Original subtitles

When winter descends upon Europe,

many animals have no choice but to leave.

(majestic music)

The migrations of many discrete creatures

have been a mystery until now.

And yet they cross oceans and deserts,

brave intense weather,

and travel thousands of kilometers unabated.

Thanks to recent scientific progress,

we are finally able to follow their journey

and discover the secrets behind their incredible migrations.

(upbeat music)

The painted lady hides its secrets well.

Untraceable in winter, this butterfly reappears each spring

as if by magic.

Behind this mystery lies an extraordinary story.

The re-conquest of an entire continent

by an insect that weighs less than a gram.

(speaking in foreign language)

How does the tireless painted lady manage to fly for hours?

To orient itself confidently, and to reach altitudes

of over 1,000 meters?

To find out we're going to accompany this creature

on its incredible journey from Morocco to the Arctic Circle.

(gentle music)

The painted lady's journey begins far from Europe,

on the other side of the Mediterranean in Southern Morocco.

In early April and south of Marrakesh, spring came early.

Temperatures averaged 24 degrees

and numerous plants are already flowering.

Oh there is some larva but--

Constanti Stefanescu,

a researcher at the Granollers Museum of Natural Sciences

in Catalonia has studied the painted lady for 20 years.

Now, like every year,

he combs Southern Morocco's grassy hills

in search of butterflies.

The difficulty of finding painted ladies

depends very much on the season.

(flighty music)

There are some years where the butterfly is extremely common

and then for example here in Morocco,

you can find it everywhere

and some years where the butterfly is really scarce.

(contemplative music)

In a country like this that is so big

the chances of finding things are tiny.

(contemplative music)

Well this is a very fresh butterfly.

It probably emerged today or yesterday.

He's a very new one

and it was feeding on lavender

which is one of the preferred nectar sources.

I guess this butterfly will start migrating

as the conditions are good for it.

(wind whispering) (gentle music)

Butterflies are remarkable creatures

whose body temperatures change

in relation to their surrounding environment.

They need a lot of sunshine to stay warm.

It's common to see butterflies still numb

from the evening cold warming themselves in the morning sun.

(gentle music)

If the temperature does not reach minimum

which is about 35 degrees or even more in some species

butterflies cannot move.

One of the first things that they do

is to search for nectar

because the nectar is rich in energy.

(bright music)

Found in all the Maghreb countries from September to April

the painted ladies enjoy a mild winter and lush ecosystems

that are favorable to the particular types of plants

they need to reproduce.

After warming themselves and boosting their energy,

recently hatched painted ladies

immediately set about fulfilling their primary mission,

to reproduce. (cattle lowing)

In the afternoon the males go to the hilltops

to establish territories and to defend them

against other males waiting for females to come and mate.

(dynamic music)

You can see that the males have very speedy flight.

They interact between them, they make acrobatic flights

that last sometimes several minutes.

They just come here because this place can be seen

from the distance.

At the moment you can see from here

that the everything is green.

There are flowers, there are the host plants

that are needed by the females to lay the eggs

but probably in two weeks or three weeks at the most

all this will become withered, will become--

Hi.

Yellow and dry and so the opportunities

for the painted ladies will diminish dramatically

in three weeks.

Migrating is the only option.

Oh, see.

Okay, here is again.

Migration is common behavior for birds

but surprisingly it also pertains to certain insects.

We know today that a small number of dragonflies

and butterflies are capable of undertaking journeys

that are thousands of kilometers long

in search of more favorable environments.

(contemplative music)

How do these migrating creatures know when it's time

to begin their journey?

Many factors can influence the moment of migration.

Excessive temperatures or precipitation,

the number of hours of daylight,

a reduction in the amount of food supply

or any combination thereof.

But migration can be triggered by other causes.

For the painted lady,

the presence of parasites attacking its caterpillars

is a deciding factor.

The main enemy of this butterfly

is a tiny wasp, is a parasitic wasp

that lay the eggs inside the body of the caterpillar.

Then when the eggs emerge, the larvae of the wasp

start to eat the body of the caterpillar from inside.

When they complete the development

they kill the larva and they emerge as adult wasp

that start to search for another caterpillar

and repeat the process.

At the end of the winter sometimes

more than 50% of the caterpillars die because of that.

(dramatic music)

The butterfly that have survive for them

it's much better to leave the country

and to colonize a new area which is at the moment

free of these parasites.

