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(dramatic music)
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Dragonflies and damselflies have been around
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for a very, very long time.
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They watched our ancestors crawl out of the water
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and witnessed the rise and fall of the dinosaurs.
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They've flown over lakes and rivers
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for the last 330 million years.
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What is the secret of their extraordinary success?
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Perhaps it is because they're completely
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at home in two worlds.
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Below the surface their larvae are deadly hunters.
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And when they've eaten their fill
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and grown to full size, they crawl out of the lake,
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change their shape and take to the air.
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(body crinkling)
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But that's only part of this story.
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The real reason for their long reign
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over Planet Earth can be found in their daily lives,
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in behavior as complex as that of many birds and mammals,
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yet normally unseen.
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So let's spend the summer
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by this particular lake and watch closely.
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The little creatures really do have the biggest stories
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to tell in the world of dragons and damsels.
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(wings fluttering)
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(water trickling)
(birds chirping)
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(gentle music)
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Late spring, and with the warming sun,
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the lake is getting busy.
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The reeds are alive with dragonflies and damselflies.
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A miniature soap opera is about to start.
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And one if its brightest stars is a little damselfly
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with a big role to play in the coming drama.
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The common blue.
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(pencil scraping)
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(birds chirping)
(wings fluttering)
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Common blues are both very common and very blue.
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(gentle music)
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A color so intense it seems to glow when it catches the sun.
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And in the world of dragons and damsels,
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common blues are real characters.
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Damselflies are smaller and daintier than dragonflies
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but they have an attitude way bigger than their size.
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Common blues are always bickering
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over the best lakeside viewpoints.
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And their huge bulging eyes enable them to hide
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behind a single blade of grass
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and still keep watch on the neighborhood.
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A picture of peace and serenity.
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But to survive here, a damselfly is going
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to need more than those sharp eyes.
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It needs equally sharp wits.
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They may have brains less than the size of a pinhead,
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yet common blues lead a surprisingly complex life.
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(birds chirping)
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Females are not such a brilliant blue,
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but when one of them visits the lake, she soon gets noticed.
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There's no romance, a male simply pounces on her
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and with no ceremony, hooks up.
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And this one has mated, just.
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There's stiff competition for any single lady.
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And she doesn't stay single for long.
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He clamps himself to her thorax
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with claspers at the very end of his abdomen.
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So far, so good.
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But now he has a problem.
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His reproductive organs open at the end of his abdomen
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and so do hers.
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So in this position, he can't actually mate with her.
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But he also has a second set of reproductive organs.
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A kind of holding pouch, halfway up his body,
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that he's already filled with sperm
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from the main sex organs at the tip of his tail.
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But it will take some extraordinary agility
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for the pair to consummate this union.
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(gentle music)
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The female now has to swing her abdomen forward,
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so that she can reach up to collect the sperm
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from his secondary organs.
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And he tries to help her as much as he can.
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There we are.
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Now together, the mating couple form a romantic heart shape.
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But there's a ruthless side to this tender moment.
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(dramatic music)
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The male's secondary sex organs are
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not only storage pouches,
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they also contain a device unique to dragons and damsels.
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(dramatic music)
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It's a probe with two hooks on the end.
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With this, he's able to scoop out any sperm
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that she may have acquired from her previous mating.
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And so ensure that he will be the father of her young.
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And now, the male needs her to lay her eggs quickly
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before another male comes along and scoops out his sperm.
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He tries to lift off with the female still attached.
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But she seems reluctant to leave,
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even with the male at full throttle.
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(upbeat music)
(wings fluttering)
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He tries to persuade her with a sharp bite to the head.
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But no, she's clearly not impressed
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by him or his pickup technique.
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And there are plenty of other males around.
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All she has to do is to wait.
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Here's another male.
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(wings fluttering)
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She nips her first partner's tail
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and after all his effort, he gives up.
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And she flies off with her new partner.
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Males will jump on any female they spot.
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But females are much more choosy.
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Her former partner's sperm is scooped out
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and the new couple fly off together to lay their eggs.
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(wings fluttering)
(birds chirping)
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Undaunted, our lonely male sets out
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to look for a more willing partner.
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But he can't afford to be too preoccupied
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with the opposite sex.
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(dramatic music)
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He really needs to watch where he's going.
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It just isn't his day.
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The wasp spider has built her lethal trap in the reeds,
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in an excellent spot to ambush unwary damselflies.
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And she wraps her victim in a shroud of silk
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to stop him struggling.
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And his short life is over.
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(birds chirping)
(spider munching)
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A large lake like this is home
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to more than 20 different kinds
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of dragonflies and damselflies.
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But not all of them will spend their whole lives here.
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Both dragons and damsels are great travelers.
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Fly high and covering long distance
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in their search for water.
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Their eyes can detect polarized light reflected
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by water surface, so they can spot a pond
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from a long way off, no matter how tiny it is.
