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You might think
that the lights above my head are stars,

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but they can't be because I'm in a cave.

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Each one of those tiny lights

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is produced by the larva
of a small insect called a fungus gnat

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as a way of attracting its prey.

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The result is a display

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that must surely rank
as one of the most magical illuminations

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in the whole of the natural world.

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But shine a light sideways across the ceiling...

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then you can see that each little blue lamp

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is surrounded
by a curtain of glistening, beaded filaments,

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curtains that are invisible at other times.

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They're lures, and they can be lethal.

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Insects, hatching in the water below,

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fly up towards these tiny lights.

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And here, they are trapped by threads
of this extraordinary material

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that is the unique possession of the invertebrates.

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This is silk.

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This astonishing cave is near the small town
of Waitomo in New Zealand.

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Each light comes from the back end of a larva

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as it lies in a transparent tube of mucus

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slung from the ceiling by silken threads.

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And it's produced by phosphorescent chemicals

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in a special compartment
opening from the side of its intestine.

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The silk comes from glands at the other end,

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inside the larva's mouth.

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The larvae move around.

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They fix a silk thread to the rock

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and slowly inch their way over the ceiling
along a network of threads.

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Arriving in a new position,
the larva produces more silk,

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but this time it allows the thread
to dangle downwards.

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As each section emerges from its mouth,

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the larva, with a gulp, adds a blob of glue.

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Eventually, a single strand may be a metre long.

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There can be several hundred larvae
in a single square metre of cave roof

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and they all work hard
producing strand after strand.

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The more they make,
the greater their chances of catching something.

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Below, mayfly are hatching from the stream
that runs through the cave.

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They've been carried in here
by the current from outside as larvae.

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Now, they must look for a mate.

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But they find the blue lights above irresistible.

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And they're caught.

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The fungus gnat detects its victim's struggles

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from lines that run between the threads.

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Having made a capture, it turns off its light.

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That saves energy.

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Laboriously, it makes its way across to the thread
from which the vibrations are coming.

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It hauls it up and eats what's hanging on the end.

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It also eats the filament.

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That saves silk.

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This wonderful hunting technique

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is just one of an enormous number
of varied ways in which animals use silk.

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Silk really is an extraordinary material.

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It's stronger than a steel thread
of the same diameter

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and, unlike steel, it's elastic.

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It can stretch up to twice its length.

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The inhabitants of the undergrowth

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developed the ability
to produce this marvellous material

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very early in their evolutionary history,

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over 300 million years ago.

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At first, it seems they used it
in a very simple way, as an adhesive.

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And lacewings still do.

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Though for them,
it's an adhesive with a difference.

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This is a female.

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She is looking for a safe place to deposit her eggs.

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Silk will provide it

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but not exactly in the way you might think.

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She will lay up to 300 eggs,
almost twice her body weight.

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However, there are plenty of other insects around
that will eat those eggs

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if they find them.

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So she doesn't glue them
directly on the plant stem.

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First, she produces a little drop of sticky silk

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and then, at the end of that, the egg.

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It's suspended safely in midair.

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The silk is produced by glands in her abdomen
in liquid form.

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It's the very act of pulling it out
that changes it from liquid to solid.

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And that is true for all invertebrate silk.

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She will lay up to 30 eggs a day,

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each on its own stalk.

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That silken thread is so incredibly fine

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that insect predators like these ants
walk right by the eggs

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without realising that there is a tasty meal
within millimetres of them.

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So, despite regular ant patrols in search of food,

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the lacewing's eggs remain undiscovered.

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After three days, they begin to hatch.

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Now, at least, if danger threatens,

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her offspring will be able to help themselves

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by running away.

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In the lush rainforest of Trinidad,

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you can find sheets of silk wrapped around trees.

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Here it's also used for protection

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but by a quite different creature
in a quite different way.

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The manufacturers, a little-known group of insects
called web spinners,

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live beneath.

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They graze on algae and lichens
hidden by the sheets immediately above them.

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They produce their silk
not from their abdomens or their mouths,

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but from glands in their forelegs.

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Each leg has about 150 tiny silk ejectors

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which, between them, create a thin silken tissue.

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An ant in search of prey

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strolls over the surface
of the web spinners' marquee,

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but the silk sheet, thin though it is,
is impervious to smells

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and as long as the web spinner
doesn't move too much,

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the ant will be unaware of it,
a millimetre beneath its feet.

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(THUNDER RUMBLING)

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And the tent, like any decent tent, is waterproof.

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In fact, the tent is so waterproof

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that the web spinners beneath
are in danger of not getting enough water.

