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A summer evening
on the Körös river in Central Europe.

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Its waters are mirror-smooth.

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But on this particular day of the year,
all that is about to change.

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Giant mayflies, Europe's largest,

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are starting to rise to the surface

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and struggle out of the skins
in which they lived as larvae.

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At first, they come in ones and twos.

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Soon there will be millions.

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For two years, they've lived underwater.
Now they must fly to find a mate.

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This should be the climax of their lives.

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The first to appear are quickly taken by predators.

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But soon the swarms are so huge

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that neither fish nor birds
can make any impact on them.

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The first mayflies to emerge
in this mass hatching on this river in Hungary

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are all males.

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As soon as they free themselves
from the larval skin on the surface,

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they take off and seek safety in the banks.

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And there they hang in trees and bushes,
or indeed on my finger.

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And the reason they have to rest like this

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is because they still have to make one final moult.

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Their wings that were transparent
now have a handsome blue tinge

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and the elegant filaments at the end
of their abdomens are even longer than before.

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They are looking for mates,
but they have a problem.

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They can't feed
for they have neither mouth nor stomach.

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They have to fuel their flight entirely
from the reserves of fat

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that they built up when they were larvae
feeding in the river.

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But that fat will only last them
for about half an hour of flight time.

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So the race to mate now becomes a frantic one.

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The females begin to rise to the surface

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and the males fly up and down the river
searching for them.

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As soon as they find one, they all pounce on her,

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competing to be the one to fertilise her eggs.

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But the struggle of doing so
saps their limited energy.

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Before long, they begin to run out of fuel

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and though they flutter despairingly,
they can't maintain themselves in the air.

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Win or lose, their lives are almost over

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and dead bodies
start to litter the surface of the water.

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But the females are still in the air.

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They're flying upstream,

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judging the depth of the river
and the currents in it

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to find a place where they can lay their eggs

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so that they will float back downriver
to the same sort of place

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where the adults themselves lived as larvae.

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The ancestral mayflies were among
the first creatures of any kind to take to the air

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about 320 million years ago.

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For them, as for their living descendents,
flight was a brief but invaluable way

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of finding a mate
and expanding their breeding territories.

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The river has also been the home
of another kind of insect

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with an equally ancient ancestry and it, too,
is beginning to emerge from the water.

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Bigger and more ferocious than the mayfly larvae,

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it has been feeding on tadpoles,
and even small fish.

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But that phase of its life is over.

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Now, each one has to haul itself
out of the water and into the air.

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On the top of its thorax,
it carries a bulging backpack.

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It hunches itself and its outer skin splits.

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A very different creature begins to appear.

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White threads are drawn out of its flanks.

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They're the linings of thin tubes
that penetrate deep into its body.

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Air tubes that will enable the insect to breathe
now that it is out of water.

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It gulps air, inflating its body,
forcing fluid into the bundle on its back.

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Its wings begin to unfurl.

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Ten minutes later, the wings open.

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They'll never close again.

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Next, the huge muscles within its thorax
must be exercised to prepare them for action.

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And it's away.

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Dragonflies, like mayflies,

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belong to the most ancient group of insects
that flew over the land.

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And here, in the museum in Harvard,

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there are fossils of them
that are 150 million years old.

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They're almost identical with
species that are still flying today.

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However, they are by no means the oldest.

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We know that there were
other dragonflies even earlier,

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225 million years ago,

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that were flying
through the Coal Measure swamps.

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We don't have complete specimens
of any of those,

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but there are some tantalising
and amazing fragments. And here's one.

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This marvellously preserved wing

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has very much the same pattern
of veins supporting panels of membrane

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as living species.

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The thing that makes it different is its size.

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From base to tip,
it measures 12 inches, 30 centimetres.

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Little imagination is needed to replace
the membrane that must have been there.

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This insect must have had a wingspan
as big as a seagull's.

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Vibrating these wings preparing for flight
must have been a formidable business.

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A creature this size must have been
at least 10 times heavier

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than the largest insect flying today.

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How did it manage to get into the air?

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One suggestion is that in those far-off times
there was much more oxygen in the air

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and that would have given the extra power needed
to beat these huge wings.

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But it's a fair guess
that this ancient pioneer of the skies

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flew with much the same technique
as dragonflies do today.

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Living dragonflies can reach speeds
of nearly 40 miles an hour

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and fly several miles
in their search for new territory.

