Dragons & Damsels (2019) - full transcript

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(dramatic music)

Dragonflies and damselflies
have been around

for a very, very long time.

They watched our ancestors
crawl out of the water

and witnessed the rise
and fall of the dinosaurs.

They've flown over lakes and rivers

for the last 330 million years.

What is the secret of their
extraordinary success?

Perhaps it is because they're completely

at home in two worlds.

Below the surface their
larvae are deadly hunters.



And when they've eaten their fill

and grown to full size,
they crawl out of the lake,

change their shape and take to the air.

(body crinkling)

But that's only part of this story.

The real reason for their long reign

over Planet Earth can be
found in their daily lives,

in behavior as complex as that
of many birds and mammals,

yet normally unseen.

So let's spend the summer

by this particular lake and watch closely.

The little creatures really
do have the biggest stories

to tell in the world
of dragons and damsels.

(wings fluttering)



(water trickling)
(birds chirping)

(gentle music)

Late spring, and with the warming sun,

the lake is getting busy.

The reeds are alive with
dragonflies and damselflies.

A miniature soap opera is about to start.

And one if its brightest
stars is a little damselfly

with a big role to play
in the coming drama.

The common blue.

(pencil scraping)

(birds chirping)
(wings fluttering)

Common blues are both
very common and very blue.

(gentle music)

A color so intense it seems to
glow when it catches the sun.

And in the world of dragons and damsels,

common blues are real characters.

Damselflies are smaller and
daintier than dragonflies

but they have an attitude
way bigger than their size.

Common blues are always bickering

over the best lakeside viewpoints.

And their huge bulging
eyes enable them to hide

behind a single blade of grass

and still keep watch on the neighborhood.

A picture of peace and serenity.

But to survive here, a damselfly is going

to need more than those sharp eyes.

It needs equally sharp wits.

They may have brains less
than the size of a pinhead,

yet common blues lead a
surprisingly complex life.

(birds chirping)

Females are not such a brilliant blue,

but when one of them visits the
lake, she soon gets noticed.

There's no romance,
a male simply pounces on her

and with no ceremony, hooks up.

And this one has mated, just.

There's stiff competition
for any single lady.

And she doesn't stay single for long.

He clamps himself to her thorax

with claspers at the
very end of his abdomen.

So far, so good.

But now he has a problem.

His reproductive organs open
at the end of his abdomen

and so do hers.

So in this position,
he can't actually mate with her.

But he also has a second
set of reproductive organs.

A kind of holding pouch,
halfway up his body,

that he's already filled with sperm

from the main sex organs
at the tip of his tail.

But it will take some extraordinary agility

for the pair to consummate this union.

(gentle music)

The female now has to
swing her abdomen forward,

so that she can reach
up to collect the sperm

from his secondary organs.

And he tries to help her as much as he can.

There we are.

Now together, the mating couple
form a romantic heart shape.

But there's a ruthless
side to this tender moment.

(dramatic music)

The male's secondary sex organs are

not only storage pouches,

they also contain a device
unique to dragons and damsels.

(dramatic music)

It's a probe with two hooks on the end.

With this, he's able to scoop out any sperm

that she may have acquired
from her previous mating.

And so ensure that he will
be the father of her young.

And now, the male needs
her to lay her eggs quickly

before another male comes
along and scoops out his sperm.

He tries to lift off with
the female still attached.

But she seems reluctant to leave,

even with the male at full throttle.

(upbeat music)
(wings fluttering)

He tries to persuade her with
a sharp bite to the head.

But no, she's clearly not impressed

by him or his pickup technique.

And there are plenty of other males around.

All she has to do is to wait.

Here's another male.

(wings fluttering)

She nips her first partner's tail

and after all his effort, he gives up.

And she flies off with her new partner.

Males will jump on any female they spot.

But females are much more choosy.

Her former partner's sperm is scooped out

and the new couple fly off
together to lay their eggs.

(wings fluttering)
(birds chirping)

Undaunted, our lonely male sets out

to look for a more willing partner.

But he can't afford to be too preoccupied

with the opposite sex.

(dramatic music)

He really needs to watch where he's going.