(contemplative music)

The butterflies that emerge in April

know that the survival of their species

depends on a rapid departure.

The proliferation of parasitic wasps,

rising temperatures, and local drought

could prove to be fatal.

(sheep bleating)

(contemplative music)

Constanti meets with one of his colleagues

who's taking a census of Southern Morocco's butterflies.

The team has gathered

because the painted ladies' migration is imminent.

(contemplative music)

There's a cocoon here.

Come see.

There's a cocoon here I said.

Oh yeah, over here.

Let me see.

(speaking in foreign language)

A cocoon and an A5 type caterpillar.

We're lucky.

How long will it take?

The caterpillar should make its cocoon tomorrow I think.

And this cocoon has three or days left at the most.

This is one species of thistle of the genus Carduus

and is one of the most common host-plants that are used

here in Morocco and also in Spain.

In places like this that there are so many of these plants

sometimes there are important emergences

of many butterflies.

(playful music)

(speaking in foreign language)

Look, there it is.

Got it!

Great!

Well done my friend.

According to our censuses that have been done

in the last years now is the timing

when migration starts

so last days we were in the south

and there were no butterflies at all

because most of them had already left to Europe.

(speaking in foreign language)

Here they are emerging right now

but probably in one, two weeks

there will no longer be butterflies

because these too will start the migration to Europe.

(bright music)

Some butterflies are more willing to migrate than others.

Hey!

This one for example was a female that was egg-laying.

This one probably will not migrate

and will stay here laying all the eggs before she dies.

In fact there is like conflict between migration

and reproduction.

Butterfly that is migrating has to invest

all its energy in migration.

A butterfly that is breeding has to invest all its energy

in breeding so when butterflies migrate

they do it in theory before they reproduce

and then when they arrive to the destiny

they feed on nectar, they get energy,

and then they start the breeding period.

(bright music)

There's two of them interacting.

Look, look!

It's lasting a long time.

I don't see them.

They're over here.

That's pre-migration behavior, look.

The butterflies have engaged

in a strange frantic chase in the last few days.

This disorderly agitation is instinctive behavior

that seems to stimulate the butterflies' desire

to begin their migration.

The main difference between the migration

of birds for example and that for the painted lady

and other insects is that the migration of butterflies

as exemplified by the painted lady

is a multiple generation migration.

This means that every generation makes a part

of the complex sequence so our butterflies that are emerging

here in Morocco will fly to Spain, to the South of France,

will breed there.

They will die and the offspring of these butterflies

when they emerge will continue to migrating to the north.

Each leg of the migration represents these 10s of

about one thousand kilometers more or less.

(bright music)

Over the course of several weeks

waves of hundreds of thousands of butterflies

make their move from Northern Africa

towards the European continent.

Europe offers the butterflies cooler temperatures

and ecosystems that are in full-spring bloom.

Painted ladies coming from the Eastern Maghreb

don't hesitate to take on the Mediterranean

which they sometimes cross in a single attempt,

carried by favorable winds.

Butterflies born in the west may be a bit less bold

and some choose to cross at the easiest passage,

the Strait of Gibraltar.

(dynamic music)

For the painted lady, the strait is no major obstacle.

This famous rock which marks the entry point to Europe

is only 15 kilometers away

on the other shore of the Mediterranean.

Only three days after their departure from Africa,

the first butterflies have already reached Northern Spain

and Catalonia.

The protected Garrotxa Volcanic Zone Natural Park

is an ideal environment for the butterflies

to rest and recuperate as they replenish their energy.

The painted ladies

have already traveled over 1,000 kilometers,

despite their flight appearing hesitant or random.

That impression is certainly deceiving.

This tireless butterfly actually flies very efficiently.

The painted lady flies using four wings that are powered

by extremely strong chest muscles.

The butterfly which only weighs a quarter of a gram

has a full wingspan of 5-7 centimeters.

These four large wings beat about 20 times per second,

giving this ultralight insect the gift

of highly effective flight.

The wings are made of a transparent membrane

that's covered with miniature scales

forming colored patterns that change depending on the side.

There could be up to 600 scales per square millimeter,

overlaying each other like tiles on a roof.

These scales are hollow

which gives them a large surface area

that's both light and resistant.

These characteristics also mean that the scales

can quickly accumulate the heat that's essential

to the butterfly as it flies.

