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The ability to move through
the air in any direction you wish,
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to cross continents and oceans,
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00:00:26,507 --> 00:00:30,160
to range over forests
and deserts and mountains,
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00:00:30,480 --> 00:00:35,951
all this birds have been able
to do for 150 million years.
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00:00:36,272 --> 00:00:41,340
But they weren't the first
or indeed the last, in the skies.
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We are setting out to explore
one of the most astonishing stories
in the natural world.
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The way in which animals manage
to rise up from the surface of the Earth,
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and colonise the air.
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From the dazzling aerobatics
of the insects...
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00:01:06,623 --> 00:01:10,567
to the majesty
of ancient winged reptiles.
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00:01:17,522 --> 00:01:20,419
The splendour and agility of birds...
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and the sonar guided precision
of night flying bats.
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Flight has been the key to the success
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of some of our planet's most
remarkable inhabitants.
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To analyse their spectacular skills,
we will use the latest technology.
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And we will travel around the world.
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From the jungles of Borneo,
to the fossil-filled rocks of China,
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and the Cloud Forests of Ecuador.
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We will take you into the air...
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and travel with animals as they fly.
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Evidence for the very beginnings
of this astonishing story
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can be found close to home
in The Fens of Cambridgeshire.
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Here live creatures that have an ancestry
stretching back millions of years.
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Nobody knows exactly
how the first flying animals
in the world evolved,
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but there are creatures alive today,
that can take us back
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to those far-distant, remarkable times,
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and they live - surprisingly - under water.
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Looking down through
the surface to the riverbed,
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is like traveling back
in time, over 320 million years.
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It was then, in an age long before
even the dinosaurs evolved,
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that creatures like this,
first appeared in the waters
of the Earth.
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It's an insect.
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A ferocious predator
with jaws like a mechanical grab.
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00:04:16,847 --> 00:04:20,070
It seems unlikely
that this animal's ancestors
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were among the first
creatures ever to fly.
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But this one is not yet adult,
it's a larva,
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and it doesn't spend all
its life in the water.
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It has another life,
and another body above the surface.
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Early one morning, it climbs up a reed.
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A split appears in its skin,
and a very different-looking
creature begins to emerge.
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00:05:01,631 --> 00:05:05,757
It has four lumps on its back,
that might perhaps ancestrally
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have become either gills,
or protective armour plates.
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But now they develop
into something very different.
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Wings.
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It has two pairs of them.
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Liquid from its body is pumped-down
along veins, to stretch them tight.
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00:05:37,222 --> 00:05:40,869
As they dry in the sun, they harden.
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00:05:49,985 --> 00:05:54,366
The water-living dragon
has become the dragonfly.
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00:05:54,848 --> 00:05:58,980
And the four-winged apparatus
that he uses to get into the air,
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is the earliest that we know.
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00:06:07,211 --> 00:06:10,947
Imprints of such wings have been found
in rocks that were laid down
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on the bottom
of ancient lakes and streams.
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00:06:17,099 --> 00:06:21,765
This specimen is
about 150 million years old.
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00:06:23,360 --> 00:06:28,945
And this wing is double that age
at nearly 300 million years old.
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00:06:33,639 --> 00:06:38,560
Ancient and modern wings share
a structure that is strikingly similar.
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00:06:41,303 --> 00:06:46,726
So today's dragonflies are amazingly,
living fossils that can show us
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how the very first flyers
overcame the pull of gravity,
and took to the skies.
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Their wings are marvels
of natural engineering.
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But to see how they lift
the dragonfly into the air,
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we need to slow the action down.
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00:07:33,424 --> 00:07:37,539
In principle, it looks fairly simple,
each wing beats down,
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pushing on the air below,
so lifting the dragonfly up.
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00:07:42,904 --> 00:07:46,215
But each beat also creates
another air current
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that lifts the dragonfly
in a very different way.
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And I can demonstrate it,
using this strip of paper
to represent a wing.
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If I blow across the top of it,
it'll rise. Watch.
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That is because the faster air moves,
the lower its pressure.
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So I created a lower pressure
above the wing,
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and in consequence
it was sucked upwards.
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The problem for a flying animal,
is to recreate
that difference in air-speed.
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The way the dragonfly
does this is remarkable.
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As it moves through the air,
we can see that it twists
its wings at different angles.
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On the powerful down-beat,
it holds them at a slight
upwards angle to the air flow,
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00:09:01,471 --> 00:09:05,500
and this produces an extraordinary
effect above the wing.
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00:09:06,382 --> 00:09:11,894
It creates a swirl
behind the leading edge,
which spins the air round,
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00:09:11,965 --> 00:09:16,399
increasing the speed
of the air current
over the top of the wing,
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00:09:16,497 --> 00:09:22,963
and just a tiny increasing speed
generates a significant upwards force,
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lifting up the wing, and the dragonfly.
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00:09:30,689 --> 00:09:34,661
The dragonfly can then change
the direction of its wing beats,
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00:09:34,953 --> 00:09:38,082
to propel it forwards, as well as upwards.
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00:09:44,267 --> 00:09:49,643
Remarkably, a dragonfly can beat
each of its four wings independently.
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00:09:52,736 --> 00:09:57,763
And that enables it to perform
an astonishing variety of manoeuvres.
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It can hover.
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00:10:05,623 --> 00:10:08,123
It can glide.
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00:10:09,320 --> 00:10:11,855
It can even fly backwards.
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For maximum power,
it beats both pairs together,
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00:10:21,188 --> 00:10:23,932
and can make really sharp turns.