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This lily pond in a garden might be small compared
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to the lake, but it's been discovered
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by these intrepid explorers.
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A tiny realm, reigned over by an emperor dragonfly.
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(pencil scratching)
(gentle music)
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Dragonflies are more powerful and agile
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in the air than damselflies
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and they defend their own territories
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around lakes and ponds, engaging rivals in aerial dogfights.
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But this intruder is a female,
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and the male dragonfly finally realizes this.
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So he now grabs her and hooks up in midair.
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Now they must perform the same gymnastics as damselflies.
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They can even fly up together like this.
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But after mating, they separate and the female goes off
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to find somewhere to lay eggs on her own.
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(wings fluttering)
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She lays her eggs inside ponds,
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but she's very choosy about picking exactly the right place.
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The carefully tended lilies
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in this ornamental pond are just right.
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(wings fluttering)
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Sometimes, in her quest
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to give her eggs the best chance of survival,
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she decides that the perfect place is a long way
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below the surface of the water.
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But she doesn't mind getting wet.
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(birds chirping)
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A dragonfly can tell a lot about both water quality
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and the submerged vegetation from the way
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that polarized light is reflected from the surface.
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So although the whole pond looks the same to us,
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discerning emperors quickly hone in
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on the most suitable spots.
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And one egg-laying female soon attracts others.
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(upbeat music)
(wings fluttering)
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The egg-laying emperor is noticed
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by the local common blues that also use the pond.
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But why?
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Are they just curious about these lumbering monsters?
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Possibly.
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But back on the big lake,
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where there are vast swarms of common blues
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this behavior seems to be much more than just curiosity.
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(wings fluttering)
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As soon as the female emperor lands
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on floating vegetation to lay her eggs,
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she's surrounded by clouds of common blues,
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buzzing her, mobbing her, harassing her.
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Even landing on her and biting.
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Eventually it all gets too much
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for the female emperor and she gives up.
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Why do the common blues risk
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their lives chasing a dragonfly
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that is much bigger than them and could easily kill them?
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Probably because of what those emperor eggs will become.
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(water gurgling)
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(somber music)
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Eggs hatch into larvae and emperor larvae are killers.
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(dramatic music)
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Lethal predators.
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Damselflies larvae are right up there
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at the top of their menu.
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Those sharp eyes spot any movement.
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And the emperor larva stalks its lunch like a tiny cat.
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Its are eyes are huge.
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And both face forward.
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So the larvae has a stereo vision.
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It can judge its distance from a target very precisely.
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And when it's close enough,
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it deploys its secret weapon,
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jaws that can shoot out an additional half length
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of its body, a long-range strike capability that,
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for the damselfly larva comes out of nowhere.
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(dramatic music)
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The jaw snap shut and the damselfly is impaled
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on sharp spines, to be hauled in and chopped up
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by a pair of serrated blades before being swallowed.
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(dramatic music)
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It's hardly surprising that emperors
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and common blues don't get along with one another.
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(water gurgling)
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But don't feel too sorry for the damsels.
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They also are killers and use the same tricks
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as the bigger dragons, just on smaller prey.
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Water hog lice, slow moving, abundant,
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the perfect meal for a growing damselfly larva.
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(gentle music)
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And damselfly larvae are just as stealthy
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as their bigger relatives.
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Softly, softly, just waiting for the hog louse to move.
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(louse crunching)
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(gentle music)
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(dramatic music)
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The battlefield under the surface
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of a tranquil pond is no place for the fainthearted.
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And there's something else lurking down here too.
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Something hidden in the dead leaves on the lake bed.
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(dramatic music)
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The larvae of darter dragonflies.
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Squat creatures that look like bits of dead plants.
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They are ambush predators and well camouflaged.
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But these larvae have stopped hunting.
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They are about to join the emperors
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and common blues in the air above.
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(gentle music)
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And even the ugliest larva turns into a beautiful dragon.
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A common darter dragonfly,
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as elegant and colorful as any emperor.
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(gentle music)
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(birds chirping)
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Like emperors, darters defend territories around the lake.
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But they do this in a different way.
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Male emperors sometimes take a rest on a convenient perch
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but they spend most of their lives on the wing.
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They patrol their territories in the air,
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hawking up and down, occasionally hovering,
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to survey their domain and check for intruders.
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(dramatic music)
(wings fluttering)
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(birds chirping)
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Darters are less energetic.
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They find a convenient perch to keep watch,
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and every now and then fly off to check out their territory,
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often coming back to the very same spot.
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(wings fluttering)
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Sometimes they pick the flimsiest of perches.
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But they have the poise and balance of a ballerina.
264
00:22:20,660 --> 00:22:24,293
All dragonflies are true masters of the air.
265
00:22:25,160 --> 00:22:28,214
They can hover, rock steady.