It just isn't his day.

The wasp spider has built
her lethal trap in the reeds,

in an excellent spot to
ambush unwary damselflies.

And she wraps her victim
in a shroud of silk

to stop him struggling.

And his short life is over.

(birds chirping)
(spider munching)

A large lake like this is home

to more than 20 different kinds

of dragonflies and damselflies.

But not all of them will
spend their whole lives here.

Both dragons and damsels
are great travelers.

Fly high and covering long distance

in their search for water.

Their eyes can detect
polarized light reflected

by water surface, so they can spot a pond

from a long way off,
no matter how tiny it is.

This lily pond in a garden
might be small compared

to the lake, but it's been discovered

by these intrepid explorers.

A tiny realm,
reigned over by an emperor dragonfly.

(pencil scratching)
(gentle music)

Dragonflies are more powerful and agile

in the air than damselflies

and they defend their own territories

around lakes and ponds,
engaging rivals in aerial dogfights.

But this intruder is a female,

and the male dragonfly
finally realizes this.

So he now grabs her and hooks up in midair.

Now they must perform the same
gymnastics as damselflies.

They can even fly up together like this.

But after mating,
they separate and the female goes off

to find somewhere to lay eggs on her own.

(wings fluttering)

She lays her eggs inside ponds,

but she's very choosy about
picking exactly the right place.

The carefully tended lilies

in this ornamental pond are just right.

(wings fluttering)

Sometimes, in her quest

to give her eggs the
best chance of survival,

she decides that the
perfect place is a long way

below the surface of the water.

But she doesn't mind getting wet.

(birds chirping)

A dragonfly can tell a lot
about both water quality

and the submerged vegetation from the way

that polarized light is
reflected from the surface.

So although the whole
pond looks the same to us,

discerning emperors quickly hone in

on the most suitable spots.

And one egg-laying female
soon attracts others.

(upbeat music)
(wings fluttering)

The egg-laying emperor is noticed

by the local common blues
that also use the pond.

But why?

Are they just curious about
these lumbering monsters?

Possibly.

But back on the big lake,

where there are vast swarms of common blues

this behavior seems to be
much more than just curiosity.

(wings fluttering)

As soon as the female emperor lands

on floating vegetation to lay her eggs,

she's surrounded by clouds of common blues,

buzzing her, mobbing her, harassing her.

Even landing on her and biting.

Eventually it all gets too much

for the female emperor and she gives up.

Why do the common blues risk

their lives chasing a dragonfly

that is much bigger than them
and could easily kill them?

Probably because of what those
emperor eggs will become.

(water gurgling)

(somber music)

Eggs hatch into larvae and
emperor larvae are killers.

(dramatic music)

Lethal predators.

Damselflies larvae are right up there

at the top of their menu.

Those sharp eyes spot any movement.

And the emperor larva stalks
its lunch like a tiny cat.

Its are eyes are huge.

And both face forward.

So the larvae has a stereo vision.

It can judge its distance
from a target very precisely.

And when it's close enough,

it deploys its secret weapon,

jaws that can shoot out
an additional half length

of its body,
a long-range strike capability that,

for the damselfly larva
comes out of nowhere.

(dramatic music)

The jaw snap shut and
the damselfly is impaled

on sharp spines,
to be hauled in and chopped up

by a pair of serrated blades
before being swallowed.

(dramatic music)

It's hardly surprising that emperors

and common blues don't get
along with one another.

(water gurgling)

But don't feel too sorry for the damsels.

They also are killers
and use the same tricks

as the bigger dragons,
just on smaller prey.

Water hog lice, slow moving, abundant,

the perfect meal for a
growing damselfly larva.

(gentle music)

And damselfly larvae are just as stealthy

as their bigger relatives.

Softly, softly,
just waiting for the hog louse to move.

(louse crunching)

(gentle music)

(dramatic music)

The battlefield under the surface

of a tranquil pond is no
place for the fainthearted.

And there's something else
lurking down here too.

Something hidden in the
dead leaves on the lake bed.

(dramatic music)

The larvae of darter dragonflies.

Squat creatures that look
like bits of dead plants.