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00:10:26,521 --> 00:10:29,725
So the very first dragonflies were able
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to extend their territories far and wide.
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00:10:36,249 --> 00:10:39,653
And as more insects
joined them in the skies,
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the dragonflies had the skills
to be deadly aerial hunters.
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00:11:00,419 --> 00:11:04,521
The ability to fly brought
great advantages to those early insects.
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It enabled them to find food,
to escape from predators,
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00:11:09,538 --> 00:11:14,989
and particularly important,
to travel to new territories
in search of a mate.
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00:11:19,498 --> 00:11:23,191
Damselflies like their
close relations dragonflies,
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have remained virtually unchanged
for millions of years.
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00:11:28,531 --> 00:11:32,662
Mating can be quite complicated
when both partners can fly,
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and these were among
the first kind of animals
that had to deal with that problem.
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00:11:40,330 --> 00:11:43,693
The blue colour of this one,
shows that it's a male.
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To attract a female, a male must have
something to offer her. A territory.
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He chooses a stretch of water,
that is likely to contain
plenty of food for his offspring.
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Then he guards this territory
against any rivals.
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Until a female flies in and joins him.
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He must now grab her before she changes
her mind, in mid-air if necessary.
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00:12:22,095 --> 00:12:27,381
He uses claspers at the tip
of his abdomen,
to grip her behind her neck.
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00:12:28,232 --> 00:12:33,518
Amazingly, the pair are able to
coordinate the beats of their eight wings.
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00:12:35,332 --> 00:12:41,363
They may mate in the air,
or choose a secluded perch
where they'll be safe from predators.
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They then fly around the territory,
laying their fertilized eggs.
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Flight enabled insects
to invade part of the planet
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that until then, had been uninhabited:
The air.
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00:13:08,951 --> 00:13:11,451
And they flourished.
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00:13:13,387 --> 00:13:19,964
So, 320 million years ago,
the skies thronged with flying insects.
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00:13:20,603 --> 00:13:24,775
But those early four-wing forms
were destined to produce
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a whole range of spectacular,
highly specialized flyers.
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The need to lay eggs in water,
tied the first dragonflies
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to streams and ponds like these.
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00:13:39,673 --> 00:13:43,966
But then, around 20 million years
after their arrival,
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00:13:44,106 --> 00:13:48,936
a new kind of flying insect appeared
with no such ties to water.
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00:13:51,375 --> 00:13:55,862
Proof of their success
can be found almost wherever you look,
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and few places more abundantly
than in Borneo.
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00:14:17,433 --> 00:14:20,526
The very first flyers
had two pairs of wings,
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00:14:20,912 --> 00:14:23,742
now we're looking for their successors.
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00:14:25,721 --> 00:14:28,888
One group of creatures
adapted that original
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four-wing design with such success,
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00:14:32,954 --> 00:14:36,119
that they diversified
into the most numerous
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00:14:36,197 --> 00:14:39,583
and widespread group of animals
on the entire planet,
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and you can find some
of the most spectacular examples,
down there in the rainforest.
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Not all insects are hunters,
some are strict vegetarians like this one.
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This it is the land living equivalent
to that underwater monster,
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the dragonfly larva.
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But this larva instead
of catching little fish
and water fleas, munches wood pulp.
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00:15:28,654 --> 00:15:32,491
The trouble is, that wood pulp
is not very nutritious,
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00:15:32,905 --> 00:15:36,834
and this creature has to eat it
for at least a year,
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before it's this size,
which is full grown.
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00:15:40,599 --> 00:15:46,581
But then this larva will turn
into an adult, which is equally monstrous.
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Emerging from beneath the ground,
where it is lived and fed
as a larva, is a beetle.
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One of the biggest in the world.
The Atlas beetle.
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00:16:10,487 --> 00:16:13,844
Males like this one
are armed with long horns,
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powerful weapons with which to
compete with rivals for a mate.
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00:16:20,035 --> 00:16:23,625
It now spends most of its time
above the ground,
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00:16:23,777 --> 00:16:29,775
barging its way through
the undergrowth, where it feeds
on tree-sap and fallen fruit.
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00:16:34,262 --> 00:16:39,110
This hefty, powerful creature
may not look as if it could fly.
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But it can.
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At key moments in its life
it takes to the air
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to look for new sources of food,
and of course, a female.
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All this burrowing and munching around,
could injure delicate flight wings.
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00:17:08,387 --> 00:17:12,032
So beetles have hardened the front pair
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to form this pair of protective covers,
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00:17:16,523 --> 00:17:21,566
and the delicate flight pair,
are stowed away in safety, underneath.
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00:17:30,800 --> 00:17:36,455
To see how the wings are
folded away beneath their covers,
we need to wait for take-off.
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As it flaps, sprung hinges
click-open and the wings
are stretched to their full size.
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The working wings create lift in just
the same way that the dragonfly wings do,
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00:18:22,369 --> 00:18:27,117
and the front wings, which have now
become covers, are held out to the side.
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00:18:27,854 --> 00:18:31,064
And their shape does
give a little extra lift.
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00:18:31,795 --> 00:18:35,499
But it's clear that this is really,
rather a clumsy flyer.
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Landings can be clumsy too.
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And now those fragile wings
must be carefully packed away,
beneath their covers.
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00:18:54,420 --> 00:18:59,054
They're guided by a line of tiny hairs
at the base of the abdomen.