266
00:22:28,214 --> 00:22:30,964
(dramatic music)
267
00:22:32,010 --> 00:22:33,603
They can fly backwards.
268
00:22:40,690 --> 00:22:43,085
And turn on a dime.
269
00:22:43,085 --> 00:22:45,668
(upbeat music)
270
00:22:52,300 --> 00:22:55,170
All these extreme aerobatics depend
271
00:22:55,170 --> 00:22:57,563
on very sophisticated wings.
272
00:23:00,880 --> 00:23:03,770
Wings that have corrugations for strength
273
00:23:05,210 --> 00:23:08,840
and complex patterns of veins that allow each wing
274
00:23:08,840 --> 00:23:12,843
to change its flapping angle independently in flight.
275
00:23:19,200 --> 00:23:24,200
But exactly how do dragonflies achieve their aerial skill?
276
00:23:25,050 --> 00:23:26,561
Ready when you are
277
00:23:26,561 --> 00:23:27,561
Yep.
278
00:23:28,660 --> 00:23:31,180
At the Royal Veterinary College in London,
279
00:23:31,180 --> 00:23:34,070
scientists are trying to find out.
280
00:23:34,070 --> 00:23:37,430
Here Richard Bomphrey uses smoke trails
281
00:23:37,430 --> 00:23:41,173
to reveal the complex patterns of airflow over the wings.
282
00:23:46,131 --> 00:23:51,131
(wings fluttering)
(gentle music)
283
00:23:56,121 --> 00:23:58,954
(lights clicking)
284
00:24:00,810 --> 00:24:04,460
And he studies the way wings move by filming them
285
00:24:04,460 --> 00:24:08,460
from every angle with multiple high-speed cameras
286
00:24:08,460 --> 00:24:11,513
which slow down the action 80 times.
287
00:24:20,550 --> 00:24:23,723
Well, that's a very nice take-off sequence of this darter.
288
00:24:26,060 --> 00:24:28,020
We can see that the wings twist
289
00:24:28,020 --> 00:24:30,293
and they bend and they change in camber,
290
00:24:31,710 --> 00:24:35,650
each of the four wings is being driven independently.
291
00:24:35,650 --> 00:24:37,280
So sometimes the fore
292
00:24:37,280 --> 00:24:40,090
and the hind wings are flapping together in phase.
293
00:24:40,090 --> 00:24:43,590
And after a little while, it switches to counter stroking,
294
00:24:43,590 --> 00:24:45,253
that's flapping out of phase.
295
00:24:47,722 --> 00:24:49,130
Now we have nine cameras here.
296
00:24:49,130 --> 00:24:52,170
And what all those views allow us to do is
297
00:24:52,170 --> 00:24:56,650
to make a three-dimensional model of the dragonfly's body
298
00:24:56,650 --> 00:25:00,010
and the wings as they undergo all these shape changes,
299
00:25:00,010 --> 00:25:01,600
the bending and the twisting
300
00:25:01,600 --> 00:25:04,170
so we can begin to understand
301
00:25:04,170 --> 00:25:06,683
how the dragonfly controls its flight.
302
00:25:08,204 --> 00:25:11,380
(gentle music)
303
00:25:11,380 --> 00:25:14,310
If we now understand how dragonflies achieve
304
00:25:14,310 --> 00:25:19,003
such mastery of the air, can we do any better?
305
00:25:19,003 --> 00:25:21,920
(wings fluttering)
306
00:25:24,040 --> 00:25:28,253
Scientist at Festo in Esslingen, Germany, have tried.
307
00:25:30,090 --> 00:25:33,710
A team of engineers here spent many years trying
308
00:25:33,710 --> 00:25:36,190
to build a robotic dragonfly
309
00:25:36,190 --> 00:25:39,080
that mimics the dragonfly's natural flight
310
00:25:39,080 --> 00:25:41,043
as Elias Knubben explains.
311
00:25:42,140 --> 00:25:43,560
We tried to come as close
312
00:25:43,560 --> 00:25:46,150
as possible to the real dragonfly.
313
00:25:46,150 --> 00:25:47,180
We did a lot of research,
314
00:25:47,180 --> 00:25:50,190
how do they adjust to different surroundings,
315
00:25:50,190 --> 00:25:51,450
how do they steer?
316
00:25:51,450 --> 00:25:54,520
And I think we came quite close to the functions.
317
00:25:54,520 --> 00:25:58,350
We are able to control the movements really precisely.
318
00:25:58,350 --> 00:26:01,870
It has to be adjusted in really very short times,
319
00:26:01,870 --> 00:26:03,415
it's only milliseconds actually,
320
00:26:03,415 --> 00:26:04,923
that you have time to react.
321
00:26:05,924 --> 00:26:10,924
(wings fluttering)
(gentle music)
322
00:26:13,010 --> 00:26:16,020
Festo's robo dragonfly can fly.