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So after the storm is over,

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they bite holes in places
where a little rain has accumulated

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and drink the tiny puddle dry.

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Of course, the hole has to be repaired
after a drink,

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but that's easy enough when you have
an almost limitless supply of silk in your legs.

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Of all the inhabitants of the undergrowth
that have exploited silk,

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none have done so with more variety and skill
than the spiders.

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And this is almost certainly the first way
in which they used it.

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Here on this bank in the Malaysian rainforest,

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there are strands of silk radiating
from this little patch in the middle.

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Watch what happens if I touch one of them.

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(EXCLAIMING)

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I can't help jumping.

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That was a trapdoor spider

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and it was so swift that you hardly saw it.

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Let's see if I can get it to do it again.

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The spider, when hungry,
sits close behind the trapdoor.

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The strands outside are all connected
to a silken collar

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that surrounds the mouth of the hole.

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Each of her feet is in contact with it.

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The slightest twitch is enough to tell her
that something's moving around outside.

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A single twitch will produce no reaction.

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That could be caused by a falling leaf
or a drop of water,

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but a repeated vibration,
especially if it moves from one strand to another,

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could mean prey.

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Prey like this beetle.

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Got it!

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Now, it will kill it.

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This is the most ancient of living spiders.

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The fact that it has uniquely segmented plates
on its back

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shows that it's more closely related than any other

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to those pioneer hunters, the scorpions.

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And, like them, it has a powerful venom.

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Once bitten, its victim has little chance.

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Trip lines were one of the earliest
of the spiders' hunting techniques,

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but other, later spiders,

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used silk to build
much more sophisticated structures.

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Orb webs are so familiar to us

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that we tend to forget
what complex structures they are.

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A single one can contain
up to 60 metres of silk of up to six different kinds

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and involve 3,000 separate attachments.

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And, what's more, some orb web spiders
spin a different one every night.

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The biggest and best webs are made,
in most species, by the female.

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She has to start by bridging the gap
across which she's to hang her web.

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The faintest breeze will catch a filament
as she spins it

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and carry it away into space.

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With luck, it will catch on a suitable anchor point.

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There!

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She runs across the filament,
trailing a line of much thicker, stronger silk

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and ties it off.

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Then she goes back to the middle of this line

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and drops down another.

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And she tightens it.

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The junction at the top
becomes the hub of the web

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to which she will attach radiating spokes.

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These must be particularly strong

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for the shape of the whole structure
depends on them.

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Once they're complete, she adds a spiral,

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working from the middle outwards.

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This first spiral is quite widely spaced
because it's only temporary.

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It will serve as a scaffolding, along which she runs

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to add a stronger, stickier
and more closely spaced spiral.

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That's this one.

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As the filament for this
emerges from her spinneret,

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she coats it with glue from separate glands
in her abdomen.

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After completing one section,
she eats the scaffolding line.

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It has no further use and it saves valuable silk.

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At first, this glue is evenly spread,

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but each time she fixes a section,
she twangs it with her leg

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so that it breaks up and forms a line of droplets.

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She can complete the whole intricate,
elegantly symmetrical structure

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in about an hour.

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When an insect strikes the web,

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the capture spiral stretches
and then retracts to its former size

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00:17:05,926 --> 00:17:09,601
without distorting its shape
and without such a severe recoil

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that the insect might be catapulted off again.

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00:17:14,286 --> 00:17:16,754
The beads of glue are the key.

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00:17:16,846 --> 00:17:19,201
Tension on the surface of a droplet

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hauls any slack into it.

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00:17:23,486 --> 00:17:28,321
When the insect hits,
it pulls out the coils of thread in each droplet,

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slowing the insect to a momentary standstill.

190
00:17:33,846 --> 00:17:38,795
And then the surface tension
pulls the silk back into each drop.

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00:17:41,846 --> 00:17:44,565
So the spiral thread doesn't break

192
00:17:44,646 --> 00:17:47,604
and the web as a whole regains its symmetry.

193
00:17:50,606 --> 00:17:53,916
The spider sits
with her legs resting on the spokes.

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00:17:55,726 --> 00:17:59,275
Any vibration on them will travel up her leg

195
00:17:59,366 --> 00:18:02,915
and be received by a small sense organ
in the joint.

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00:18:03,886 --> 00:18:09,085
This is covered with microscopic slits,
which are distorted by the slightest movement.

197
00:18:09,606 --> 00:18:13,281
So the spider is immediately aware
of the tiniest tremor.