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00:19:02,766 --> 00:19:06,749
These grip the wings and
help push them into position.
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The beetle does it
with all the care and precision
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that a skydiver uses
when packing away his parachute.
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00:19:21,141 --> 00:19:25,617
Once in a new territory, it will
stake out a fresh source of food,
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and then defend it
until a female arrives.
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The beetle way of life proved
astonishingly successful.
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There are over 370,000 different
species of beetle, so far discovered.
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Unbelievable figure.
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So early on, the beetles managed
to fly as much as they need to,
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with just one pair of wings.
169
00:19:58,608 --> 00:20:02,182
And then, around 57 million years ago,
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came another key development
in the history of flight.
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A new type of insect appeared,
with two pairs of wings
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that became in effect, huge billboards.
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Wings that are perhaps
the most dazzlingly beautiful of all.
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Butterflies.
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00:20:34,538 --> 00:20:40,239
To create these extraordinary wings,
the butterflies evolved
a complex life cycle.
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00:20:41,199 --> 00:20:46,272
They hatch from eggs, as little worms
with legs - caterpillars.
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00:20:48,359 --> 00:20:53,662
But, unlike many beetle grubs,
caterpillars find their food
above ground,
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where they're very vulnerable
to predators.
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00:20:56,191 --> 00:20:58,788
So they have evolved several strategies
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00:20:59,087 --> 00:21:04,073
to accumulate all the body mass
they will need, to become flying adults.
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00:21:05,693 --> 00:21:09,744
The first is to eat as much as they can,
as quickly as they can.
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00:21:10,550 --> 00:21:14,486
Many are able to reach full size,
in just a matter of weeks.
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00:21:18,125 --> 00:21:23,473
Of course, a little thin-skinned,
fat-filled sausage
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00:21:23,877 --> 00:21:27,530
is a tempting morsel
for any bird or reptile.
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00:21:27,714 --> 00:21:31,048
So caterpillars have to have
ways of defending themselves.
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00:21:31,763 --> 00:21:36,025
This one, which is the caterpillar
of a lovely swallowtail butterfly
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has disguised itself, as a bird dropping.
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00:21:40,966 --> 00:21:44,646
And if that doesn't deceive a bird,
and a bird goes for it,
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00:21:44,985 --> 00:21:47,485
it has another form of defence.
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00:21:55,025 --> 00:21:58,438
It's emitted a rather
unpleasant smell as well.
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00:22:07,273 --> 00:22:11,213
In the struggle to survive long enough
to become winged adults,
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00:22:11,367 --> 00:22:16,557
other caterpillars have developed
other equally ingenious forms of defence.
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00:22:18,339 --> 00:22:24,072
Concealed within these fluffy strands
are short stinging spikes.
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00:22:27,053 --> 00:22:32,309
And this one is armed with long spines
which have really painful stings.
195
00:22:32,717 --> 00:22:36,015
Not only that, it has
these bright warning colours
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00:22:36,301 --> 00:22:40,938
to tell any potential predator
that they'll be in trouble if they attack.
197
00:22:44,581 --> 00:22:50,195
This caterpillar may appear
to be dangerous,
but it is in fact a fraud.
198
00:22:50,728 --> 00:22:53,228
The spines don't sting at all.
199
00:22:53,430 --> 00:22:57,952
It's relying on its disguise to make
a potential predator think twice,
200
00:22:58,494 --> 00:23:00,994
and leave it alone.
201
00:23:06,505 --> 00:23:09,620
Or... you can simply hide.
202
00:23:10,914 --> 00:23:17,267
These little tents, have been made
by the caterpillars
of a Skipper butterfly.
203
00:23:18,064 --> 00:23:23,619
Each caterpillar's started by making
a circular cut in the edge of the leaf,
204
00:23:23,809 --> 00:23:28,536
but it's left one segment uncut,
so it can act as a hinge.
205
00:23:28,918 --> 00:23:32,122
Then it pulls over the whole segment
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00:23:32,486 --> 00:23:37,757
and hides beneath to munch away
at the tissues of the leaf.
207
00:23:38,459 --> 00:23:44,083
And if I just pull it up..
There's a caterpillar.
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00:23:48,734 --> 00:23:51,775
Caterpillars that survive
this hazardous stage,
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can now build their wings
and turn into adults.
210
00:23:56,208 --> 00:23:59,556
They undergo
a truly radical transformation.
211
00:24:00,280 --> 00:24:04,259
Instead of shedding a final layer
of skin as the dragonfly does,
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00:24:04,658 --> 00:24:08,703
a caterpillar first surrounds itself,
with a protective shell
213
00:24:08,790 --> 00:24:11,258
to act as a sort of changing room.
214
00:24:11,458 --> 00:24:15,497
Within which it dismantles and then
completely reconstructs its body.
215
00:24:17,244 --> 00:24:21,788
After around 10 days,
it emerges as a butterfly.
216
00:24:23,689 --> 00:24:29,908
Now fluid pumps along veins and the wings,
to stretch them out to their full size.
217
00:24:32,810 --> 00:24:35,390
And then, it is ready to fly.
218
00:24:45,437 --> 00:24:49,985
Butterflies live on nectar
which they collect from flowers.
219
00:24:51,246 --> 00:24:56,345
Like dragonflies and beetles,
they also fly to find a mate.
220
00:24:56,642 --> 00:25:01,472
But the way they beat their colourful wings
is significantly different.
221
00:25:15,766 --> 00:25:19,917
This lovely creature
has two pairs of wings,
222
00:25:20,219 --> 00:25:23,898
but it has in effect,
turned them into one.