323
00:26:16,020 --> 00:26:18,090
But it takes a skillful pilot,
324
00:26:18,090 --> 00:26:22,040
controlling it remotely just to keep it in the air,
325
00:26:22,040 --> 00:26:24,280
let alone make it turn and twist
326
00:26:24,280 --> 00:26:26,746
as elegantly as the real thing.
327
00:26:26,746 --> 00:26:29,329
(gentle music)
328
00:26:32,190 --> 00:26:35,460
The pilot has to control nine different aspects
329
00:26:35,460 --> 00:26:37,520
of the wings at the same time.
330
00:26:37,520 --> 00:26:40,263
Far more complex than flying a helicopter.
331
00:26:41,170 --> 00:26:43,510
Yet real dragonflies do this
332
00:26:43,510 --> 00:26:46,093
with a brain the size of a pinhead.
333
00:26:50,300 --> 00:26:54,470
This robot dragonfly is an amazing achievement,
334
00:26:54,470 --> 00:26:56,250
but it still doesn't come close
335
00:26:56,250 --> 00:26:58,543
to matching a real dragonfly.
336
00:27:01,660 --> 00:27:04,200
To be honest real nature is even much better.
337
00:27:04,200 --> 00:27:08,760
It's not really only, pretty much smaller.
338
00:27:08,760 --> 00:27:11,400
But it's also, it has even much more functions
339
00:27:11,400 --> 00:27:13,540
and there's so much more to learn.
340
00:27:13,540 --> 00:27:15,743
We're looking forward to do this.
341
00:27:15,743 --> 00:27:18,710
(wings whirring)
342
00:27:18,710 --> 00:27:21,720
But to be fair to Festo's engineers,
343
00:27:21,720 --> 00:27:25,300
real dragonflies have been practicing the art of flight
344
00:27:25,300 --> 00:27:29,500
for 330 millions longer than they have.
345
00:27:29,500 --> 00:27:32,260
And in that time, nature has come up
346
00:27:32,260 --> 00:27:35,223
with more uses for wings than just flying.
347
00:27:36,292 --> 00:27:37,380
(gentle music)
348
00:27:37,380 --> 00:27:40,193
These particularly beautiful wings,
349
00:27:41,050 --> 00:27:45,730
with deep blue patches, belong to a banded damoiselle.
350
00:27:47,156 --> 00:27:50,156
(pencil scratching)
351
00:27:56,830 --> 00:28:00,150
Banded damoiselles avoid the busy lake.
352
00:28:00,150 --> 00:28:04,992
They prefer flowing water and live on a nearby river.
353
00:28:04,992 --> 00:28:07,742
(birds chirping)
354
00:28:09,540 --> 00:28:11,940
Unlike most damselflies,
355
00:28:11,940 --> 00:28:16,940
banded damoiselle males occupy small territories strung out
356
00:28:17,180 --> 00:28:19,280
along the banks of the river.
357
00:28:19,280 --> 00:28:21,013
And they defend them in style,
358
00:28:22,221 --> 00:28:23,054
(gentle music)
359
00:28:23,054 --> 00:28:26,840
by flicking their wings, showing off their colors
360
00:28:28,640 --> 00:28:30,830
and so signaling ownership
361
00:28:30,830 --> 00:28:33,533
of their exclusive riverside property.
362
00:28:52,560 --> 00:28:56,353
Not all banded damoiselles are created equal.
363
00:28:59,320 --> 00:29:01,693
The wing spots vary in size.
364
00:29:06,790 --> 00:29:10,070
This can be hard for us humans to spot,
365
00:29:10,070 --> 00:29:13,713
even comparing museum specimens side by side.
366
00:29:15,810 --> 00:29:18,680
But the difference are quickly picked out
367
00:29:18,680 --> 00:29:21,823
by those sharp damselfly eyes.
368
00:29:24,147 --> 00:29:29,147
(wings fluttering)
(gentle music)
369
00:29:39,210 --> 00:29:42,600
The fittest males have the biggest spots.
370
00:29:42,600 --> 00:29:46,433
An arrival with smaller spots soon realizes his place
371
00:29:47,514 --> 00:29:49,514
and gives in gracefully.
372
00:29:58,400 --> 00:30:01,800
But if a male with similar size spots tries
373
00:30:01,800 --> 00:30:06,423
to take over the territory, a different strategy is needed.
374
00:30:07,390 --> 00:30:10,330
A fight with an equal could be dangerous.
375
00:30:10,330 --> 00:30:12,743
It's better to just behave like gentlemen.
376
00:30:14,150 --> 00:30:16,710
So each male shows off his spots
377
00:30:16,710 --> 00:30:19,400
with exaggerated wing beats,
378
00:30:19,400 --> 00:30:23,053
until one of them finally accepts defeat and retreats.