They are ambush predators
and well camouflaged.

But these larvae have stopped hunting.

They are about to join the emperors

and common blues in the air above.

(gentle music)

And even the ugliest larva
turns into a beautiful dragon.

A common darter dragonfly,

as elegant and colorful as any emperor.

(gentle music)

(birds chirping)

Like emperors, darters defend
territories around the lake.

But they do this in a different way.

Male emperors sometimes take
a rest on a convenient perch

but they spend most of
their lives on the wing.

They patrol their territories in the air,

hawking up and down, occasionally hovering,

to survey their domain
and check for intruders.

(dramatic music)
(wings fluttering)

(birds chirping)

Darters are less energetic.

They find a convenient perch to keep watch,

and every now and then fly off
to check out their territory,

often coming back to the very same spot.

(wings fluttering)

Sometimes they pick the
flimsiest of perches.

But they have the poise
and balance of a ballerina.

All dragonflies are
true masters of the air.

They can hover, rock steady.

(dramatic music)

They can fly backwards.

And turn on a dime.

(upbeat music)

All these extreme aerobatics depend

on very sophisticated wings.

Wings that have corrugations for strength

and complex patterns of
veins that allow each wing

to change its flapping angle
independently in flight.

But exactly how do dragonflies
achieve their aerial skill?

Ready when you are

Yep.

At the Royal Veterinary College in London,

scientists are trying to find out.

Here Richard Bomphrey uses smoke trails

to reveal the complex patterns
of airflow over the wings.

(wings fluttering)
(gentle music)

(lights clicking)

And he studies the way
wings move by filming them

from every angle with
multiple high-speed cameras

which slow down the action 80 times.

Well, that's a very nice
take-off sequence of this darter.

We can see that the wings twist

and they bend and they change in camber,

each of the four wings is
being driven independently.

So sometimes the fore

and the hind wings are
flapping together in phase.

And after a little while,
it switches to counter stroking,

that's flapping out of phase.

Now we have nine cameras here.

And what all those views allow us to do is

to make a three-dimensional
model of the dragonfly's body

and the wings as they undergo
all these shape changes,

the bending and the twisting

so we can begin to understand

how the dragonfly controls its flight.

(gentle music)

If we now understand
how dragonflies achieve

such mastery of the air,
can we do any better?

(wings fluttering)

Scientist at Festo in
Esslingen, Germany, have tried.

A team of engineers here
spent many years trying

to build a robotic dragonfly

that mimics the dragonfly's natural flight

as Elias Knubben explains.

We tried to come as close

as possible to the real dragonfly.

We did a lot of research,

how do they adjust to
different surroundings,

how do they steer?

And I think we came quite
close to the functions.

We are able to control the
movements really precisely.

It has to be adjusted in
really very short times,

it's only milliseconds actually,

that you have time to react.

(wings fluttering)
(gentle music)

Festo's robo dragonfly can fly.

But it takes a skillful pilot,

controlling it remotely
just to keep it in the air,

let alone make it turn and twist

as elegantly as the real thing.

(gentle music)

The pilot has to control
nine different aspects

of the wings at the same time.

Far more complex than flying a helicopter.

Yet real dragonflies do this

with a brain the size of a pinhead.

This robot dragonfly is
an amazing achievement,

but it still doesn't come close

to matching a real dragonfly.

To be honest real nature
is even much better.

It's not really only, pretty much smaller.

But it's also,
it has even much more functions

and there's so much more to learn.

We're looking forward to do this.

(wings whirring)

But to be fair to Festo's engineers,

real dragonflies have been
practicing the art of flight

for 330 millions longer than they have.

And in that time, nature has come up

with more uses for wings than just flying.

(gentle music)

These particularly beautiful wings,

with deep blue patches,
belong to a banded damoiselle.

(pencil scratching)

Banded damoiselles avoid the busy lake.

They prefer flowing water
and live on a nearby river.

(birds chirping)

Unlike most damselflies,

banded damoiselle males occupy
small territories strung out

along the banks of the river.

And they defend them in style,

(gentle music)

by flicking their wings,
showing off their colors

and so signaling ownership

of their exclusive riverside property.