223
00:25:24,915 --> 00:25:31,734
It's done that quite simply,
by overlapping the larger front pair,
over the smaller hind pair,
224
00:25:31,819 --> 00:25:37,505
so that when the front pair beat-down,
they automatically
press down the lower pair.
225
00:25:38,278 --> 00:25:42,202
The lower pair themselves
don't have the muscles to beat-down,
226
00:25:42,441 --> 00:25:45,965
but just enough strength to return up.
227
00:25:48,641 --> 00:25:54,719
A butterfly's overlapping wings, compared
to the size of their bodies, are enormous,
228
00:25:54,877 --> 00:25:58,972
around 10 times the size
of other insect wings.
229
00:26:09,003 --> 00:26:14,343
Because the wing is larger, each beat
can generate a huge amount of lift.
230
00:26:16,204 --> 00:26:21,969
So to stay airborne, a butterfly needs
to flap less often than other insects.
231
00:26:23,958 --> 00:26:30,870
But that slow wing-beat
also enables it to make rapid
and unpredictable changes of direction.
232
00:26:33,205 --> 00:26:37,475
And that allows butterflies to
fly in that zigzag, erratic way,
233
00:26:37,810 --> 00:26:41,445
which makes them so difficulty to catch,
if you're a butterfly collector,
234
00:26:41,578 --> 00:26:44,094
or more importantly, a predator.
235
00:27:02,748 --> 00:27:06,926
The combined front and hind wings
of a butterfly, not only constitute
236
00:27:07,013 --> 00:27:11,542
very effective flying mechanism,
they can also carry messages.
237
00:27:11,983 --> 00:27:16,361
In fact, they carry some
of the loveliest advertisements
in the whole of the animal kingdom.
238
00:27:16,715 --> 00:27:21,453
Like for example, this beautiful
Golden Birdwing butterfly from Borneo.
239
00:27:26,867 --> 00:27:31,029
The butterfly's huge wings
provide a spacious canvas
240
00:27:31,167 --> 00:27:34,962
on which they display
fantastically elaborate designs.
241
00:27:36,926 --> 00:27:40,542
So, how are these flying
advertisements created?
242
00:27:42,742 --> 00:27:47,507
The secret lies
in the microscopic structure
of the wing surface.
243
00:27:52,371 --> 00:27:56,568
These overlapping scales,
lined up like tiles on a roof,
244
00:27:56,761 --> 00:28:00,809
have evolved from bristles
that were once tiny sensors.
245
00:28:04,493 --> 00:28:09,186
Some contain tiny packets of pigment,
that give the wings colour.
246
00:28:17,277 --> 00:28:21,536
Others have a complex structure
which splits the light,
247
00:28:21,675 --> 00:28:27,201
so that when viewed
from a particular angle,
it reflects a brilliant iridescence.
248
00:28:40,046 --> 00:28:44,147
There are over 18,000 species
of butterfly around the world,
249
00:28:44,359 --> 00:28:48,658
and each has wings
with their own distinctive design.
250
00:28:50,004 --> 00:28:54,362
These ravishing colours
and delectable patterns, of course,
251
00:28:54,510 --> 00:28:57,990
enable a male butterfly
and a female butterfly, to know
252
00:28:58,146 --> 00:29:00,678
whether or not they belong
to the same species.
253
00:29:01,185 --> 00:29:04,600
And a mature adult ready to mate,
254
00:29:04,800 --> 00:29:09,051
can identify a suitable partner
from surprising distances.
255
00:29:17,784 --> 00:29:24,492
When a male and female eventually meet,
they flutter around each other
in a ritual dance.
256
00:29:27,032 --> 00:29:31,163
Each is checking out the flying skills
and wing-patterns of the other.
257
00:29:39,693 --> 00:29:42,568
If both pass the test, they mate.
258
00:29:52,828 --> 00:29:58,739
The sheer size of butterfly wings
might seem to condemn
their owners to a slow,
259
00:29:59,019 --> 00:30:01,519
almost dawdling flight.
260
00:30:02,246 --> 00:30:06,713
But they can be much more
efficient aeronauts,
than you might suppose.
261
00:30:08,881 --> 00:30:14,046
Butterflies may not be able
to fly very fast, but astonishingly,
262
00:30:14,172 --> 00:30:19,952
for such frail looking creatures,
they can travel for hundreds
of miles in search of food.
263
00:30:22,792 --> 00:30:28,070
New discoveries are revealing
that butterflies make immense journeys,
264
00:30:28,470 --> 00:30:30,934
and one of the most exciting
of these studies,
265
00:30:31,100 --> 00:30:36,538
is taking place 7,000 miles
west of Borneo, in Europe.
266
00:30:42,352 --> 00:30:46,142
I am joining a research project
in Central Spain,
267
00:30:46,348 --> 00:30:50,263
to look for one of the greatest
of all butterfly travellers.
268
00:30:52,113 --> 00:30:54,613
The Painted Lady.
269
00:30:58,267 --> 00:31:02,839
Every spring, Painted Ladies
appear in Spain in great numbers.
270
00:31:04,982 --> 00:31:07,810
But Spain is just a stopover.
271
00:31:11,336 --> 00:31:15,250
An international team of scientists
are uncovering evidence
272
00:31:15,322 --> 00:31:19,787
of an astonishing journey
right across Europe and beyond.
273
00:31:24,719 --> 00:31:30,722
This hugely ambitious project,
is the brainchild
of Dr. Constantise Stefanescu.
