the butterfly numbers reach truly impressive proportions.
By mid-day, the butterflies are swarming
and it's time for the camera to glide with them through the air.
Three and away.
Superb. OK, let's just stop that.
Absolutely stunning.
We've got great numbers coming in. Let's keep going
and then we'll do a turn round shot.
A series of unique shots flying with the butterflies.
But that was the easy part.
Now it's time to get the camera 50 metres up into the tree tops.
Filming the roosting butterflies is not going to be simple, the clusters are unstable.
And they can suddenly disperse without warning,
what Lincoln calls an explosion!
Here's another explosion. Wow, look at that!
And they're going right over our head.
Spectacular, no doubt, but a real problem for the climbing team, Jim Spickler and Tim Fogg.
Would it be better for us to start now?
we're gonna be very careful not to disturb them,
or limit our disturbance, but if we do disturb them right now
it seems that they're warm enough that they could relocate to a cluster right adjacent to them,
do you think that's true?
Well, if you disturb them they tend to fly away from the tree, 50 feet or so,
so you'll lose those clusters I think if you disturb them.
Do you think they'll cluster again though, tomorrow night? I doubt it.
< I think they'll just move down.
That's really hard stuff, you know because I can't see how we can get up the trees
and do what we have to up there,
close to any clusters without them flying.
I just don't know how I'm gonna be able to get an arrow into the tree.
I think if you picked your tree, you could put the arrow in it now.
The prospect of rigging cables high in the canopy, without disturbing
the butterflies is a daunting one. They may only get one chance.
One false move and it'll all be gone.
I had the impression that they might come back but
Lincoln says they just won't, they'll just move on to another tree.
So we put all the rigging in, disturb them and then...
that's it!
Choosing which trees to rig is a critical decision.
Can you get right to tree number six do you think, or is that too far?
They begin by firing a line over a suitably high branch.
That'll work.
Nobody, not even Lincoln, knows how the butterflies will react.
Yeah that's gonna work perfect, I think.
OK, great.
I've got to do a changeover here so just give me a moment.
There's an explosion.
Thankfully, it's not in the trees that Jim and Tim are rigging with such care.
Can you just push it towards me a bit?
Ouch. You OK?
Yep. OK, get your fingers out.
OK, that's good.
It takes another three days to get the aerial rig set up, followed by many hours of fine tuning.
Just pan it so we don't see it in the monitor, please.
Everything is finally set and the butterflies are still there.
One, two, three.
Take one.
Too slow.
There was no load at the beginning
and then suddenly it just completely stopped.
Take six.
Keep going. Start to slow, slow and keep going, keep going, keep going.
OK, Mike, hold it.
Not far enough.
We've not got enough weight, Jim.
Take nine.
Go on, Mike.
Go on, Mike. Get in close, Mike, now start slowing.
OK.
It's still not right and now time is running out.
I think the light's going.
Shall we do one last take?
All right. Because these ones here, we're losing the light on them.
Try and get a shot that's going past here if it's smooth.
One, two, three, and we're away.
Take 17.
And it's looking good.
OK, start slowing, Mike. OK, keep it going, keep it going.
Success at last.
With the technique now working, the crew rig more and more shots
to give an aerial perspective on the monarch phenomenon.
His work advising the crew over, Lincoln continues the observations
he's been making for over a quarter of a century.
Although the butterflies are still here in immense numbers,
he's worried there is a threat to their survival.
The big, huge influx, maybe sometimes as many as two billion butterflies,
flying down into this tiny area of 30 by 60 miles,
is thoroughly endangered by illegal logging.
If the forest is not protected the phenomenon will be lost.
It'd be a disaster.
I mean, it would be like taking the Mona Lisa out of the Parisian museum and,
and burning it up.
Subtitles by Red Bee Media Ltd
E-mail subtitling@bbc.co.uk