Not all banded damoiselles
are created equal.

The wing spots vary in size.

This can be hard for us humans to spot,

even comparing museum
specimens side by side.

But the difference are quickly picked out

by those sharp damselfly eyes.

(wings fluttering)
(gentle music)

The fittest males have the biggest spots.

An arrival with smaller
spots soon realizes his place

and gives in gracefully.

But if a male with similar size spots tries

to take over the territory,
a different strategy is needed.

A fight with an equal could be dangerous.

It's better to just behave like gentlemen.

So each male shows off his spots

with exaggerated wing beats,

until one of them finally
accepts defeat and retreats.

(wings fluttering)
(gentle music)

Often, other males from
neighboring territories join in,

and they all sort out

the neighborhood hierarchy
between themselves.

For an insect,
this is really sophisticated behavior.

Each male is able to decide
the best strategy to follow,

based on his estimation of
the toughness of a rival.

(train whistling)

(birds chirping)
(wheels clacking)

(gentle music)

Summer is now reaching its height.

(birds chirping)

And back on the big lake,

more and more dragons and
damsels crowd into the reeds.

(wings fluttering)

These are four spotted chaser dragonflies

and they gather in huge
roosts every evening

to wake at dawn ready to find somewhere

to claim as their territory.

Not easy when there are so many rivals.

(wings fluttering)

(birds chirping)

Space in the reeds is now at a premium.

But that's not a problem
for another species

of damselfly that has
now joined the throng.

The common red-eye.

(upbeat music)

Red-eyes perch on anything floating

on the surface, not matter how small.

Each a captain of its own little ship

as it drifts over the surface of the lake.

(birds chirping)

(wings fluttering)

But they also sometimes get unwitting help

from bigger residents of the lake.

The feather from a swan
makes an excellent raft.

(birds chirping)

And the red-eyes defend their little boats

against the ever inquisitive common blues.

A flick of the wings, a warning,

there's no more room on board.

(wings fluttering)
(birds chirping)

And there's not much
more space in the reeds,

now crowded with males, just hanging out,

waiting for a female to turn up.

(gentle music)

And when one does,
she turns a lot of heads.

(wings fluttering)

With the season in full swing,

there's a lot of desperate males around.

A female common blue
and she seems available.

But this is an azure
damselfly, trying it on.

He might look like a common blue,

but he's a totally different species

and he simply can't hook up.

Now a red-eye tries his luck.

This is definitely not going to work.

Finally a genuine common blue
and her patience is rewarded.

(wings fluttering)

In these crowded skies,
a male has only one mission.

To attach himself to a
female and stay attached.

It's the best way

to avoid another male
mating with his partner.

But it looks like hard work for the female.

Though her male does have his uses.

(wings fluttering)

To find the best spot to lay her eggs,

a female damsel must sometimes
submerge herself completely.

(dramatic music)

Being smaller than dragonflies,

she can get trapped by the
surface tension of the water.

The male, however,
stays dry above the surface.

And that can be important.

He may be needed to haul
her out of the water

if she gets into difficulties.

(wings fluttering)
(dramatic music)

But if the female gets too wet,

even the male's assistance
may not be enough.

Males don't like getting wet.

And if a female submerges
particularly deeply,

her mate just abandons her to her fate.

(water gurgling)

Now, she's on her own.

Without a male to help,

it's a real struggle to
clamber back out of the water.

As long as a male stays
attached to his partner,

no other male can steal her

and he can be sure that he will
be the father of those eggs.

But all these single
males don't just give up.

They constantly hassle egg-laying pairs.

And if a pair crashes onto the surface,

the male might drop his
mate before he gets soaked,

and then one of the single
males can grab the female.

(wings fluttering)

But this time,
they've picked an unusually feisty male.

He hangs on, even though he's now stuck

on the surface film himself.

They're so busy fighting over the female

they're getting careless

and all this activity
attracts the attention

of monsters from the deep.

(dramatic music)

(water splashing)

Trout snatch up anything
edible trapped on the surface.

This male has somehow
avoided becoming fish food.