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They're all aerial hunters,
relying on their supreme aeronautical skills

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to snatch their prey from the sky.

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Their great agility in the air
comes from being able

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to beat each of their two pairs of wings
quite independently.

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You can see clearly that they do this

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when the camera slows down the action
400 times.

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This one is coming in to its perch.

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Perfect control is essential
to make all the tiny adjustments needed

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for an accurate, pinpoint touchdown.

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All dragonflies, when they perch,
hold their wings outstretched.

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But they have close relations, damselflies,

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and they perch with their wings closed
above their backs.

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Mosquitoes stand little chance
when damsels go hunting.

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But flight for damsels,
as for dragonflies and mayflies,

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is primarily the means
to find a mate and to breed.

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And to do that they, like the others, need water.

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Flight is itself an important element
in their courtship.

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These blue males must first establish
a territory for themselves above open water.

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And that involves aerial jousts
that can last for hours.

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Mature females, whose wings in this species
are not blue but golden brown,

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are attracted to those males
who control good places for egg-laying.

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But the males must, nonetheless,
display the correct wing signals.

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This one, patrolling his territory,
is using a special flight

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to flaunt his handsome wings,
inviting females to join him.

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A female signals her willingness to consider
doing so with a flick of her wings.

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So now, he treats her to his full display.

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The female's tail-up posture is apparently a signal

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that declares that
she's not yet sufficiently impressed.

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Now it seems he's got it right.
Her tail is pointing downwards.

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He grabs the back of her neck
with the claspers at the end of his abdomen.

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She brings her abdomen forward

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to reach a chamber under his thorax
where he stores his sperm.

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His first action, though,
is to scour out her genital tract

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to remove any sperm that
might be there from a previous mating.

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Only when he's done that
will he inject his own sperm.

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And now he must show her the best places
in his territory for laying eggs.

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He flies up and down with his tail curled
and lands on a suitable piece of vegetation.

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The female settles down to lay,

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cutting slits in the plant stems with her ovipositor

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and inserting an egg into each one.

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She may lay as many as 30.

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And all the time the male keeps guard,
lest rival males should try to mate with her.

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In other damsel species, the males make sure
that no other male can reach their partners

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by keeping hold of them
throughout the whole process.

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The young that hatch from the eggs
of these insects, the larvae,

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look very unlike their parents.

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This is a dragonfly larva, and it's in this form
that dragonflies spend most of their lives.

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The larvae of both dragonfly and damselfly
are savage predators.

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They'll even feed on their own kind
if they get the chance.

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This particular larva has a very special problem.

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It's a cascade damsel and it has to snatch prey
that is swept past it by the rushing water.

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Cascade damsels are very rare and live around
just a few Central American waterfalls,

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like this one in the mountains of Costa Rica.

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The adult male has to perform his courtship flight
under very difficult conditions indeed.

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Somehow, he's able to fly
even when he's dripping wet.

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And he shows off to the females
by actually flying through the cascades of water.

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To be a good breeding territory,
the vertical rock surface

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has to be covered
by just the right amount of water.

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Too deep and prey may be out of reach.

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Too shallow and the larvae
could be picked off by birds.

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A female will only mate with a male
if she approves of his choice of territory.

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And this one, it seems, does.

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This is it.
And she carefully fixes her eggs to the rocks.

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But not all damsels need
great areas of open water for breeding.

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In the rainforests of Central America,
like this one here in Costa Rica,

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there's a damselfly
that has managed to break the link

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with open expanses of water like rivers and ponds.

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It's also one of the most spectacular members
of the entire family.

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The helicopter damselfly,

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the largest in the world,
with a wingspan of up to 20 centimetres.

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Males tend to frequent sunlit patches
where the females can see them easily.

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And they have a special lazy,
flapping way of flying

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that is, in itself, an invitation.

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But although helicopter damsels
can live away from rivers and streams...

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the females nonetheless
require a little water in which to lay their eggs.

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And there is just enough

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in this little hollow here.

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And with luck, she'll come down.

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And into the water they go.

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But these eggs have watertight casings

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so they can be laid in air.

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They are butterfly eggs.
The link with water has been broken.

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Butterflies fly in a very different way
from dragonflies.

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They overlap their two pairs of wings
so that they flap as a single pair.