198
00:18:13,766 --> 00:18:17,441
Once alerted, she pulls
on neighbouring spokes of the web

199
00:18:17,526 --> 00:18:22,600
to assess exactly in what direction
and how far away the signals originate.

200
00:18:34,486 --> 00:18:37,796
The fly is on the verge of breaking loose.

201
00:18:39,166 --> 00:18:40,519
Here she comes.

202
00:18:40,606 --> 00:18:43,962
She isn't hindered by the glue
she put on the capture spiral

203
00:18:44,046 --> 00:18:47,163
because her feet are coated with a special oil.

204
00:19:03,806 --> 00:19:06,081
Once her victim is in her grasp,

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00:19:06,166 --> 00:19:08,680
she produces yet another kind of silk.

206
00:19:08,766 --> 00:19:12,725
It emerges as a sheet
from a group of minute spigots.

207
00:19:12,806 --> 00:19:15,684
This is a fuzzy silk that's used for wrapping

208
00:19:15,766 --> 00:19:19,202
and, at moments like this, as a shroud.

209
00:19:33,726 --> 00:19:37,685
The biggest and strongest webs
are those made by Nephila,

210
00:19:37,766 --> 00:19:41,361
the golden orb web spider of the tropics.

211
00:19:41,446 --> 00:19:43,482
They may be several metres across

212
00:19:43,566 --> 00:19:46,683
and they're strong enough to catch small birds.

213
00:19:49,566 --> 00:19:52,034
This time, only a moth.

214
00:19:54,166 --> 00:19:58,796
After a killing bite,
she returns to the hub of her web to wrap it up.

215
00:20:00,646 --> 00:20:03,240
But big webs bring problems.

216
00:20:03,326 --> 00:20:07,160
It's not easy to control
what happens on their outer regions.

217
00:20:08,606 --> 00:20:10,642
This is Argyrodes.

218
00:20:10,726 --> 00:20:13,240
She's only one-hundredth the weight of Nephila

219
00:20:13,326 --> 00:20:16,875
so she can move across this huge web undetected.

220
00:20:16,966 --> 00:20:18,638
And she's a thief.

221
00:20:21,926 --> 00:20:24,724
A fly has arrived not far from her.

222
00:20:24,806 --> 00:20:27,081
She has a chance to steal it.

223
00:20:35,326 --> 00:20:38,443
But Nephila has also detected its arrival...

224
00:20:40,766 --> 00:20:43,678
and claims it without much difficulty.

225
00:20:54,006 --> 00:20:56,600
Another fly is caught in the web.

226
00:20:58,206 --> 00:21:00,800
Argyrodes now stands a better chance

227
00:21:00,886 --> 00:21:03,195
since Nephila is busy feeding.

228
00:21:04,206 --> 00:21:07,278
She cuts the filaments
between the fly and Nephila

229
00:21:07,366 --> 00:21:11,200
so that vibrations made by its struggles
won't reach her.

230
00:21:33,326 --> 00:21:36,204
Nephila, sitting at the hub of the web,

231
00:21:36,286 --> 00:21:39,995
seems quite unaware
of what's going on at its outer margin.

232
00:21:41,406 --> 00:21:44,364
The fly is now hanging from a single thread,

233
00:21:44,446 --> 00:21:48,803
but it's five times the weight of Argyrodes
and too heavy for her to carry.

234
00:21:48,886 --> 00:21:50,956
She has to be clever.

235
00:21:51,046 --> 00:21:52,923
She attaches a thread to it

236
00:21:53,006 --> 00:21:55,998
and runs it up to a twig outside the web.

237
00:22:04,526 --> 00:22:07,404
Nephila is still occupied with her meal.

238
00:22:10,286 --> 00:22:12,641
Another line, just to make sure.

239
00:22:27,126 --> 00:22:31,756
Now she can snip the last filaments
of the web and haul it away.

240
00:22:47,326 --> 00:22:49,886
Safely off Nephila's web at last,

241
00:22:49,966 --> 00:22:53,754
Argyrodes can enjoy her stolen meal in safety.

242
00:22:58,166 --> 00:22:59,997
(CHURCH BELLS TOLLING)

243
00:23:01,406 --> 00:23:03,203
For all its complexity,

244
00:23:03,286 --> 00:23:08,280
the orb web was one of the first kind
of silken traps devised by spiders.

245
00:23:08,846 --> 00:23:14,364
Subsequently, other species modified it
in some quite extraordinary ways.

246
00:23:15,646 --> 00:23:18,763
There's a web in this yew tree that's triangular.

247
00:23:18,846 --> 00:23:20,996
A slice, as it were, from an orb.

