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)