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They can't fly as fast or as aerobatically
as dragonflies,

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but they, nonetheless, are tireless in their search
for the particular food that will suit their young.

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And in the case of the cabbage white,
that's cabbage.

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Now, on the surface of this cabbage leaf

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there's a patch of tiny little pillbox-shaped eggs.

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And when they hatch,
the baby caterpillars will emerge

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and make an instant meal of the greenery.

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And they are already stirring.

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But the first dish on the menu is not vegetables,

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it's the shells of their own egg capsules,

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protein-rich and far too nourishing to be wasted.

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That first course, however, doesn't last long.

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Now for the main dish, cabbage leaves.

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When cabbage plants are damaged,
their leaves release a smell,

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and that quite often attracts the attention
of a rather different insect.

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It's a tiny wasp called Cotesia.

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She, too, is trying to make sure that
her young have food immediately available.

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But they like living flesh

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so she injects her eggs
into the butterfly's caterpillars.

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She does this with such surgical precision

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that her victims are not mortally injured

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and they continue feeding
as if nothing had happened to them.

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But now, much of what the caterpillars
so laboriously gather

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goes to nourish the wasp grubs
that are developing within them.

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As the caterpillars grow, they shed their skins.

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They do so five times until, ultimately,

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they are 800 times heavier than they were
when they first hatched.

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This fully-grown caterpillar must now find shelter.

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A strand of silk trails behind it,

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silk with which it ties itself to a twig.

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00:21:51,790 --> 00:21:55,544
And here, over a couple of days,
it changes into a chrysalis.

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Those caterpillars that were injected
by the Cotesia wasp

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don't get that chance.

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The grubs within them are now emerging.

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00:22:23,150 --> 00:22:26,984
They, too, spin silk
which hardens to form a cocoon

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beneath the caterpillars' empty skin.

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00:22:34,710 --> 00:22:38,225
Inside, the wasp grubs
are transforming themselves

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and two weeks later, out come the adult wasps.

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A different future awaits the chrysalis.

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Within its shell, and over a similar two weeks,

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the caterpillar's body
has been broken down and reassembled

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00:23:12,110 --> 00:23:14,704
and now the adult is ready to emerge.

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Its wings,
like those of a newly emerged dragonfly,

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need pumping up with liquid.

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The creature that was once an egg,
then a caterpillar, then a chrysalis

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has attained its final incarnation.

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So another generation of cabbage whites

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set off to find good places for their young.

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With their fragile-looking wings
and apparently erratic flight,

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butterflies might not seem to be
the most powerful of flyers.

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But, in fact,
they are extremely accomplished aeronauts

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and they can fly hundreds of miles if necessary

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to find the food they need.

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Some butterflies use the power of flight
for another purpose.

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To escape bad weather.

233
00:24:31,030 --> 00:24:34,739
These lush subtropical valleys in southern Taiwan

234
00:24:34,830 --> 00:24:37,390
are warm and green all year round.

235
00:24:37,470 --> 00:24:41,588
And in winter, they're filled by
literally millions of butterflies.

236
00:24:53,470 --> 00:24:57,463
They've all come from the north
of this great island, 500 miles away,

237
00:24:57,550 --> 00:25:02,670
for there the cold weather has killed off the plants
on which they fed during the summer.

238
00:25:10,390 --> 00:25:14,463
In the mornings, they take off from their roosts
and head for the forest canopy

239
00:25:14,550 --> 00:25:17,223
to warm themselves in the rays of the rising sun.

240
00:25:19,390 --> 00:25:22,268
They have to conserve
as much energy as they can.

241
00:25:22,350 --> 00:25:26,343
So, instead of using their stores of fat
to warm themselves,

242
00:25:26,430 --> 00:25:28,785
they absorb the sun's heat.

243
00:25:35,750 --> 00:25:38,218
There are four species of crow butterflies here

244
00:25:38,310 --> 00:25:41,268
as well as two species of blue tiger butterflies,

245
00:25:41,350 --> 00:25:43,181
and all find enough food

246
00:25:43,270 --> 00:25:46,307
to sustain themselves
in these warm and fertile valleys.

247
00:25:48,750 --> 00:25:52,982
Butterflies feed on liquid,
nectar and the juices of rotting fruit,

248
00:25:53,070 --> 00:25:59,305
and to suck it up they have instead of jaws
an extraordinarily long but extremely thin tube.