248
00:23:21,086 --> 00:23:23,122
It's made by Hyptiotes

249
00:23:23,206 --> 00:23:26,915
and her body forms an essential link
in its mooring cable.

250
00:23:27,446 --> 00:23:30,916
To be effective, the web has to be very taut.

251
00:23:33,286 --> 00:23:35,925
Hyptiotes ratchets up the tension

252
00:23:36,006 --> 00:23:39,840
by hauling in the main cable
and coiling it above her body.

253
00:23:45,646 --> 00:23:46,965
Tighter.

254
00:23:51,566 --> 00:23:52,794
Tighter.

255
00:24:00,126 --> 00:24:02,959
And that's about as tight as it will go.

256
00:24:04,286 --> 00:24:06,481
Now she has to wait.

257
00:24:06,566 --> 00:24:10,115
Flies can sometimes
disentangle themselves from a web

258
00:24:10,206 --> 00:24:12,766
if the spider doesn't grab them quickly,

259
00:24:12,846 --> 00:24:16,361
but a fly hitting this web won't get that chance.

260
00:24:19,926 --> 00:24:22,998
A strike triggers an instant reaction.

261
00:24:24,286 --> 00:24:26,720
In slow motion, you can see what happens.

262
00:24:26,806 --> 00:24:31,721
Hyptiotes immediately lets go of the coil
she was holding over her back.

263
00:24:33,126 --> 00:24:35,686
That causes her web to collapse

264
00:24:35,766 --> 00:24:38,803
and almost instantaneously entangle the prey.

265
00:24:44,086 --> 00:24:48,364
Few flies that hit a Hyptiotes web
manage to escape.

266
00:24:53,366 --> 00:24:56,164
The gladiator spider makes her web

267
00:24:56,246 --> 00:24:59,841
from a very special kind of multi-strand silk,

268
00:24:59,926 --> 00:25:02,394
which she backcombs to make fuzzy.

269
00:25:03,046 --> 00:25:08,166
She carefully attaches this
to a framework of ordinary un-fuzzy filaments.

270
00:25:16,206 --> 00:25:18,515
The fuzzy silk doesn't have glue on it,

271
00:25:18,606 --> 00:25:21,166
but it will entangle hairy legs.

272
00:25:24,926 --> 00:25:27,884
And it's also extremely elastic,

273
00:25:27,966 --> 00:25:30,161
which is crucially important.

274
00:25:45,086 --> 00:25:46,883
It's finished.

275
00:25:46,966 --> 00:25:51,881
She reaches down with her forelegs
to check how far away she is from the ground.

276
00:25:54,686 --> 00:25:57,962
Then she snips most of the framework threads

277
00:25:58,046 --> 00:26:01,959
and holds the fuzzy rectangle
between her four front legs.

278
00:26:02,046 --> 00:26:03,638
She's ready.

279
00:26:06,806 --> 00:26:11,197
Her enormous eyes are so sensitive
she can hunt in near-darkness.

280
00:26:13,126 --> 00:26:15,321
A bush cricket would make a rich meal,

281
00:26:15,406 --> 00:26:18,842
but it's very powerful
and it could put up a good fight.

282
00:26:40,566 --> 00:26:42,841
Now it must be parcelled up

283
00:26:42,926 --> 00:26:45,724
and the fuzzy silk makes excellent wrapping,

284
00:26:45,806 --> 00:26:48,115
just as it does for Hyptiotes.

285
00:26:53,086 --> 00:26:56,203
In Australia, there's a species of spider

286
00:26:56,286 --> 00:26:59,676
that has taken web construction
a stage further still.

287
00:26:59,766 --> 00:27:03,076
It builds not just in two dimensions but three.

288
00:27:03,166 --> 00:27:08,160
It regularly takes up residence in
people's backyards and on their verandas.

289
00:27:08,246 --> 00:27:10,760
There's one under this plant holder.

290
00:27:10,846 --> 00:27:14,236
It's the notorious and very venomous redback.

291
00:27:15,326 --> 00:27:20,161
And what's brought it here
is the extraordinary way in which it uses silk.

292
00:27:21,766 --> 00:27:26,840
The female usually builds at night
and constructs this very elaborate web.

293
00:27:26,926 --> 00:27:29,315
Its not just wide, it's deep.

294
00:27:30,646 --> 00:27:34,639
To make it, she needs two flat surfaces,
one beneath the other,

295
00:27:34,726 --> 00:27:38,401
and that's what she's found
underneath the plant holder.