274
00:31:42,156 --> 00:31:45,944
Detailed records of when
and where Painted Ladies appear,
275
00:31:46,130 --> 00:31:49,776
have revealed an extraordinary
mass migration.
276
00:31:50,227 --> 00:31:54,937
We were able to collect
a huge number of observations
277
00:31:55,020 --> 00:31:58,541
from ah.. more than
60 different countries,
278
00:31:58,930 --> 00:32:04,861
and.. maybe 35,000 records...
- Really?
279
00:32:05,068 --> 00:32:08,927
..many people contributing
ah.. their observations,
280
00:32:09,363 --> 00:32:13,248
and for the first time
it was possible to understand
281
00:32:13,314 --> 00:32:17,269
the general pattern
of migration all around.
282
00:32:18,709 --> 00:32:23,266
By combining this wealth of data,
the team are revealing a route map
283
00:32:23,442 --> 00:32:25,942
that spans incredible distances.
284
00:32:27,034 --> 00:32:29,896
And it begins in North Africa.
285
00:32:31,693 --> 00:32:36,724
Large numbers of Painted Ladies
breed in Morocco over the winter,
286
00:32:37,524 --> 00:32:41,559
before setting out
across the Mediterranean to Europe.
287
00:32:42,008 --> 00:32:45,476
They then follow the spring bloom north,
as the plants
288
00:32:45,539 --> 00:32:49,914
that they and their young feed on,
sprout leaves and flowers.
289
00:32:50,866 --> 00:32:54,717
In summer, they appear
in Britain and Scandinavia.
290
00:32:56,499 --> 00:33:02,244
But no individual butterfly lives
long enough to achieve
this huge journey by itself.
291
00:33:02,685 --> 00:33:06,649
Each step is taken by a new generation.
292
00:33:09,835 --> 00:33:13,306
So, this Painted Lady in Britain
is the grandchild
293
00:33:13,389 --> 00:33:16,635
of a butterfly that set out from Morocco.
294
00:33:19,572 --> 00:33:23,576
But then, in autumn,
all the Painted Ladies vanish.
295
00:33:25,919 --> 00:33:31,129
Do they simply die out? Or could there be
a return leg to their epic migration?
296
00:33:33,701 --> 00:33:37,087
Searching for an answer to this mystery,
has given the project
297
00:33:37,181 --> 00:33:40,286
its most astonishing revelation yet.
298
00:33:41,770 --> 00:33:44,253
And it comes from a part
of the team based
299
00:33:44,301 --> 00:33:48,560
at Rothamsted Research Institute,
just outside London.
300
00:33:50,098 --> 00:33:55,957
The key discovery emerged
from a surprising source. Radar.
301
00:34:00,133 --> 00:34:05,620
Our radar has a vertical pointing beam,
and it illuminates a narrow column
of the sky above,
302
00:34:05,690 --> 00:34:08,193
like shining a powerful spotlight
up into the sky,
303
00:34:08,413 --> 00:34:12,358
and we're able
to detect individual insects
as they fly through that beam.
304
00:34:13,765 --> 00:34:18,499
The signal is so detailed,
it can even help identify the species.
305
00:34:20,304 --> 00:34:22,512
And during the autumn disappearance,
306
00:34:22,692 --> 00:34:26,190
the radar picked up large
numbers of Painted Ladies.
307
00:34:27,349 --> 00:34:30,499
They won't dying out,
they were on the move,
308
00:34:30,712 --> 00:34:33,841
and they were flying
at astonishing heights.
309
00:34:35,014 --> 00:34:38,225
What we found was that in fact
the Painted Ladies were highly abundant
310
00:34:38,303 --> 00:34:41,513
at heights of three, four, five
hundred metres above the ground.
311
00:34:45,083 --> 00:34:49,708
At this great height, they were
invisible to observers down below.
312
00:34:50,346 --> 00:34:52,846
This explained their disappearance.
313
00:34:53,879 --> 00:34:59,131
But the butterflies
had their own very good reasons
to travel at such altitudes.
314
00:35:00,938 --> 00:35:03,886
One of the benefits of flying
at three or four hundred metres
above the ground,
315
00:35:04,083 --> 00:35:06,977
is that the wind speeds there are much
faster than they are at ground level,
316
00:35:07,043 --> 00:35:09,938
so the insects are able to get
a lot of assistance from the wind,
317
00:35:10,018 --> 00:35:13,142
and travel much faster
than they would,
under their own powered flight,
318
00:35:13,321 --> 00:35:17,784
and we see these Painted Ladies
traveling at 50 or even 70 km an hour.
319
00:35:21,835 --> 00:35:25,000
As well as measuring
the phenomenal speed of their flight,
320
00:35:25,208 --> 00:35:28,107
the radar also revealed its direction.
321
00:35:28,621 --> 00:35:31,121
They were heading south.
322
00:35:32,677 --> 00:35:35,177
So where were they going?
323
00:35:36,771 --> 00:35:42,300
The astonishing answer came
from Constantise� far-flung
network of observers,
324
00:35:42,786 --> 00:35:46,549
and the crucial piece of data
was gathered in Africa.
325
00:35:47,076 --> 00:35:50,757
Some expeditions in Africa,
in October, November,
326
00:35:50,826 --> 00:35:55,543
have shown that there is a huge arrival
of butterflies at that moment.
- Really?