379
00:30:24,115 --> 00:30:29,115
(wings fluttering)
(gentle music)
380
00:30:37,014 --> 00:30:40,877
Often, other males from neighboring territories join in,
381
00:30:40,877 --> 00:30:42,410
and they all sort out
382
00:30:42,410 --> 00:30:45,773
the neighborhood hierarchy between themselves.
383
00:30:48,060 --> 00:30:52,490
For an insect, this is really sophisticated behavior.
384
00:30:52,490 --> 00:30:56,490
Each male is able to decide the best strategy to follow,
385
00:30:56,490 --> 00:30:59,813
based on his estimation of the toughness of a rival.
386
00:31:00,759 --> 00:31:04,266
(train whistling)
387
00:31:04,266 --> 00:31:09,266
(birds chirping)
(wheels clacking)
388
00:31:10,753 --> 00:31:11,870
(gentle music)
389
00:31:11,870 --> 00:31:14,223
Summer is now reaching its height.
390
00:31:15,466 --> 00:31:16,520
(birds chirping)
391
00:31:16,520 --> 00:31:18,080
And back on the big lake,
392
00:31:18,080 --> 00:31:23,080
more and more dragons and damsels crowd into the reeds.
393
00:31:23,422 --> 00:31:26,760
(wings fluttering)
394
00:31:26,760 --> 00:31:29,660
These are four spotted chaser dragonflies
395
00:31:32,262 --> 00:31:35,240
and they gather in huge roosts every evening
396
00:31:35,240 --> 00:31:37,850
to wake at dawn ready to find somewhere
397
00:31:37,850 --> 00:31:39,413
to claim as their territory.
398
00:31:40,920 --> 00:31:43,507
Not easy when there are so many rivals.
399
00:31:45,130 --> 00:31:47,847
(wings fluttering)
400
00:31:47,847 --> 00:31:50,597
(birds chirping)
401
00:31:57,820 --> 00:32:00,913
Space in the reeds is now at a premium.
402
00:32:03,830 --> 00:32:06,510
But that's not a problem for another species
403
00:32:06,510 --> 00:32:09,443
of damselfly that has now joined the throng.
404
00:32:10,730 --> 00:32:12,343
The common red-eye.
405
00:32:13,547 --> 00:32:16,130
(upbeat music)
406
00:32:17,810 --> 00:32:19,950
Red-eyes perch on anything floating
407
00:32:19,950 --> 00:32:22,443
on the surface, not matter how small.
408
00:32:26,820 --> 00:32:29,790
Each a captain of its own little ship
409
00:32:29,790 --> 00:32:32,763
as it drifts over the surface of the lake.
410
00:32:37,578 --> 00:32:40,328
(birds chirping)
411
00:32:46,886 --> 00:32:49,773
(wings fluttering)
412
00:32:49,773 --> 00:32:53,490
But they also sometimes get unwitting help
413
00:32:53,490 --> 00:32:55,833
from bigger residents of the lake.
414
00:33:05,310 --> 00:33:09,423
The feather from a swan makes an excellent raft.
415
00:33:12,961 --> 00:33:15,711
(birds chirping)
416
00:33:18,670 --> 00:33:21,570
And the red-eyes defend their little boats
417
00:33:21,570 --> 00:33:24,453
against the ever inquisitive common blues.
418
00:33:29,850 --> 00:33:32,460
A flick of the wings, a warning,
419
00:33:32,460 --> 00:33:34,663
there's no more room on board.
420
00:33:35,652 --> 00:33:40,652
(wings fluttering)
(birds chirping)
421
00:33:43,312 --> 00:33:45,700
And there's not much more space in the reeds,
422
00:33:45,700 --> 00:33:50,700
now crowded with males, just hanging out,
423
00:33:51,390 --> 00:33:53,423
waiting for a female to turn up.
424
00:33:56,950 --> 00:34:00,302
(gentle music)
425
00:34:00,302 --> 00:34:03,969
And when one does, she turns a lot of heads.
426
00:34:06,704 --> 00:34:09,230
(wings fluttering)
427
00:34:09,230 --> 00:34:11,260
With the season in full swing,
428
00:34:11,260 --> 00:34:13,973
there's a lot of desperate males around.
429
00:34:18,550 --> 00:34:23,263
A female common blue and she seems available.
430
00:34:31,495 --> 00:34:35,910
But this is an azure damselfly, trying it on.
431
00:34:35,910 --> 00:34:38,000
He might look like a common blue,
432
00:34:38,000 --> 00:34:40,260
but he's a totally different species
433
00:34:40,260 --> 00:34:41,983
and he simply can't hook up.
434
00:34:54,850 --> 00:34:57,403
Now a red-eye tries his luck.
435
00:35:04,010 --> 00:35:07,013
This is definitely not going to work.
436
00:35:16,733 --> 00:35:21,723
Finally a genuine common blue and her patience is rewarded.