296
00:27:38,966 --> 00:27:42,322
First, she drops down, pulling a thread behind her.

297
00:27:44,966 --> 00:27:47,799
She sticks the end to the veranda floor.

298
00:27:52,166 --> 00:27:56,045
Then she goes back up again,
trailing a second line,

299
00:27:56,126 --> 00:27:59,402
which she sticks to the first, so strengthening it.

300
00:28:01,366 --> 00:28:03,641
Then she pulls the line tight.

301
00:28:03,726 --> 00:28:06,763
That is a crucial element in the construction.

302
00:28:15,206 --> 00:28:16,958
Down she goes again.

303
00:28:40,126 --> 00:28:41,798
By the time she's finished,

304
00:28:41,886 --> 00:28:46,596
she will have fixed several dozen
of these sticky, taut, vertical lines.

305
00:28:49,246 --> 00:28:51,806
An ant is approaching in the distance.

306
00:28:51,886 --> 00:28:54,684
An orb web would never catch one of these.

307
00:28:56,926 --> 00:28:59,963
It's a scout, leading an exploring party.

308
00:29:00,406 --> 00:29:02,158
Searching beneath the plant holder,

309
00:29:02,246 --> 00:29:06,080
it's almost bound to blunder
into one of the redback's lines.

310
00:29:08,926 --> 00:29:12,043
It struggles and so seals its fate.

311
00:29:14,926 --> 00:29:17,679
And its followers go the same way.

312
00:29:27,806 --> 00:29:32,163
The threads carry the vibrations
back to the redback waiting above.

313
00:29:33,606 --> 00:29:35,756
She has no need to hurry.

314
00:29:35,846 --> 00:29:39,441
Her meals are suspended in midair.
Escape is impossible.

315
00:29:39,846 --> 00:29:42,838
She hauls them up in her own good time.

316
00:29:50,926 --> 00:29:54,316
The redback's trap
is certainly economical with silk,

317
00:29:54,406 --> 00:29:58,877
but one North American spider
hunts with just a single filament.

318
00:30:00,166 --> 00:30:02,805
This may look like a bird dropping

319
00:30:02,886 --> 00:30:07,038
but that's just a disguise
to fool anything that might want to eat it.

320
00:30:07,126 --> 00:30:09,162
In fact, it's a spider

321
00:30:09,246 --> 00:30:13,080
and one with an even more
extraordinary hunting technique.

322
00:30:13,566 --> 00:30:15,443
It's a bolas spider.

323
00:30:16,086 --> 00:30:19,317
Throughout the day, she remains motionless,

324
00:30:19,406 --> 00:30:23,081
but when evening comes, she prepares for action.

325
00:30:28,766 --> 00:30:32,918
She abandons her disguise and starts to move.

326
00:30:37,126 --> 00:30:41,677
Slowly, she makes her way down
to the underside of the leaf.

327
00:30:46,126 --> 00:30:49,243
There she hangs from a horizontal thread.

328
00:30:53,286 --> 00:30:57,199
Next, she starts to spin a single strong line,

329
00:30:57,286 --> 00:31:00,642
pulling it out of her spinneret with her back legs.

330
00:31:08,286 --> 00:31:11,483
And at the end, there is a sticky globule.

331
00:31:13,086 --> 00:31:14,917
This is her bolas.

332
00:31:15,006 --> 00:31:16,883
It's all she needs.

333
00:31:16,966 --> 00:31:19,241
She climbs back up to her leaf

334
00:31:19,326 --> 00:31:22,477
and takes up her position on the horizontal thread,

335
00:31:22,566 --> 00:31:26,525
with her weighted filament
dangling from one of her front legs.

336
00:31:42,406 --> 00:31:43,475
A moth.

337
00:31:43,566 --> 00:31:46,399
She whirls her bolas but misses.

338
00:31:48,046 --> 00:31:51,004
But she has ways of enticing the moth back.

339
00:31:51,086 --> 00:31:54,044
She can produce a pheromone,
a chemical perfume,

340
00:31:54,126 --> 00:31:56,435
that the moth finds irresistible.

341
00:31:56,526 --> 00:31:58,517
What is more, she can change it

342
00:31:58,606 --> 00:32:02,599
to suit the particular species of moth
that happens to be around.

343
00:32:05,126 --> 00:32:07,082
The moth comes back.

344
00:32:11,606 --> 00:32:13,676
This time she's got it.

345
00:32:24,326 --> 00:32:26,794
Now, she starts to wrap it.

346
00:32:34,166 --> 00:32:36,282
But she's not finished yet.