327
00:35:55,706 --> 00:36:00,908
So, by the end of the summer,
the newborn butterflies in Europe,
328
00:36:01,098 --> 00:36:04,890
start to migrate way back to Africa.
329
00:36:05,063 --> 00:36:07,563
Really?
- Yeah.
330
00:36:07,857 --> 00:36:13,729
A final generation riding
on high altitude winds
makes an immense journey
331
00:36:13,788 --> 00:36:18,925
of up to 3,000 miles to West Africa,
in just a matter of days.
332
00:36:22,301 --> 00:36:25,336
Observers on the ground,
and radar in the air,
333
00:36:25,502 --> 00:36:29,123
had found proof
of an amazing migration cycle.
334
00:36:30,517 --> 00:36:34,073
Just in one year the whole cycle is made,
335
00:36:34,464 --> 00:36:38,295
and is the succession
of these six generations moving about
336
00:36:38,692 --> 00:36:44,911
5,000 kilometres in one direction,
and 5,000 in another direction.
337
00:36:47,322 --> 00:36:50,153
This migration is in fact
the longest made by
338
00:36:50,238 --> 00:36:53,084
any insect on the planet
so far discovered.
339
00:36:54,240 --> 00:36:56,509
But that raised another question.
340
00:36:56,708 --> 00:37:00,581
How did each generation know
which direction in which to fly?
341
00:37:03,241 --> 00:37:07,142
The Rothamsted scientists once again
set out to find an answer,
342
00:37:08,446 --> 00:37:13,052
by tracking the behaviour
of Painted Ladies
much closer to the ground.
343
00:37:21,444 --> 00:37:23,944
This is our flight simulator experiment.
344
00:37:24,404 --> 00:37:28,404
What we are done is we've tethered
our butterflies to a very fine rod,
345
00:37:28,723 --> 00:37:31,378
and we've put them inside
these flight simulators.
346
00:37:31,540 --> 00:37:35,508
They are ridged up to the computer,
and the butterflies are free to turn.
347
00:37:35,931 --> 00:37:38,813
And as they're turning,
we're recording that turning,
348
00:37:39,010 --> 00:37:43,436
and we can actually draw out
the flight path that they would've taken
if they free flying.
349
00:37:46,230 --> 00:37:50,080
The barrel blocks the butterfly's view
of the surrounding scenery,
350
00:37:50,208 --> 00:37:52,884
removing any possible distractions.
351
00:37:53,874 --> 00:37:57,688
The only reference point they have,
is the sky above.
352
00:37:59,955 --> 00:38:04,747
Remarkably, the butterflies
consistently choose a common direction.
353
00:38:07,768 --> 00:38:12,695
These are the flight headings,
so each spot is one individual butterfly
354
00:38:12,935 --> 00:38:15,544
and the overall direction
that they went in.
355
00:38:16,062 --> 00:38:20,007
So you can see that on average
my butterflies were flying South.
356
00:38:21,359 --> 00:38:26,165
What we found, when we put the lid
on the simulator
so they couldn't see the sky,
357
00:38:26,493 --> 00:38:30,270
is, as you will see, they didn't know
which direction to go in,
358
00:38:30,367 --> 00:38:33,524
they weren't able to maintain
the southwards heading.
359
00:38:35,385 --> 00:38:38,930
Rebecca concluded that their ability
to choose this heading
360
00:38:39,094 --> 00:38:42,539
must depend on the one thing
they can see in the sky above:
361
00:38:43,572 --> 00:38:46,072
The sun.
362
00:38:47,661 --> 00:38:52,920
Actually the sun is a really good cue,
it's very predictable
in its movements across the sky,
363
00:38:53,281 --> 00:38:57,103
and butterflies will be flying
in the middle of the day when it's warm,
364
00:38:57,357 --> 00:39:02,895
when the sun is out, and the sun will be
in the south at that time of day.
365
00:39:03,074 --> 00:39:07,694
So that's a really clear cue
for the butterflies to know
which way is south.
366
00:39:11,035 --> 00:39:14,250
This inbuilt compass
allows Painted Ladies
367
00:39:14,344 --> 00:39:17,894
at high altitude, to select
a wind that's heading south,
368
00:39:18,282 --> 00:39:23,226
and so hitch a free ride
on the long return journey,
all the way to Africa.
369
00:39:31,126 --> 00:39:36,712
Some insects face
a very different challenge,
not flying long distances,
370
00:39:37,025 --> 00:39:39,525
but flying in the dark.
371
00:39:48,929 --> 00:39:54,416
A light trap can attract some
of the most remarkable
of these nocturnal flyers.
372
00:39:59,435 --> 00:40:01,935
Moths.
373
00:40:04,372 --> 00:40:08,821
Moths probably evolved to fly
at night to avoid predators.
374
00:40:10,457 --> 00:40:17,175
Their eyes are adapted to low light,
but they also use a second,
highly developed sense: Smell.
375
00:40:21,534 --> 00:40:24,993
This is a male Moon Moth.
376
00:40:26,228 --> 00:40:31,280
Moths overlap their two pairs of wings,
in just the same way as butterflies do,
377
00:40:31,848 --> 00:40:37,137
and this particular moth is very special.
It has an extremely short life.
378
00:40:37,299 --> 00:40:41,529
It will only live for a week.
It won't even feed.
379
00:40:42,160 --> 00:40:46,124
Its only object is to find a female.
380
00:40:46,645 --> 00:40:51,897
And it does that with these
remarkable feather-like antenna.