249
00:26:09,310 --> 00:26:13,781
In a newly emerged butterfly,
this tube is in two pieces

250
00:26:13,870 --> 00:26:17,909
for it is, in fact,
a highly modified pair of mouthparts.

251
00:26:17,990 --> 00:26:20,663
Each half has its own muscles and nerve supply

252
00:26:20,750 --> 00:26:24,379
so that the whole unit
is fully moveable and controllable.

253
00:26:28,510 --> 00:26:31,183
As the young butterfly prepares for adult life,

254
00:26:31,270 --> 00:26:34,387
these two sections are zipped together
to form a tube,

255
00:26:34,470 --> 00:26:36,665
like a miniature drinking straw.

256
00:26:36,750 --> 00:26:39,787
A special fluid cements the two halves together.

257
00:26:41,310 --> 00:26:44,586
The tube is largely made
of a material called resilin

258
00:26:44,670 --> 00:26:48,424
which, when distorted,
springs back to its original shape.

259
00:26:48,510 --> 00:26:51,627
In this case, a spiral, like a watch spring.

260
00:26:51,710 --> 00:26:56,386
When the muscles within it contract,
it straightens into a long probe

261
00:26:56,470 --> 00:26:59,940
that the butterfly can then insert
deep into a flower.

262
00:27:14,150 --> 00:27:18,268
Butterflies and moths
have the largest of all insect wings

263
00:27:18,430 --> 00:27:22,309
and their great size means that they can be used
very effectively as billboards

264
00:27:22,390 --> 00:27:26,588
on which to display patterns
proclaiming the species of their owner.

265
00:27:27,630 --> 00:27:33,023
The patterns are produced by tiny scales
that cover the wings like tiles on a roof.

266
00:27:33,110 --> 00:27:36,625
Some have a microscopic structure
that refracts the light

267
00:27:36,710 --> 00:27:39,622
and gives the wing a brilliant iridescent shimmer.

268
00:27:41,230 --> 00:27:43,664
Others contain chemical pigments.

269
00:27:48,670 --> 00:27:50,786
With these lovely advertisements,

270
00:27:50,870 --> 00:27:55,022
a male butterfly displays for females
and warns off rivals.

271
00:28:00,510 --> 00:28:05,538
Vivid patterns and bright colours
are used to a much lesser degree by moths,

272
00:28:05,630 --> 00:28:09,987
for many are only active at night
when colours, of course, are not easily seen.

273
00:28:14,550 --> 00:28:17,587
Moths also feed primarily on nectar

274
00:28:17,670 --> 00:28:20,423
which they suck up
in the same way as butterflies do.

275
00:28:21,070 --> 00:28:24,142
But one moth manages to tap a food source

276
00:28:24,230 --> 00:28:26,505
no butterfly has yet exploited.

277
00:28:29,030 --> 00:28:31,339
It comes from lantern bugs

278
00:28:31,430 --> 00:28:34,945
which feed by drilling into the bark
of a tree with their proboscis

279
00:28:35,030 --> 00:28:37,021
and sucking out the sap.

280
00:28:37,110 --> 00:28:40,500
This contains a little protein, which the bug wants,

281
00:28:40,590 --> 00:28:43,707
but a lot of sugar, most of which it doesn't want.

282
00:28:43,790 --> 00:28:46,588
So it squirts out the sweet excess.

283
00:28:46,670 --> 00:28:50,140
And to make sure that this doesn't attract
ants that might attack it,

284
00:28:50,230 --> 00:28:53,108
it fires the droplets well away from the tree trunk

285
00:28:53,190 --> 00:28:56,899
with a tiny spring-loaded spatula
at the end of its abdomen.

286
00:29:06,230 --> 00:29:08,824
One enterprising species of moth

287
00:29:08,910 --> 00:29:11,822
regularly sits behind the bug all night

288
00:29:11,950 --> 00:29:15,226
with the curled tip of its proboscis
delicately placed

289
00:29:15,310 --> 00:29:17,540
in the stream of the droplets.

290
00:29:30,590 --> 00:29:35,027
As sugar water accumulates,
so the moth sucks it up.

291
00:29:44,030 --> 00:29:47,909
Most moths, however,
feed by the rather more laborious method

292
00:29:47,990 --> 00:29:50,220
of flying from flower to flower.

293
00:29:50,310 --> 00:29:54,861
A few, the busiest, do so not only at night
but during the day as well.