347
00:32:41,366 --> 00:32:44,756
Different moths and a different pheromone.

348
00:32:54,646 --> 00:32:57,160
Silk can do other things as well.

349
00:32:57,646 --> 00:33:01,275
It can totally change a spider's lifestyle

350
00:33:01,366 --> 00:33:03,436
and turn a solitary killer

351
00:33:03,526 --> 00:33:06,563
into a creature that hunts in great packs.

352
00:33:06,646 --> 00:33:12,164
This enormous web above me
contains thousands of spiders.

353
00:33:12,246 --> 00:33:15,079
They're all tiny but because they work together,

354
00:33:15,166 --> 00:33:18,363
they can kill prey many times their own size.

355
00:33:21,046 --> 00:33:22,957
Any spider sitting on its web

356
00:33:23,046 --> 00:33:27,642
might be expected to react aggressively
towards another that approaches it,

357
00:33:27,766 --> 00:33:29,324
but not these.

358
00:33:33,806 --> 00:33:38,675
These tiny ant-size spiders
seem totally relaxed in one another's presence.

359
00:33:38,846 --> 00:33:41,599
More than that, they cooperate with one another,

360
00:33:41,686 --> 00:33:46,441
working together to repair and extend
their huge silken palace.

361
00:33:47,686 --> 00:33:50,519
There are tens of thousands of them in this one

362
00:33:50,606 --> 00:33:52,961
and they are constantly at work.

363
00:34:04,686 --> 00:34:09,885
Their home can rise
15, 20 metres up towards the canopy.

364
00:34:11,166 --> 00:34:15,284
It's so big, it's a major obstacle
in the airways of the forest.

365
00:34:18,606 --> 00:34:22,963
This cricket weighs several hundred times
as much as one of these spiders.

366
00:34:23,046 --> 00:34:25,844
However, the slightest attempt to free itself

367
00:34:25,926 --> 00:34:29,919
only serves to attract lots of them
from all over the giant web.

368
00:34:48,166 --> 00:34:50,919
Soon it's surrounded by hundreds.

369
00:34:52,046 --> 00:34:54,321
They squirt glue from their spinnerets,

370
00:34:54,406 --> 00:34:57,045
immobilising the cricket limb by limb.

371
00:35:07,846 --> 00:35:12,124
They sink their tiny jaws
into its most vulnerable places,

372
00:35:12,206 --> 00:35:14,879
its joints, and inject their venom.

373
00:35:35,926 --> 00:35:38,599
Before long, the cricket is dead

374
00:35:38,686 --> 00:35:42,315
and the horde of tiny victors share their vast meal.

375
00:35:58,486 --> 00:36:02,399
On occasion, even a solitary spider
must meet another spider.

376
00:36:02,486 --> 00:36:05,000
Male, after all, must meet female.

377
00:36:06,046 --> 00:36:09,482
This is a male Argiope
and he's looking for a mate.

378
00:36:12,606 --> 00:36:15,803
But she is huge, ten times bigger than he is.

379
00:36:15,886 --> 00:36:21,404
He has to be very careful if he's not to be
mistaken for prey and eaten.

380
00:36:28,206 --> 00:36:31,596
Once he reaches her, he starts stroking her body,

381
00:36:31,686 --> 00:36:33,563
nibbling her toes.

382
00:36:33,646 --> 00:36:37,321
From their taste,
he can tell whether the female is a virgin.

383
00:36:37,406 --> 00:36:40,443
If she is, she will be less likely to eat him.

384
00:36:43,566 --> 00:36:48,594
To confirm that her taste is encouraging,
he wipes his feet across his mouth.

385
00:36:50,806 --> 00:36:53,001
Apparently, he's reassured

386
00:36:53,086 --> 00:36:56,476
for he starts to snip
some of the strands of her web

387
00:36:56,566 --> 00:36:59,205
to create an open space in it.

388
00:37:02,766 --> 00:37:05,963
He runs a line across it, down towards her.

389
00:37:12,326 --> 00:37:15,762
And now, he plucks it like a guitar string.

390
00:37:26,246 --> 00:37:27,918
He's doing very well.

391
00:37:28,006 --> 00:37:30,201
She's not attacked him, yet.

392
00:37:40,486 --> 00:37:44,604
She spreads her eight legs.
It's a clear invitation to mate.

393
00:37:47,846 --> 00:37:52,397
He checks the taste on his legs again
and decides to go further.

394
00:37:54,446 --> 00:37:55,799
He pauses.

395
00:37:55,886 --> 00:38:00,277
After mating he has, at best,
a 50-50 chance of staying alive.