437
00:35:26,155 --> 00:35:29,072
(wings fluttering)
438
00:35:35,240 --> 00:35:40,110
In these crowded skies, a male has only one mission.
439
00:35:40,110 --> 00:35:44,323
To attach himself to a female and stay attached.
440
00:35:45,250 --> 00:35:46,100
It's the best way
441
00:35:46,100 --> 00:35:49,253
to avoid another male mating with his partner.
442
00:35:50,970 --> 00:35:53,563
But it looks like hard work for the female.
443
00:35:55,670 --> 00:35:59,223
Though her male does have his uses.
444
00:35:59,223 --> 00:36:02,140
(wings fluttering)
445
00:36:03,720 --> 00:36:06,420
To find the best spot to lay her eggs,
446
00:36:06,420 --> 00:36:11,083
a female damsel must sometimes submerge herself completely.
447
00:36:11,931 --> 00:36:13,790
(dramatic music)
448
00:36:13,790 --> 00:36:15,960
Being smaller than dragonflies,
449
00:36:15,960 --> 00:36:19,433
she can get trapped by the surface tension of the water.
450
00:36:20,410 --> 00:36:24,310
The male, however, stays dry above the surface.
451
00:36:24,310 --> 00:36:26,040
And that can be important.
452
00:36:26,040 --> 00:36:29,130
He may be needed to haul her out of the water
453
00:36:29,130 --> 00:36:30,833
if she gets into difficulties.
454
00:36:31,728 --> 00:36:36,728
(wings fluttering)
(dramatic music)
455
00:36:40,699 --> 00:36:42,770
But if the female gets too wet,
456
00:36:42,770 --> 00:36:45,773
even the male's assistance may not be enough.
457
00:36:52,510 --> 00:36:54,703
Males don't like getting wet.
458
00:36:58,161 --> 00:37:01,200
And if a female submerges particularly deeply,
459
00:37:01,200 --> 00:37:04,543
her mate just abandons her to her fate.
460
00:37:08,344 --> 00:37:11,730
(water gurgling)
461
00:37:11,730 --> 00:37:14,063
Now, she's on her own.
462
00:37:24,880 --> 00:37:26,810
Without a male to help,
463
00:37:26,810 --> 00:37:30,703
it's a real struggle to clamber back out of the water.
464
00:37:46,343 --> 00:37:49,810
As long as a male stays attached to his partner,
465
00:37:49,810 --> 00:37:51,760
no other male can steal her
466
00:37:51,760 --> 00:37:56,193
and he can be sure that he will be the father of those eggs.
467
00:37:59,300 --> 00:38:02,460
But all these single males don't just give up.
468
00:38:02,460 --> 00:38:06,160
They constantly hassle egg-laying pairs.
469
00:38:06,160 --> 00:38:09,010
And if a pair crashes onto the surface,
470
00:38:09,010 --> 00:38:12,650
the male might drop his mate before he gets soaked,
471
00:38:12,650 --> 00:38:16,640
and then one of the single males can grab the female.
472
00:38:16,640 --> 00:38:19,557
(wings fluttering)
473
00:38:22,220 --> 00:38:27,050
But this time, they've picked an unusually feisty male.
474
00:38:27,050 --> 00:38:29,670
He hangs on, even though he's now stuck
475
00:38:29,670 --> 00:38:31,693
on the surface film himself.
476
00:38:34,260 --> 00:38:36,700
They're so busy fighting over the female
477
00:38:36,700 --> 00:38:38,420
they're getting careless
478
00:38:38,420 --> 00:38:41,420
and all this activity attracts the attention
479
00:38:41,420 --> 00:38:43,871
of monsters from the deep.
480
00:38:43,871 --> 00:38:46,621
(dramatic music)
481
00:38:54,940 --> 00:38:57,773
(water splashing)
482
00:39:10,606 --> 00:39:15,189
Trout snatch up anything edible trapped on the surface.
483
00:39:21,810 --> 00:39:26,210
This male has somehow avoided becoming fish food.
484
00:39:26,210 --> 00:39:29,887
But that was his good luck used up for the day.
485
00:39:29,887 --> 00:39:31,560
(dramatic music)
486
00:39:31,560 --> 00:39:33,700
His struggles create ripples
487
00:39:33,700 --> 00:39:36,453
and for the creatures that live on the surface film,
488
00:39:37,510 --> 00:39:40,644
that is like sounding a dinner bell.
489
00:39:40,644 --> 00:39:43,394
(dramatic music)
490
00:39:45,260 --> 00:39:48,700
Pond skaters can detect these vibrations
491
00:39:48,700 --> 00:39:51,819
and pinpoint their source precisely.
492
00:39:51,819 --> 00:39:54,440
(dramatic music)
493
00:39:54,440 --> 00:39:57,863
Swarms of then hone in on the helpless damsel.