Despite its fragile appearance,

this insect is a very robust

high performance flying machine.

(dramatic music)

London's Royal Veterinary College is home to a team

that specializes in studying animal flight.

Richard Bomphrey and Masateru Maeda

developed a tool that can be use to analyze

how butterflies fly.

I'm just feeding him or her,

just started and looking good.

Yeah, they're looking healthy and well.

Yeah.

One of the tools that we have here

and the one we're gonna use today

is this small-scale wind tunnel.

Now we built it ourselves, switch it on over here.

When you switch that on, power gets delivered

to these four fans here.

And then it moves along and it passes through a gauze.

So the honeycomb is to straighten the flow

and the gauze is to equalize the pressure

across the cross-section of the wind tunnel.

When it gets accelerated by the contraction cone

it comes out this end beautifully laminar,

smooth, coherent jet and this is the environment

just next to the outlet where we can fly animals

and visualize the flow patterns that they're making.

To visualize the flow what we do

is using this Nichrome wire,

which is like a fuse wire,

and when you pass current through it it gets hot.

And what we do is dribble oil

which we dribble down it like this

and when we turn the power on if you could do that Masi

what you'll see is the smoke comes through.

Can see the smoke bending around my finger.

Strings glued to the butterfly's back

hold it in place.

Okay, time to turn the wind tunnel on.

The procedure is painless

and the strings will be removed after the experiment.

I think we can do better than that one

I should think so-- Yeah.

Am I in the right place now?

Slightly forward.

Yes, exactly.

Okay? Okay.

Three, two, one.

(beeping)

(contemplative music)

Let's go and have a look 'round here.

Well it's taking it out of the lights this time.

Yeah, good idea.

Beautiful. Yeah, actually nice.

The first thing that you notice is that

these streaks at the top turn downwards

and they get thrown down.

That process generates a lower pressure above the wing

and a higher pressure beneath the wing

and the result of that is it accelerates air downwards

and by Newton's Third Law,

if you accelerate something downwards

you experience the acceleration, the reaction upwards

and that's how the butterfly is generating its lift.

In fact, when it wants to accelerate up,

what it will do is increase the amplitude of the stroke

so instead of flapping like this

it will almost clap the wings together

and sometimes does clap the wings together

at the top and bottom of the stroke

so that's how they would go up

and when they're settled into their long-distance migrations

they might choose to reduce that amplitude

when they're in fast forward flight

which can save them some energy.

(contemplative music)

The painted lady's flight technique

is incredibly energy efficient

which means this little insect

has exceptionally high endurance.

It can flap its wings for many hours at a time,

all the while traveling at an average speed

of 20 kilometers per hour.

(contemplative music)

Having arrived from Morocco five days ago,

the butterflies have had time to recuperate

and are now eager to resume their frantic journey.

Ahead lies a seemingly insurmountable obstacle,

the Pyrenees Mountain Range

which separates Spain from the rest of Europe.

How will these frail travelers tackle

this mountainous wall of rock over 400 kilometers long

and thousands of meters high?

Most painted ladies will avoid it all together.

They head towards the passage where it's easiest

to cross the Pyrenees Mountain Range.

Some travel east along the coast of the Mediterranean

while others travel west by following the Atlantic coast.

(contemplative music)

(train whirring)

The painted ladies' itinerary often coincides

with the main routes built by mankind for travel

or communication purposes.

Over hilltops, through deep valleys dug by rivers,

and along coastlines, these natural itineraries

are used by butterflies and men alike.

One of the butterflies most studied migratory pathways

follows the Atlantic coastline through France.

It is difficult to predict when the butterflies will arrive

but some people know with great certainty

where they will appear.

Yves Lanceau and Nathalie Truchet,

two naturalist passionate

about the painted ladies' migration

are often waiting for them.

They only capture butterflies to admire them.

Look there, I'm going to try to catch it.

Lets see.

Is it a cabbage white or a green-veined white?

Look.

It's an enormous cabbage white.

Those black spots mean it's a female.

Shall we release her?

Go on.

Don't move too much.

There, bye.

(playful music)

I see flying over there.

That's a nice area.

Yes with lots of flowers.

Excellent.

That's a painted lady, right?

Yes, that's a painted lady.

And I missed it, I missed the painted lady.

(bright music)

Migrations take place through these migratory corridors

which are not very big,

usually 50 or 100 meters wide.