294
00:29:54,950 --> 00:29:56,861
These are the hawk moths

295
00:29:56,950 --> 00:30:00,499
and there are several species of them
gathering nectar from this buddleia bush

296
00:30:00,590 --> 00:30:02,546
in the south of France.

297
00:30:05,110 --> 00:30:10,025
This hawk moth can fly very fast indeed
when it wants to,

298
00:30:10,110 --> 00:30:13,341
but it can also hover, as it's doing now,

299
00:30:13,430 --> 00:30:17,218
to sip nectar from each one of these small flowers.

300
00:30:18,750 --> 00:30:21,583
Beating its wings as fast as this, of course,

301
00:30:21,670 --> 00:30:24,025
takes a great deal of energy.

302
00:30:24,110 --> 00:30:27,546
So these hawk moths have to spend
much of their day

303
00:30:27,630 --> 00:30:30,702
going from flower to flower sipping the nectar

304
00:30:30,790 --> 00:30:35,068
which is so rich in the carbohydrates
they need to power their flight.

305
00:30:39,950 --> 00:30:42,623
They have huge forward-pointing eyes

306
00:30:42,710 --> 00:30:45,941
that enable them to aim their proboscis
with such accuracy

307
00:30:46,030 --> 00:30:49,625
that it slips into the exact centre
of each tiny flower.

308
00:30:51,830 --> 00:30:55,061
With so many minute flowers
so closely bunched together,

309
00:30:55,150 --> 00:30:58,267
it would be easy for the moth to visit some twice.

310
00:30:58,350 --> 00:31:00,181
But that would waste energy.

311
00:31:00,270 --> 00:31:02,864
And if we mark each flower
as the moth drinks from it,

312
00:31:02,950 --> 00:31:06,829
it's clear that the moth
somehow or other never does this.

313
00:31:13,870 --> 00:31:17,465
Hummingbird hawk moths
have no difficulty in hovering.

314
00:31:19,270 --> 00:31:21,659
Bee hawks, however, have heavier bodies

315
00:31:21,750 --> 00:31:25,743
and they sometimes use their legs
to help support themselves as they work.

316
00:31:32,190 --> 00:31:34,988
Their need to keep drinking is so pressing

317
00:31:35,110 --> 00:31:39,581
that a female will continue to do that
even when the male with whom she's mating

318
00:31:39,670 --> 00:31:42,867
seems to be trying to fly in the opposite direction.

319
00:31:47,190 --> 00:31:50,978
The buddleia plant may be
a particular favourite of hawk moths,

320
00:31:51,070 --> 00:31:53,061
but it is, of course, a foreigner

321
00:31:53,150 --> 00:31:56,699
introduced into our gardens from China
in the 19th century.

322
00:31:57,230 --> 00:32:01,940
The hawk moth's original supplies of nectar
came from the flowers of the meadows

323
00:32:02,030 --> 00:32:05,625
and they still feed there,
alongside many other insects.

324
00:32:06,270 --> 00:32:07,862
This is a carpenter bee.

325
00:32:08,910 --> 00:32:12,823
Bees also have two pairs of wings,
but they're hooked together

326
00:32:12,910 --> 00:32:15,902
so, like those of butterflies, they operate as one.

327
00:32:19,550 --> 00:32:23,338
Bumblebees have
particularly large and heavy bodies

328
00:32:23,430 --> 00:32:26,547
and flight for them can be a real effort.

329
00:32:26,630 --> 00:32:30,145
That's particularly so in spring
when the mornings are cold

330
00:32:30,230 --> 00:32:33,779
and queen bumblebees are just emerging
from their winter sleep.

331
00:32:34,910 --> 00:32:37,868
It's only a few degrees above freezing,

332
00:32:37,950 --> 00:32:41,226
but a queen needs to get started early
to look for food.

333
00:32:42,590 --> 00:32:44,865
The thick, furry hairs on her body

334
00:32:44,950 --> 00:32:47,942
help to conserve
what heat she manages to generate.

335
00:32:49,630 --> 00:32:54,306
At the moment, she's only a few degrees
warmer than the surrounding vegetation

336
00:32:54,390 --> 00:32:56,745
as the thermal camera clearly shows.

337
00:32:56,830 --> 00:33:01,142
Her body is only marginally more pink
than the blue leaves and moss around her.