494
00:39:59,633 --> 00:40:02,550
(wings fluttering)
495
00:40:08,770 --> 00:40:11,140
They pierce the damselfly's skin
496
00:40:11,140 --> 00:40:16,130
with their sharp mouthparts, inject a digestive toxin
497
00:40:16,130 --> 00:40:20,271
and then suck up nutritious dragonfly soup.
498
00:40:20,271 --> 00:40:25,271
(pond skater slurping)
(dramatic music)
499
00:40:51,426 --> 00:40:52,260
(wing fluttering)
500
00:40:52,260 --> 00:40:56,863
Great flotillas of pond skaters patrol the lake's surface.
501
00:40:57,864 --> 00:41:00,310
(flies buzzing)
502
00:41:00,310 --> 00:41:02,280
And they're never short of food.
503
00:41:02,280 --> 00:41:04,540
For the female damsels have
504
00:41:04,540 --> 00:41:07,343
to settle there if they're to lay their eggs.
505
00:41:11,760 --> 00:41:15,100
But both dragons and damsels spend
506
00:41:15,100 --> 00:41:18,956
as little time as possible near the surface.
507
00:41:18,956 --> 00:41:20,600
(wings fluttering)
508
00:41:20,600 --> 00:41:24,070
Darters, however, manage to lay their eggs in flight,
509
00:41:24,070 --> 00:41:26,213
just touching the water briefly.
510
00:41:28,830 --> 00:41:33,020
Darters do this as a pair, a display of precision flying
511
00:41:33,020 --> 00:41:36,048
that human engineers can only dream of.
512
00:41:36,048 --> 00:41:38,110
(gentle music)
513
00:41:38,110 --> 00:41:41,783
With each dip, the female releases a few eggs.
514
00:41:49,320 --> 00:41:52,103
Eight wings and two brains working together.
515
00:41:53,900 --> 00:41:57,613
The slightest miscalculation would end in disaster.
516
00:42:10,290 --> 00:42:13,270
Damselflies have a different strategy
517
00:42:13,270 --> 00:42:15,573
to avoid the dangers of the lake.
518
00:42:17,990 --> 00:42:21,840
Egg-laying pairs, like these azure damselflies,
519
00:42:21,840 --> 00:42:23,913
often gather in large numbers.
520
00:42:26,280 --> 00:42:29,460
So there's less chance of being the unlucky couple
521
00:42:29,460 --> 00:42:31,023
if a predator does show up.
522
00:42:32,006 --> 00:42:34,807
(flies buzzing)
523
00:42:34,807 --> 00:42:37,724
(wings fluttering)
524
00:42:41,930 --> 00:42:45,380
This male has sensed something is wrong
525
00:42:46,260 --> 00:42:49,593
and is desperately trying to pull his mate from the water.
526
00:42:52,610 --> 00:42:56,655
But however much he flaps, he can't take off.
527
00:42:56,655 --> 00:42:59,405
(dramatic music)
528
00:43:03,758 --> 00:43:05,091
And this is why.
529
00:43:07,710 --> 00:43:09,460
An underwater predator,
530
00:43:09,460 --> 00:43:12,790
attracted by the crowds of busy damselflies,
531
00:43:12,790 --> 00:43:16,153
has bitten off her abdomen and made a meal of it.
532
00:43:20,750 --> 00:43:23,180
Her mate is still trying to rescue her
533
00:43:23,180 --> 00:43:25,200
and fly her to safety.
534
00:43:25,200 --> 00:43:26,263
But it's too late.
535
00:43:32,012 --> 00:43:37,012
(gentle music)
(wings fluttering)
536
00:43:42,180 --> 00:43:46,250
The others carry on egg laying as if nothing has happened,
537
00:43:46,250 --> 00:43:49,746
paying no attention to the unlucky female
538
00:43:49,746 --> 00:43:54,683
who just manages to haul herself onto a lily leaf.
539
00:43:58,210 --> 00:44:00,943
Always on the lookout for a single lady,
540
00:44:02,490 --> 00:44:05,743
a common blue thinks he's found an opportunity.
541
00:44:07,410 --> 00:44:09,923
But soon realizes his mistake.
542
00:44:11,800 --> 00:44:15,939
She is mortally injured and beyond rescue.
543
00:44:15,939 --> 00:44:18,522
(somber music)
544
00:44:26,639 --> 00:44:29,556
(thunder rumbling)
545
00:44:34,809 --> 00:44:38,060
(gentle music)
546
00:44:38,060 --> 00:44:39,910
For these tiny creatures,
547
00:44:39,910 --> 00:44:42,963
raindrops are as dangerous as cannonballs.
548
00:44:45,651 --> 00:44:48,318
(rain dripping)
549
00:44:55,360 --> 00:44:57,333
Time to find shelter.