396
00:38:01,046 --> 00:38:03,879
But nothing ventured, nothing gained.

397
00:38:03,966 --> 00:38:06,639
He moves in and delivers his sperm.

398
00:38:10,566 --> 00:38:12,602
But his luck runs out.

399
00:38:12,686 --> 00:38:14,165
Virgin she may be

400
00:38:14,246 --> 00:38:18,876
but, with mating completed,
she grabs him and binds him in silk.

401
00:38:39,686 --> 00:38:41,756
She will eat him later.

402
00:38:45,846 --> 00:38:49,634
Some spiders don't spin webs of any kind,

403
00:38:49,726 --> 00:38:53,196
but they still need silk to help them find a mate.

404
00:38:53,486 --> 00:38:55,954
And there's one such just here.

405
00:38:56,726 --> 00:39:00,480
It's a female wolf spider.
A solitary, wandering hunter.

406
00:39:04,606 --> 00:39:09,555
Like all spiders, she trails a dragline
of silk behind her wherever she goes.

407
00:39:09,846 --> 00:39:12,235
It's a safety line in case she falls

408
00:39:12,326 --> 00:39:16,035
or is blown away
or needs to drop out of sight in a hurry.

409
00:39:16,806 --> 00:39:18,524
And here's a male.

410
00:39:24,046 --> 00:39:25,843
He's noticed her dragline.

411
00:39:25,926 --> 00:39:29,282
The taste of a silk line
is very informative for him, too.

412
00:39:29,366 --> 00:39:32,199
It tells him that it comes from a female,

413
00:39:32,286 --> 00:39:33,958
so he follows.

414
00:39:37,126 --> 00:39:41,563
His black palps are covered in hairs
which are extremely sensitive.

415
00:39:44,806 --> 00:39:49,721
Each hair contains a nerve
which can detect even minute quantities

416
00:39:49,806 --> 00:39:51,558
of female pheromone.

417
00:39:53,126 --> 00:39:55,594
Now, he's within sight of her.

418
00:39:55,686 --> 00:39:59,281
Being active hunters,
wolf spiders have excellent eyesight,

419
00:39:59,366 --> 00:40:03,723
so he uses his black palps
to send visual signals to her.

420
00:40:14,086 --> 00:40:16,554
This display is not slowed down.

421
00:40:16,646 --> 00:40:18,477
This is how he does it.

422
00:40:18,606 --> 00:40:21,484
It takes a lot of energy
and, while he's performing,

423
00:40:21,566 --> 00:40:23,557
his heartbeat triples.

424
00:40:40,286 --> 00:40:43,562
She encourages him by tapping her legs.

425
00:40:54,966 --> 00:40:57,560
He's now within striking distance.

426
00:40:57,646 --> 00:41:00,843
The palps he's waving,
like those of all male spiders,

427
00:41:00,926 --> 00:41:02,723
are loaded with sperm.

428
00:41:10,126 --> 00:41:13,482
He leans over,
inserts one of them into her abdomen,

429
00:41:13,566 --> 00:41:15,796
and pumps his sperm into her.

430
00:41:33,246 --> 00:41:35,919
Then he does the same with the other.

431
00:41:38,086 --> 00:41:41,999
And that's that, at any rate,
as far as he is concerned.

432
00:41:44,886 --> 00:41:49,243
Three weeks pass and the female's ovaries
start to produce eggs.

433
00:41:49,326 --> 00:41:53,444
The male's sperm that the female
has been holding within her for all this time

434
00:41:53,526 --> 00:41:55,960
is now released and fertilises them.

435
00:41:56,486 --> 00:41:58,716
At last, she's ready to lay.

436
00:42:00,366 --> 00:42:03,438
But she needs a safe place in which to do so.

437
00:42:05,366 --> 00:42:09,598
And, once again,
silk provides a solution to her problems.

438
00:42:10,886 --> 00:42:13,798
She starts by spinning a silken sheet,

439
00:42:13,886 --> 00:42:16,878
stretched between fragments of the leaf litter.

440
00:42:24,326 --> 00:42:28,444
She uses that fuzzy silk
that comes from multiple nozzles.

441
00:42:28,526 --> 00:42:31,916
It will provide a soft padding to protect her eggs.

442
00:42:51,966 --> 00:42:55,197
She expels a drop of liquid onto the sheet.

443
00:43:01,326 --> 00:43:05,558
And into the liquid, she injects her fertilised eggs.

444
00:43:28,806 --> 00:43:31,274
There may be several dozen of them.