338
00:33:03,750 --> 00:33:07,026
But she has a special way
of warming up for flight.

339
00:33:10,070 --> 00:33:12,504
She can put her wings out of gear

340
00:33:12,630 --> 00:33:16,703
so that without moving them
she can rev up the wing muscles inside.

341
00:33:16,790 --> 00:33:21,989
And that raises the temperature within her thorax
by 20 degrees centigrade or even more,

342
00:33:22,070 --> 00:33:25,904
as the expanding yellow image
on the thermal camera indicates.

343
00:33:36,670 --> 00:33:40,140
Her body temperature
is now over 30 degrees centigrade.

344
00:33:40,470 --> 00:33:43,189
At last, she has a chance of liftoff.

345
00:33:56,670 --> 00:33:59,503
She will now be able to visit the spring flowers

346
00:33:59,590 --> 00:34:02,582
while it's still too cold for others to do so.

347
00:34:18,670 --> 00:34:22,265
The long trumpets of the daffodils
retain heat very well

348
00:34:22,350 --> 00:34:26,662
and they're still warm
even after their hot-bodied visitors have left.

349
00:34:34,030 --> 00:34:39,150
Flies, back in their distant evolutionary past,
also had two pairs of wings.

350
00:34:39,230 --> 00:34:40,982
But their back pair

351
00:34:41,070 --> 00:34:44,426
have been reduced to simple knob-ended rods.

352
00:34:46,390 --> 00:34:49,427
These are particularly long on crane flies.

353
00:34:49,510 --> 00:34:52,946
They are part of the fly's flight instrumentation.

354
00:34:53,030 --> 00:34:56,147
Microscopic sensors
on their upper and lower surfaces

355
00:34:56,230 --> 00:35:01,258
tell their owner about the air currents
around its body and so help in flight control.

356
00:35:01,350 --> 00:35:03,784
They start up even before takeoff.

357
00:35:10,390 --> 00:35:15,180
Flies are such accomplished flyers
that they can land upside down on a ceiling

358
00:35:15,270 --> 00:35:18,068
or, in this case, the underside of a twig.

359
00:35:30,270 --> 00:35:34,104
Only when you slow down a fly's flight,
here by 100 times,

360
00:35:34,190 --> 00:35:38,024
can you fully appreciate
what superb aerial control they have.

361
00:35:46,510 --> 00:35:49,388
Some species, like these long-legged flies,

362
00:35:49,470 --> 00:35:52,746
flaunt their wings in courtship
just as damselflies do.

363
00:36:02,950 --> 00:36:06,181
These dance flies are voracious hunters

364
00:36:06,270 --> 00:36:10,468
and it's particularly important for them
that they perform their dance correctly.

365
00:36:10,550 --> 00:36:14,338
If one doesn't get it right,
its partner might well eat it.

366
00:36:41,510 --> 00:36:45,264
This performance, however,
seems to have been up to standard.

367
00:37:11,030 --> 00:37:12,543
For hover flies,

368
00:37:12,630 --> 00:37:16,145
arguably the most accomplished
of all insect aviators,

369
00:37:16,230 --> 00:37:21,145
immaculate aerial control
is what makes a male attractive to a female.

370
00:37:23,310 --> 00:37:29,180
A male lays claim to a mating territory by trying
to stay in exactly the same position in space

371
00:37:29,270 --> 00:37:31,181
for as long as possible.

372
00:37:31,270 --> 00:37:32,498
That's not easy

373
00:37:32,590 --> 00:37:36,663
when there are others all around you
trying to do precisely the same thing.

374
00:37:37,350 --> 00:37:41,628
It might seem that he's absolutely motionless.

375
00:37:42,630 --> 00:37:48,182
But, in fact, he's having to make continual
changes to adjust for slight currents in the air.

376
00:37:48,270 --> 00:37:51,262
It's an amazing piece of acrobatics,

377
00:37:51,350 --> 00:37:56,982
far better than anything
that we could do in a helicopter...

378
00:37:57,830 --> 00:38:02,221
and it's all done in order to impress the female,

379
00:38:02,310 --> 00:38:07,509
to show her
that he is superb at holding his territory.

380
00:38:13,070 --> 00:38:18,144
Having to chase away rivals that come too close
is an exhausting business.