If we wait perpendicular to the corridor,

we can actually count how many butterflies are going by.

Usually there's a few each minute.

Sometimes as many as one or two every second.

(contemplative music)

There, I got it, yes.

The colors fade from brown to orange with hints of red.

(speaking in foreign language)

They travel thousands of kilometers

and even though this one was probably born here

its mother is most likely from Morocco.

It will presumably continue north

which is really amazing.

(playful music)

The painted ladies

that have completed the first part of their migration

now begin to reproduce.

It's the second generation butterflies

that will continue the journey.

This clever strategy means the butterflies recolonize

every European country they cross.

Here, the parasitic wasps are rare and food abundant.

The conditions are perfect for reproduction.

A brief nuptial parade precedes mating

between the male and female facing away from each other.

(contemplative music)

As soon as her eggs are fertilized the female flies away

to find a good plant where she can lay them.

She carefully chooses the habitat

for her future caterpillars.

The egg is minuscule, barely over one millimeter.

Laid on the upper side of a leaf,

the egg is very vulnerable.

It often falls victim to predators like this bug larva

which can drain the egg in a single sip.

(dramatic music)

The rare survivors only need a few days to hatch.

(playful music)

The tiny caterpillar that emerges

quickly begins searching for food.

Caterpillars have voracious appetites

that drive consumption of as much food

in as little time as possible.

When the caterpillar's skin becomes too tight,

it molts.

It sheds its skin four times

before entering the pupal stage.

(contemplative music)

In just 10 days the caterpillar quadruples in size

and totally changes appearance.

(wings flittering)

Extremely vulnerable, it builds a shelter

by folding a leaf over itself

and attaching it with silk threads produced by its mouth.

This disguise keeps it sheltered

from predators and the rain.

(pensive music)

After two weeks of frantic fattening,

the caterpillar has enough reserves

to pass through the last stage of its metamorphosis,

the cocoon.

(bright music)

40 days has passed since the eggs hatched.

Metamorphosis is a long and complicated process.

(gentle music)

When the butterfly emerges from its cocoon,

its wings are damp and seem smaller than its body.

They require about an hour to unfold

and take on the definitive shape.

Before making its first flight,

the young butterfly enjoys a moment in the sun's warmth

to complete the process of drying its wings.

(gentle music)

Oh you're beautiful,

yes, you're beautiful.

Very beautiful.

Freshly hatched,

the second generation of painted ladies

are now ready to pick up where their parents left off

and carry on their northerly migration.

(pensive music)

When they run into an obstacle,

they're so fixated on their destination

that they simply go over it.

Whether it's a house or trees,

they won't go around, but straight over it.

They're obsessed with their direction.

They're better at it than we are.

We can barely go anywhere without a GPS.

They have an internal GPS.

(contemplative music)

It is now mid June

and the migration began over six weeks ago.

Some recently hatched butterflies

take flight almost immediately,

flying over the sea without hesitation.

Their flight plan is ingrained in their genes

and drives them towards a surprising destination.

Southern England where plants are in full bloom.

Butterflies are not the only migratory animals

that instinctively know how to orient themselves

but it is incredible that such small creatures

can rival the precision of other more evolved ones

like birds.

(bright music)

How can an insect with a brain as small as the painted lady

instinctively maintain its direction

as it flies during migration?

(contemplative music)

Rebecca Nesbit long studied this question

through her doctoral dissertation.

Assisted by Jason Lim from Rothamsted Research,

she uses an ingenious device to gain insight

into how butterflies orient themselves.

The device must be placed in a very sunny area.

(dynamic music)

A painted lady which will be released after the experiment

is attached to a pivoting stick that records the direction

of its flight.

Unable to see the landscape around it,

the insect flies in place.

Okay, she's flying.

(playful music)

So we know the direction of the butterfly's body

and as it turns we are recording that.

Every time it turns we've a got a new bit of data

coming into the computer

and that allows us to plot out that flight path.

Okay, and I'm going to three, two, one and let go.

Its rotating? How's it looking?

Yes, Yes. Looking good.

From this we're able to tell

what direction the butterflies are heading in

and that means we can look at the directions

of the whole group of butterflies and see whether

they are flying in a favorite direction.

I can see.

Yes, it's moving north, northeast, east something, yeah.

And now stable, yes, yes.

If I move the direction of the butterfly

to a different location

when released the butterfly will tend to go

back to the original location that he wants to fly to.