381
00:40:54,483 --> 00:40:58,562
The female emits a particular
characteristic scent,
382
00:40:58,816 --> 00:41:05,522
and with those antennae, the male can
sense it from as much as a mile away.
383
00:41:05,993 --> 00:41:12,855
He then takes-off and flies upwind,
until eventually it finds the source.
384
00:41:21,023 --> 00:41:26,471
Moths with their combined front and
rear wings, are also excellent flyers.
385
00:41:29,700 --> 00:41:34,257
Some live longer,
and so need to fly to find food.
386
00:41:35,452 --> 00:41:39,003
This Sphinx Moth's
favourite food, is nectar.
387
00:41:41,313 --> 00:41:44,153
It can even hover as it drinks.
388
00:41:53,823 --> 00:41:56,833
So by overlapping
their two pairs of wings,
389
00:41:57,299 --> 00:42:01,203
butterflies and moths
have become very competent flyers.
390
00:42:01,574 --> 00:42:05,417
But there's one group
of flying insects that has changed
391
00:42:05,693 --> 00:42:09,908
the back pair of wings
into something quite, quite different.
392
00:42:10,215 --> 00:42:16,567
Something that enables them to perform
the most extraordinary aerial gymnastics.
393
00:42:18,173 --> 00:42:22,986
For the final chapter
in our story of flying insects,
I'm returning to London.
394
00:42:30,013 --> 00:42:35,390
The urban jungle and
its human inhabitants,
provide plenty of shelter and food,
395
00:42:35,670 --> 00:42:40,216
for a particularly adaptable
and numerous kind of insect.
396
00:42:43,760 --> 00:42:46,260
Ah, thank you very much.
- Thank you.
397
00:42:48,730 --> 00:42:52,341
An inviting meal like this one,
will I'm quite sure,
398
00:42:52,418 --> 00:42:57,591
very soon attract a flying diner,
that is one of the most remarkable
399
00:42:57,775 --> 00:43:00,275
of all insect aeronauts.
400
00:43:02,888 --> 00:43:05,388
It is of course, a fly.
401
00:43:06,243 --> 00:43:10,684
This particular kind, a blow fly,
occurs all over the world,
402
00:43:11,365 --> 00:43:17,648
and its ancestors have been buzzing
around for a least 250 million years.
403
00:43:20,738 --> 00:43:25,606
Flies are so common, we tend
to dismiss them as just irritating pests,
404
00:43:26,021 --> 00:43:29,522
but their flying abilities
are truly remarkable.
405
00:43:30,170 --> 00:43:33,979
Watch what happen if I try
and swat this one with the menu.
406
00:43:39,385 --> 00:43:45,839
Slowing down the action by 40 times,
we can see how astonishingly
agile flies are.
407
00:43:50,809 --> 00:43:55,238
It makes its escape in the time
it takes me to blink my eye.
408
00:43:57,798 --> 00:44:02,765
The ability to twist and turn at such
high speeds, and so evade enemies,
409
00:44:03,000 --> 00:44:06,314
has made flies the global success
that they are.
410
00:44:13,660 --> 00:44:16,901
They are the jet fighters
of the insect world,
411
00:44:17,001 --> 00:44:20,812
and they owe their manoeuvrability
not to the shape of their wings,
412
00:44:21,008 --> 00:44:27,803
nor the power of their muscles, but to
a set of highly advanced flight sensors.
413
00:44:30,247 --> 00:44:35,053
A fly has its own version
of a fighter pilot's instrument panel,
414
00:44:38,261 --> 00:44:43,771
providing constant updates on speed,
altitude and direction of travel.
415
00:44:49,104 --> 00:44:52,260
A fly gathers this flight-data
through its eyes,
416
00:44:53,253 --> 00:44:56,211
and these are among the best
in the business.
417
00:44:58,019 --> 00:45:03,760
They can process visual information
around 10 times as fast as our own eyes.
418
00:45:05,032 --> 00:45:08,667
But in high speed manoeuvres,
even a fly's eyes
419
00:45:08,759 --> 00:45:12,746
struggle with one crucial
piece of flight data:
420
00:45:14,457 --> 00:45:18,554
The angle of its body in the air,
and the way it changes.
421
00:45:18,894 --> 00:45:24,244
Information that a human pilot would get
from an instrument based on a gyroscope.
422
00:45:26,853 --> 00:45:32,153
And that is essential if you going
to pull-off a stunt like this one.
423
00:45:40,666 --> 00:45:44,850
Fortunately, flies not only
have eyes to guide them.
424
00:45:45,631 --> 00:45:50,626
They also have a second, and even
more remarkable set of sensors.
425
00:45:51,014 --> 00:45:55,965
One that is derived
from that original four-wing design.
426
00:45:59,708 --> 00:46:03,002
A fly only has a single pair of wings.
427
00:46:07,079 --> 00:46:10,577
The rear pair have been
converted into something else.
428
00:46:11,786 --> 00:46:15,876
A tiny club-like appendage
known as a haltere.
429
00:46:17,564 --> 00:46:22,114
This surprisingly sophisticated organ,
alerts the fly to changes
430
00:46:22,196 --> 00:46:25,305
in the position of its body in the air.
431
00:46:27,772 --> 00:46:31,660
As the fly takes-off, each haltere
begins to beat up and down,
432
00:46:31,842 --> 00:46:35,378
and so fast, it immediately
becomes a blur.
433
00:46:38,899 --> 00:46:44,667
But in slow motion, we can see that it
swings back-and-forth like a pendulum.