381
00:38:18,230 --> 00:38:21,620
And when you're trying to maintain your hold
on a particular point in midair,

382
00:38:21,710 --> 00:38:24,508
even a small midge has to be chased away.

383
00:38:33,030 --> 00:38:35,021
After a morning spent doing this,

384
00:38:35,110 --> 00:38:38,989
a male hover fly may have lost
as much as a third of his body weight.

385
00:38:39,070 --> 00:38:43,939
Little wonder that he takes a break at midday
in order to rest and refuel.

386
00:38:45,310 --> 00:38:49,223
He dabs up nectar with mouthparts
that are shaped like a pad.

387
00:38:59,670 --> 00:39:02,025
Having refilled his fuel tank,

388
00:39:02,110 --> 00:39:06,308
the male returns to his territory
for the afternoon session of hovering

389
00:39:06,390 --> 00:39:10,383
in the hope of attracting yet another female
and mating with her.

390
00:39:15,430 --> 00:39:18,581
Once again, with his superb eyesight,

391
00:39:18,670 --> 00:39:22,822
he's ready to spot anything
that might whizz by him at high speed

392
00:39:22,910 --> 00:39:24,628
who could be a female.

393
00:39:24,710 --> 00:39:28,225
And I might just be able to fool him
with a peashooter.

394
00:40:08,870 --> 00:40:14,263
Although there may seem to be an extraordinarily
large number of different flies in the world,

395
00:40:14,350 --> 00:40:18,821
it's actually the beetles
that are the most varied of all insect groups.

396
00:40:19,710 --> 00:40:22,986
There are 300,000 species of them.

397
00:40:23,070 --> 00:40:26,779
Most find their food
by crawling and burrowing on the ground.

398
00:40:26,870 --> 00:40:29,987
And to prevent their wings
from being damaged in the process,

399
00:40:30,070 --> 00:40:33,540
they've turned the front pair
into protective shields.

400
00:40:34,270 --> 00:40:38,058
Some, like weevils,
keep their wing covers permanently closed

401
00:40:38,150 --> 00:40:42,382
and before takeoff,
push their functional wings out of special slits.

402
00:40:44,390 --> 00:40:48,349
Ladybirds, like most other beetles,
raise their wing covers

403
00:40:48,430 --> 00:40:51,786
and hold them clear of the hind wings
throughout their flight.

404
00:40:51,870 --> 00:40:57,627
The result could hardly be called aerodynamic
and consequently their flight is rather lumbering.

405
00:41:03,070 --> 00:41:05,823
Blister beetles are scarcely any better.

406
00:41:12,350 --> 00:41:16,502
When a flight is over, their hind wings
have to be packed away beneath the covers,

407
00:41:16,590 --> 00:41:18,546
a process that can be so complex

408
00:41:18,630 --> 00:41:23,067
that it demands all the skills
of a Japanese master of origami.

409
00:41:40,390 --> 00:41:44,065
With flight playing a relatively small part
in their lives,

410
00:41:44,150 --> 00:41:46,584
many beetles have grown very large.

411
00:41:46,670 --> 00:41:50,219
This one, the titan beetle
that lives in the forests of the Amazon,

412
00:41:50,310 --> 00:41:53,461
is almost certainly the biggest of all insects.

413
00:41:57,510 --> 00:42:00,149
I have to handle him with considerable care

414
00:42:00,230 --> 00:42:05,429
because those huge mandibles at the front
are powerful enough, it's said,

415
00:42:05,510 --> 00:42:08,547
to be able to cut straight through a pencil.

416
00:42:09,470 --> 00:42:13,748
He can fly,
but he can't get into the air from the ground.

417
00:42:13,870 --> 00:42:15,588
He's too heavy to do that

418
00:42:15,670 --> 00:42:19,629
so he has to climb trees
and launch himself into the air that way.

419
00:42:19,710 --> 00:42:24,579
And that's why he's got such powerful legs
armed with sharp claws.

420
00:42:25,430 --> 00:42:30,140
The titan is now known
to be the biggest of all beetles.

421
00:42:30,230 --> 00:42:35,987
The champion is seven inches long from the tip
of the mandibles to the tip of his abdomen.

422
00:42:36,830 --> 00:42:41,346
The larva of this great monster
has not yet been found.

423
00:42:41,710 --> 00:42:46,386
But it must be at least twice as big as the beetle,
a really huge grub.