But that was his good
luck used up for the day.

(dramatic music)

His struggles create ripples

and for the creatures that
live on the surface film,

that is like sounding a dinner bell.

(dramatic music)

Pond skaters can detect these vibrations

and pinpoint their source precisely.

(dramatic music)

Swarms of then hone in
on the helpless damsel.

(wings fluttering)

They pierce the damselfly's skin

with their sharp mouthparts,
inject a digestive toxin

and then suck up nutritious dragonfly soup.

(pond skater slurping)
(dramatic music)

(wing fluttering)

Great flotillas of pond skaters
patrol the lake's surface.

(flies buzzing)

And they're never short of food.

For the female damsels have

to settle there if
they're to lay their eggs.

But both dragons and damsels spend

as little time as
possible near the surface.

(wings fluttering)

Darters, however,
manage to lay their eggs in flight,

just touching the water briefly.

Darters do this as a pair,
a display of precision flying

that human engineers can only dream of.

(gentle music)

With each dip,
the female releases a few eggs.

Eight wings and two
brains working together.

The slightest miscalculation
would end in disaster.

Damselflies have a different strategy

to avoid the dangers of the lake.

Egg-laying pairs,
like these azure damselflies,

often gather in large numbers.

So there's less chance of
being the unlucky couple

if a predator does show up.

(flies buzzing)

(wings fluttering)

This male has sensed something is wrong

and is desperately trying to
pull his mate from the water.

But however much he
flaps, he can't take off.

(dramatic music)

And this is why.

An underwater predator,

attracted by the crowds
of busy damselflies,

has bitten off her abdomen
and made a meal of it.

Her mate is still trying to rescue her

and fly her to safety.

But it's too late.

(gentle music)
(wings fluttering)

The others carry on egg laying
as if nothing has happened,

paying no attention to the unlucky female

who just manages to haul
herself onto a lily leaf.

Always on the lookout for a single lady,

a common blue thinks he's
found an opportunity.

But soon realizes his mistake.

She is mortally injured and beyond rescue.

(somber music)

(thunder rumbling)

(gentle music)

For these tiny creatures,

raindrops are as dangerous as cannonballs.

(rain dripping)

Time to find shelter.

(thunder rumbling)

But the season is nearly
over and time is precious.

As soon as the sun returns,

male damoiselles are back
on their territories.

It's now almost autumn,
and while other damsels

and dragons are winding down,

one kind of damselfly
is just getting started.

An unusual species that's
attracted a lot of attention

in recent years, the willow emerald.

In the last few decades,

this species has moved
steadily north through Europe

and has even made the hop

across the North Sea and invaded England.

The British Dragonfly Society
have been keeping a keen eye

on the spread of these invaders,
as Fiona McKenna explains.

The willow emerald damselfly
arrived in roughly 2007 is

when we got the first record
of a female in the UK.

Their rapid invasion

of Northern Europe is a
consequence of climate change

which is why it's important

for scientists and naturalists
to chart its spread.

It's a marker that can tell us

how a warmer climate might
effect the natural world.

And the spread of the
willow emerald is easy

to track because of
their strange lifestyle.

It's quite unusual,
it's different to other damselflies.

You have to look up in trees for it.

Traditionally it's associated with willow,

hence it being called willow emerald.

But it has been known to utilize

other types of trees as well.

And it also lays its eggs into bark,

so it's got very unusual
egg-laying behavior.

(gentle music)

The female has sharp blades at the tip

of her abdomen which she uses

to cut holes in the bark of trees.

They leave very distinctive
little oval scars

where they've laid their eggs into.

The scarred branches are easy to see.

So you don't even need

to identify the damselflies themselves

to follow the species spread northwards.

Of all the dragons and damsels,

willow emeralds are among
the last to take to the wing.

And they must work quickly
before the frost arrives.

(gentle music)

Autumn brings the stories

of all dragonflies and
damselflies to a close.

Lakes and rivers seem deserted.

But not so.

Below the surface, the next generation,

the legacy of those frantic
matings of summer are waiting,

ready to take to the air
when the weather warms again

as they have done for the
last 330 million years.

(upbeat music)