434
00:46:46,875 --> 00:46:49,283
To understand how the haltere works,
435
00:46:49,386 --> 00:46:52,879
we need to track its movement
in a mid-air roll.
436
00:46:56,236 --> 00:47:00,478
The weighted tip of the haltere,
has a kind of moving inertia,
437
00:47:01,498 --> 00:47:06,421
so that it remains
on the same swinging path
as the fly banks.
438
00:47:07,390 --> 00:47:10,874
Now, the angle between the body
and the haltere changes,
439
00:47:10,962 --> 00:47:13,482
and the base is put under strain.
440
00:47:13,711 --> 00:47:17,493
This triggers sensors
which register the roll.
441
00:47:22,588 --> 00:47:28,314
The fly can then adjust
its wing beat to correct
any imbalance, however extreme.
442
00:47:31,800 --> 00:47:35,855
New studies into a second,
remarkable use of the haltere signal,
443
00:47:36,081 --> 00:47:39,197
are taking place
at London's Imperial College.
444
00:47:43,262 --> 00:47:48,310
In the department of Bioengineering,
experts are studying Blow Flies
445
00:47:48,459 --> 00:47:52,514
to see if their natural flight mechanics
can improve the performance
446
00:47:52,805 --> 00:47:55,856
of man-made flyers, like this drone.
447
00:47:59,282 --> 00:48:05,059
Flies are incredibly manoeuvrable,
and if you look at their performance,
448
00:48:05,166 --> 00:48:09,097
one chasing another one,
um.. it's really hardly
449
00:48:09,189 --> 00:48:12,894
any other animal that can match
this sort of aerodynamic performance.
450
00:48:13,634 --> 00:48:18,210
Holger has devised an experiment
to investigate an intriguing connection,
451
00:48:18,368 --> 00:48:23,848
between a fly's halteres and
its other key flight sensor, its eyes.
452
00:48:30,253 --> 00:48:35,230
A tiny motor simulates a series
of high speed mid-air rolls.
453
00:48:36,732 --> 00:48:40,862
The way the fly then reacts,
is recorded on a specialist camera
454
00:48:41,071 --> 00:48:44,052
which can replay
the action in slow motion.
455
00:48:47,311 --> 00:48:52,438
As you can see if you look closely,
the head of the fly is maintained level,
456
00:48:53,127 --> 00:48:56,668
the body is rotating,
and to maintain level gaze,
457
00:48:56,788 --> 00:48:59,572
they have to counter-rotate the head.
458
00:49:00,951 --> 00:49:06,125
Keeping the eyes level is vital,
if they're to gather
accurate flight information,
459
00:49:06,204 --> 00:49:11,447
and the halteres have been identified
as the crucial sensor,
that makes this possible.
460
00:49:11,996 --> 00:49:17,632
Visual system alone would
just be too slow, that's where
actually the halteres come in.
461
00:49:17,779 --> 00:49:21,644
The halteres are extremely fast
in terms of their responses,
462
00:49:21,902 --> 00:49:28,629
and their immediate.. well signals,
that are then sent to..
to the neck motor system,
463
00:49:28,696 --> 00:49:32,360
and to the flight motor system,
they are the first really
464
00:49:32,432 --> 00:49:36,364
to compensate for any disturbances,
and if that has happened,
465
00:49:36,871 --> 00:49:41,849
the visual system is perfectly well
situated to cope with the rest.
466
00:49:45,452 --> 00:49:51,296
So flies lost a pair of wings,
but gained an extraordinary
new flight sensor
467
00:49:51,416 --> 00:49:55,611
that made them the most advanced
flyers in the insect world.
468
00:50:02,491 --> 00:50:09,138
Flight has enabled the insects
as a whole, to become
an astonishing global success.
469
00:50:09,510 --> 00:50:12,079
There are twice as many insect species,
470
00:50:12,138 --> 00:50:15,547
then there are, of all
other animals put together.
471
00:50:16,416 --> 00:50:19,684
Theirs is a remarkable evolutionary story
472
00:50:19,879 --> 00:50:23,635
that spans over 320 million years.
473
00:50:24,995 --> 00:50:28,688
From the first four-winged creatures
that emerged from the water,
474
00:50:29,563 --> 00:50:34,611
to the armour-plated beetles
which colonise land away from water.
475
00:50:36,906 --> 00:50:40,216
The butterflies
with their huge colourful wings.
476
00:50:42,886 --> 00:50:47,468
And the stunningly skilful
aerobatic flies.
477
00:50:49,222 --> 00:50:54,609
But skill may not be enough,
sometimes sheer size counts.
478
00:50:55,068 --> 00:51:00,307
The insects had the skies for themselves,
for around 100 million years,
479
00:51:00,683 --> 00:51:06,169
but then a new group of animal appeared,
animals that could build bigger bodies,
480
00:51:06,398 --> 00:51:12,307
and they were to lift the techniques
of flying, to even greater heights.
481
00:51:14,670 --> 00:51:17,841
As our journey through time
continues, we encounter
482
00:51:17,940 --> 00:51:22,837
the extraordinary pioneers
of a new wave of larger flyers:
483
00:51:25,800 --> 00:51:28,696
Monstrous winged reptiles.
484
00:51:31,821 --> 00:51:38,029
Strange feathered dinosaurs, whose
ventures into the air led to the birds.
485
00:51:41,252 --> 00:51:45,576
And a group of mammals that conquered
the pitch-black of the night:
486
00:51:47,464 --> 00:51:49,964
The bats.47173
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