424
00:42:47,790 --> 00:42:52,500
Beetles and many other insects
spend so much of their lives as flightless larvae,

425
00:42:52,590 --> 00:42:57,266
that it would be more accurate to think of them
as creatures of the earth rather than the sky.

426
00:42:58,070 --> 00:43:00,379
Flight for them, as it is for the mayflies,

427
00:43:00,470 --> 00:43:03,030
is a relatively brief episode
at the end of their lives.

428
00:43:04,590 --> 00:43:10,142
These cicadas in the eastern United States
spend 17 whole years below ground,

429
00:43:10,230 --> 00:43:12,300
sucking sap from tree roots.

430
00:43:12,390 --> 00:43:16,508
And then, within a few days,
a whole population emerges.

431
00:43:31,990 --> 00:43:35,744
There may be millions of them
in a single acre of land.

432
00:43:43,710 --> 00:43:48,022
They clamber up the trees
whose roots have provided them with sap

433
00:43:48,110 --> 00:43:50,624
for all of those 17 years.

434
00:44:08,230 --> 00:44:12,143
And here they change into their adult costume.

435
00:44:36,470 --> 00:44:40,986
Now they have the wings they need
to search for a partner.

436
00:44:44,270 --> 00:44:48,627
Empty larval cases
cover the tree trunks and the ground beneath.

437
00:44:51,550 --> 00:44:53,666
(CICADAS SINGING)

438
00:44:53,750 --> 00:44:58,505
And above, from the branches,
the millions have started to sing.

439
00:44:58,870 --> 00:45:01,259
The noise is ear-splitting.

440
00:45:06,830 --> 00:45:09,185
(SCREECHING SINGING)

441
00:45:17,470 --> 00:45:20,587
After 17 years of living underground,

442
00:45:20,670 --> 00:45:25,141
the cicadas are now approaching
the climax of their lives,

443
00:45:25,230 --> 00:45:28,188
and for the males, that means this.

444
00:45:34,430 --> 00:45:37,786
The call is his way of attracting a female.

445
00:45:45,830 --> 00:45:49,379
The females reply with a quite different sound.

446
00:45:50,510 --> 00:45:51,784
(CLICKING)

447
00:45:53,270 --> 00:45:56,740
A click made by flicking her wings.

448
00:45:56,830 --> 00:45:59,947
So, that's what the males are listening out for.

449
00:46:00,110 --> 00:46:05,468
I can imitate the female's wing flip
with a snap of my fingers

450
00:46:05,550 --> 00:46:08,622
and that causes them to follow me anywhere

451
00:46:08,710 --> 00:46:12,385
because they are so determined to find a female.

452
00:46:27,790 --> 00:46:29,781
Now, can I bring you back?

453
00:46:33,870 --> 00:46:35,906
How about coming this way?

454
00:46:45,150 --> 00:46:47,220
Oh, the noise is awful.

455
00:46:48,430 --> 00:46:50,341
Come this way. Come on.

456
00:46:51,030 --> 00:46:53,021
Yes, I can hear you.

457
00:46:54,670 --> 00:46:56,103
(GROANING)

458
00:46:56,750 --> 00:46:58,069
Quite right.

459
00:47:00,390 --> 00:47:03,109
At last, a male finds his partner.

460
00:47:03,190 --> 00:47:06,227
And as he does so, his call alters.

461
00:47:08,830 --> 00:47:12,664
He's indicating to her that after 17 years,

462
00:47:12,750 --> 00:47:15,742
the time has come to get down to business.

463
00:47:31,390 --> 00:47:36,145
How do these cicadas all emerge simultaneously

464
00:47:36,230 --> 00:47:38,425
after 17 long years?

465
00:47:39,070 --> 00:47:44,383
Well, we know that they can appreciate changes
in the contents of tree sap

466
00:47:44,470 --> 00:47:47,667
so they are able to detect the passing of a year.

467
00:47:48,110 --> 00:47:50,863
But how do they count up to 17?

468
00:47:50,950 --> 00:47:52,941
We have no idea.

469
00:47:53,030 --> 00:47:54,782
But even if we did,

470
00:47:54,870 --> 00:47:58,499
this surely would remain
one of the most astonishing,

471
00:47:58,590 --> 00:48:01,582
amazing events in the insect world.

472
00:48:01,670 --> 00:48:06,664
And it will all be over in a couple of weeks
for another 17 years.