445
00:43:32,126 --> 00:43:34,686
She checks that the drop has dried.

446
00:43:42,926 --> 00:43:46,043
She adds more fuzzy silk to protect it

447
00:43:46,126 --> 00:43:49,801
and its vulnerable contents
from knocks and bumps.

448
00:43:53,926 --> 00:43:55,996
Then she changes silk

449
00:43:56,086 --> 00:44:00,284
and starts to spin a tougher kind
to cover the whole capsule.

450
00:44:22,406 --> 00:44:25,637
She cuts the platform free from its attachments

451
00:44:25,726 --> 00:44:29,685
and goes round it,
pinching the cut edges firmly together.

452
00:44:40,886 --> 00:44:45,482
Finally, she covers the whole parcel
with a waterproof silken wrapping.

453
00:45:00,566 --> 00:45:05,003
She now carries her precious package with her
wherever she goes.

454
00:45:09,326 --> 00:45:11,794
She seeks out patches of sunlight

455
00:45:11,886 --> 00:45:16,084
so that she can warm it
and speed the development of the eggs within.

456
00:45:18,446 --> 00:45:21,882
It's a long process that may last several weeks.

457
00:45:28,006 --> 00:45:29,678
And then, at last,

458
00:45:29,766 --> 00:45:33,839
her babies are sufficiently developed
to leave their nursery.

459
00:45:56,006 --> 00:45:59,157
But, even now, she doesn't abandon them.

460
00:46:00,886 --> 00:46:03,719
They climb up her legs and onto her back.

461
00:46:04,646 --> 00:46:08,161
The egg capsule is now empty
and can be discarded.

462
00:46:12,486 --> 00:46:14,204
And away they go.

463
00:46:15,166 --> 00:46:20,001
It's a somewhat rough ride but the babies,
even at this early stage in their lives,

464
00:46:20,086 --> 00:46:22,998
know how silk can keep them out of trouble.

465
00:46:23,086 --> 00:46:26,476
They use it to tie themselves
to their mother's back.

466
00:46:36,646 --> 00:46:39,365
And then they use it for yet another purpose

467
00:46:39,446 --> 00:46:41,755
and produce it in such abundance

468
00:46:41,846 --> 00:46:47,045
that, in some seasons of the year,
it covers great areas of the open countryside.

469
00:46:55,326 --> 00:47:00,002
This wonderful shimmering carpet of gossamer,

470
00:47:00,086 --> 00:47:02,839
strands of the finest silk,

471
00:47:02,926 --> 00:47:06,362
is the creation of a million baby spiders.

472
00:47:06,806 --> 00:47:08,683
It's autumn in England

473
00:47:08,766 --> 00:47:12,076
and time for spiderlings to leave their mothers.

474
00:47:17,446 --> 00:47:20,438
The youngsters climb up the threads they've spun

475
00:47:20,526 --> 00:47:23,279
to reach the topmost twigs of the bushes.

476
00:47:26,886 --> 00:47:29,195
They tip their abdomens into the air

477
00:47:29,286 --> 00:47:33,996
and the gentle breeze catches the filaments
as they issue from the spinnerets.

478
00:47:37,246 --> 00:47:41,080
Some filaments drift down
and become entangled in the bushes.

479
00:47:54,086 --> 00:47:59,001
But when conditions are right,
the threads rise vertically upwards.

480
00:48:04,446 --> 00:48:06,596
And away the spiderlings go.

481
00:48:20,006 --> 00:48:24,079
On a calm day, they may only travel a few metres,

482
00:48:24,166 --> 00:48:30,196
but if there's a breeze, as there is now,
they can be swept up high into the sky.

483
00:48:30,966 --> 00:48:33,685
Spiderlings have been recorded

484
00:48:33,766 --> 00:48:38,715
thousands of feet up
and can travel for hundreds of miles.

485
00:48:43,406 --> 00:48:46,842
So silk can be used for transport

486
00:48:46,926 --> 00:48:50,441
as well as looking after the young, courtship

487
00:48:50,526 --> 00:48:52,915
and, of course, catching prey.

488
00:48:53,006 --> 00:48:55,474
In an area of heath like this around me,

489
00:48:55,566 --> 00:49:00,560
it's been estimated that there's probably
14,000 miles of silk,

490
00:49:00,646 --> 00:49:04,036
enough to stretch from here
in England to Australia.

491
00:49:04,646 --> 00:49:06,238
Ingenious though we are,

492
00:49:06,326 --> 00:49:09,477
we've not yet been able
to invent anything as strong,

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as light or as elastic as silk.