(contemplative music)

With the sky as the only reference

it seems as though the butterfly uses the sun

to orient itself.

To test their hypothesis Rebecca and Jason

prevent the insect from seeing any of its surroundings.

We put an opaque lid on the top of the simulator

blocking the sky from view

and that allows us to tell whether butterflies

are still able to maintain their migratory direction

when they can't see the sun

and what we found was that the butterflies

are not able to maintain that preferred direction

when they can't see the sky.

(dramatic music)

The experiment proves

that the painted lady orients itself in relation

to the sun's position.

The painted ladies migration is a phenomenon,

the scale of which can be lost on us.

They migrate en masse but often pass by unseen.

In order to observe them we have to use tools

like a radar.

And now we can open that yes, very good.

Okay, the antenna looks okay so I'm going to go in

and turn on the radar and see how it goes.

(pensive music)

(machine buzzing)

The radar works, operate from 200 meters

to 1.2 kilometers above the ground

and it's actually measuring a very small columns of air.

If you look, imagine your lights going up

so at one kilometers above ground,

so we're looking at 30 meters in diameter

so it's really a very small columns of air we are sampling.

The entomological radar

generates an electromagnetic wave above it

that detects altitude, flight direction,

and the number of butterflies passing

during a specific time-frame.

Extrapolated to the sky as a whole

the radar collected data reveals the true scope

of the painted ladies' migration.

These four diagrams on the right

are data for butterflies and at the top

we have the spring, this is data from April, May, and June.

Each dot represents a single day and the track,

this is the direction the butterflies were traveling in,

the heading, this is the direction

that the butterflies were facing in

and what you can see is as we would expect.

In the spring they are on a northwards migration

moving into Northern Europe

and it was only with the invention of techniques

such as this radar that we were able to monitor this.

(pensive music)

Using the radar also helps scientists

discover that certain years boast much greater numbers

of migrating painted ladies than others.

(dynamic music)

2009 was a record year with millions of butterflies

being observed throughout Europe.

This mysterious massive migration

only takes place once or twice a decade

and scientist still cannot fully explain it.

(dynamic music)

The radar-based study of this spectacular migration

also helped another British scientist, Jason Chapman,

better understand the role of the wind

in the painted ladies' migration.

It seems the butterflies that they fly up

and sample the winds and if it's a favorable direction

and it's fast then they will tend to stay at those height

and that's going to travel, help them travel

a very long distance in a short amount of time

but there's a lot of variation

so we don't have all the butterflies at one height,

there are some go very high, some stay lower down.

So there seems to be a lot of in-built variation

amongst the butterflies.

It's almost as if they are increasing their chances

of some of them survivin' by scattering themselves

over a range of different flight altitudes.

(dynamic music)

If the painted ladies' migration

often goes unnoticed, it's because it takes place

through several superimposed aerial corridors

ranging from the ground to over 1,000 meters in altitude.

It's now end of June.

Encouraged by excellent climatic conditions

and a large number of ideal host plants for egg laying,

the majority butterflies arriving in England

will stay to reproduce.

Other butterflies decide to travel onwards,

crossing the North Sea as they merge with other migrators

from all over the continent.

Carried by favorable winds

the butterflies continue their journey north.

They fly over Belgium, the Netherlands, and Germany.

(ominous music)

Yet, even in the summer, the journey isn't always easy.

Sometimes the weather takes a turn for the worse.

(ominous music)

Without the sun to orient themselves

and bombarded by heavy rain,

the painted ladies have no choice

but to momentarily interrupt their traveling.

But it takes more than that to discourage the brave

painted ladies.

As soon as the sun reappears the journey continues.

After a few more days they will reach their destination,

Sweden.

In early July the Scandinavian summer

is particularly favorable to the painted lady.

The days are long and full of sunshine,

creating plenty of ideal ecosystems for insect reproduction.

(contemplative music)

Just east of Sweden on the island of Gotland

biologist Lars Pettersson is conducting

his annual butterfly census.

Many painted ladies end their migration here.

I caught a migrant painted lady.

It has traveled quite far and you can see from the,

still wants to move away, you can see from the pattern

that it has been on its way for quite some time.

One can easily distinguish

a migratory butterfly by observing the state of its wings.

The wings of a painted lady

that has traveled 1,000 kilometers have lost a lot of scales

and their edges are irregular

while the wings of a freshly hatched butterfly are perfect.