550
00:45:01,748 --> 00:45:04,665
(thunder rumbling)
551
00:45:18,010 --> 00:45:22,853
But the season is nearly over and time is precious.
552
00:45:25,620 --> 00:45:28,140
As soon as the sun returns,
553
00:45:28,140 --> 00:45:31,273
male damoiselles are back on their territories.
554
00:45:38,345 --> 00:45:42,090
It's now almost autumn, and while other damsels
555
00:45:42,090 --> 00:45:44,540
and dragons are winding down,
556
00:45:44,540 --> 00:45:48,433
one kind of damselfly is just getting started.
557
00:45:50,720 --> 00:45:54,550
An unusual species that's attracted a lot of attention
558
00:45:54,550 --> 00:45:57,913
in recent years, the willow emerald.
559
00:46:00,060 --> 00:46:01,790
In the last few decades,
560
00:46:01,790 --> 00:46:05,430
this species has moved steadily north through Europe
561
00:46:05,430 --> 00:46:06,730
and has even made the hop
562
00:46:06,730 --> 00:46:09,603
across the North Sea and invaded England.
563
00:46:14,250 --> 00:46:17,910
The British Dragonfly Society have been keeping a keen eye
564
00:46:17,910 --> 00:46:22,910
on the spread of these invaders, as Fiona McKenna explains.
565
00:46:25,490 --> 00:46:29,660
The willow emerald damselfly arrived in roughly 2007 is
566
00:46:29,660 --> 00:46:32,593
when we got the first record of a female in the UK.
567
00:46:33,960 --> 00:46:35,180
Their rapid invasion
568
00:46:35,180 --> 00:46:39,420
of Northern Europe is a consequence of climate change
569
00:46:39,420 --> 00:46:40,800
which is why it's important
570
00:46:40,800 --> 00:46:45,110
for scientists and naturalists to chart its spread.
571
00:46:45,110 --> 00:46:47,060
It's a marker that can tell us
572
00:46:47,060 --> 00:46:50,573
how a warmer climate might effect the natural world.
573
00:46:53,580 --> 00:46:56,380
And the spread of the willow emerald is easy
574
00:46:56,380 --> 00:46:59,483
to track because of their strange lifestyle.
575
00:47:00,500 --> 00:47:03,640
It's quite unusual, it's different to other damselflies.
576
00:47:03,640 --> 00:47:05,723
You have to look up in trees for it.
577
00:47:07,060 --> 00:47:08,880
Traditionally it's associated with willow,
578
00:47:08,880 --> 00:47:10,743
hence it being called willow emerald.
579
00:47:12,460 --> 00:47:14,500
But it has been known to utilize
580
00:47:14,500 --> 00:47:16,123
other types of trees as well.
581
00:47:19,210 --> 00:47:21,220
And it also lays its eggs into bark,
582
00:47:21,220 --> 00:47:23,470
so it's got very unusual egg-laying behavior.
583
00:47:24,900 --> 00:47:27,483
(gentle music)
584
00:47:29,180 --> 00:47:32,400
The female has sharp blades at the tip
585
00:47:32,400 --> 00:47:34,610
of her abdomen which she uses
586
00:47:34,610 --> 00:47:36,833
to cut holes in the bark of trees.
587
00:47:56,310 --> 00:47:59,880
They leave very distinctive little oval scars
588
00:47:59,880 --> 00:48:01,630
where they've laid their eggs into.
589
00:48:02,550 --> 00:48:05,743
The scarred branches are easy to see.
590
00:48:09,470 --> 00:48:10,730
So you don't even need
591
00:48:10,730 --> 00:48:13,640
to identify the damselflies themselves
592
00:48:13,640 --> 00:48:16,233
to follow the species spread northwards.
593
00:48:17,800 --> 00:48:20,230
Of all the dragons and damsels,
594
00:48:20,230 --> 00:48:23,783
willow emeralds are among the last to take to the wing.
595
00:48:25,667 --> 00:48:29,358
And they must work quickly before the frost arrives.
596
00:48:29,358 --> 00:48:31,941
(gentle music)
597
00:48:34,000 --> 00:48:36,230
Autumn brings the stories
598
00:48:36,230 --> 00:48:40,243
of all dragonflies and damselflies to a close.
599
00:49:07,240 --> 00:49:10,053
Lakes and rivers seem deserted.
600
00:49:12,840 --> 00:49:14,363
But not so.
601
00:49:16,350 --> 00:49:19,410
Below the surface, the next generation,
602
00:49:19,410 --> 00:49:24,280
the legacy of those frantic matings of summer are waiting,
603
00:49:24,280 --> 00:49:27,840
ready to take to the air when the weather warms again
604
00:49:28,860 --> 00:49:33,860
as they have done for the last 330 million years.
605
00:49:35,441 --> 00:49:38,024
(upbeat music)
46241
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