(flittering)

Here we have a couple really fresh ones

and they're much nicer looking than the one

that had flown a long way

so this one's probably hatched near here

and haven't flown very long.

(bright music)

I will always see that there are many more butterflies

in autumn and late summer than what we have in spring.

That's because the painted lady migrates here in spring

and in July you have new hatchlings

and they are much more numerous than the ones

that are coming in from the south.

(contemplative music)

Just 10 years ago scientists thought

the butterflies migration ended on the island of Gotland.

But the extraordinary migration of 2009

allowed researchers to see that not all painted ladies

end their journey in Sweden.

That year, there were massive arrivals of butterflies

in Norway, Finland, and even as far as the Arctic Circle.

That is the farthest the painted ladies are know to migrate.

Any further north would be too cold for them.

In a few weeks the temperature in Scandinavia

will start to drop

and the butterflies will have no choice

but to leave again or die.

Much about the return migration remains a mystery.

There was a long-standin' mystery about the migration

of painted lady because there was an absence of observations

of return migrations in the autumn

so the there were two idea,

one was that the migrations were going on somehow

and we were not able to see them for some reason

or the other idea was that the autumn generation

would hatch out and then just die out

when the cold weather came.

So we decided to look in the U.K usin' our radar data.

These plots here show the distribution of

the painted ladies detected by the radars in England

at different heights above the ground.

There is an interesting difference between

the spring and the autumn.

If we look at the spring data on the top,

we see a gradual decline from the very high altitudes

which continues down to the lowest

and that suggest there are many, many painted ladies

flying close to the ground

and only a small number flying at higher altitudes.

Interestingly in the autumn we don't see that pattern

so we see the painted lady butterflies concentrated

at greater altitudes, around about 4-500 meters

above the ground.

So radar told us that actually millions were migrating

high above out head totally invisible.

(contemplative music)

During the autumn conditions deteriorate

so they have to get all the way back down

to the Mediterranean or perhaps even North Africa

in a single adult lifespan.

So that doesn't give them very long

so they have to travel very fast

in order to make that migration

and their only way to do that

is to fly on those high-altitude winds.

(contemplative music)

For Scandinavian butterflies

high-altitude winds are powerful air corridors

capable of carrying them south in record time.

Yet, many of them never make it to their final destination.

(dramatic music)

Whether coming or going, danger is everywhere.

Many butterflies won't survive the journey.

Only the hardiest painted ladies will make it

to their destination.

After traveling for only two weeks

the butterflies converge massively

and head towards the Mediterranean.

In Morocco in autumn

the prairies are still covered in flowers.

This is where the painted ladies will stay until April.

(contemplative music)

Constanti Stefanescu is awaiting them.

He chose to return as well

so he could continue his research.

(contemplative music)

I came to this field to catch some butterflies

that will be used for isotope analysis.

The isotope is one form of one chemical element

so it each chemical element has different forms

depending on a number of neutrons on the nuclei.

(playful music)

So far we are focusing on the deuterium

which is the isotope of hydrogen.

When the caterpillar eats a particular plant

like mallow or thistle the percentage

of the deuterium that was on the plant

passes through the wings and through other tissues

of the butterfly so when we analyze the wings

we know what was the percentage of the plant

so in that way we know the place where the caterpillar

grew and where the butterfly emerge.

For example, as you move to the north

the quantity of deuterium increases.

The wings, which the scientist removes

from dead butterflies contain precious information

about their origins.

The initial results from this study

meet the researchers' expectations.

We have been analyzing isotopes for the last two years

but we are still doing some work.

For example one of the most exciting findings

was that some of the butterflies that we collect in Morocco

also come from south of the Sahara.

That was quite an unexpected result

and what it says is that the

migratory system of the painted lady is huge

because it encompasses not only Europe and North Africa

but also the Sahara region.

So it's a very complex system that can

represent distances of 5,000, 6,000 kilometers

which is the longest distance for a migratory insect

that has ever been described.

(bright music)

Painted lady butterflies

accomplish an incredible feat.

Stage by stage, generation after generation,

these tenacious butterflies travel thousands of kilometers

for their circular migration between Africa and Europe.

(bright music)

Only winter gives pause for a few months

to these incredible insects and their great journey.

But come the new year when it will be too warm in the south,

the painted ladies will take to the road again

like they've been doing for thousands of years.

(bright music)