You might fear spiders for their powerful venom,
their sharp fangs, and the creepy way that they scurry behind your furniture. But you can't deny
their talent for building amazing structures. Bridges are made of steel and
requires engineers. But the spiders do it win a way that man can't comprehend. From building their own fly traps, to knitting
their silken transformation chambers, to creating hot air balloons out of thin thread...:
We're entering the age of silk! Hi, I’m Danielle Dufault, and you’re
watching Animalogic: Second Nature. The history and evolution of silk can be a complex web of misconceptions. So let’s try to
untangle it. Let’s start with spiders. There are an estimated 100,000 species
of spiders throughout the world, each possessing a number of engineering skills
that qualifies him as a master craftsman. Up to 1000 times thinner
than a strand of human hair, spider silk is pound for pound five times
stronger than steel and tougher than Kevlar. Yet, if a single strand were stretched around the
entire Earth it would weigh less than 500 grams.
One of the few things lighter
than spider silk is Opera, which is the browser we used while
writing and researching this episode. Opera is really awesome. I like it
for doing research because it lets you organize and group your tabs into tab islands. I feel that if you have too many tabs
open it gets overwhelming. But having the option to separate them however
you like, makes it easier. For example, here’s all my tabs about batfish
separate from all my other stuff. And when I’m reading and need some quick
answers, I love using a feature called Aria, which is an AI chat connected directly with
the browser that gives you answers immediately. I got curious and used it to see if it would
be possible to make a dress out of spider silk, and it seems in theory it
is! How cool would that be? You can also highlight words to get quick
definitions and explore subjects further. Opera also has an inbuilt ad blocker and a
vpn. You don’t need extra extensions to work. These two features help you have a private
and comfortable experience. Pages load faster, it hides your location for private browsing,
and it’s completely free and unlimited. And if you’re not working
and just want to have fun, there’s a lot of insanely smart
features that make everything easier. There’s a customizable sidebar for your
music player and social media accounts, so you can have all your social
media accounts connected and listen to music without having to go to their websites. And also, when you’re watching videos,
you can make them pop with lucid mode, which sharpens them. See the difference? I really love Opera and I’m sure you
will too. Click on the link in the description to see how much better
your browsing experience can be. And now back to the amazing animals who
make sticky thread to control their world. Not all webs stick the same. Some webs
stick to insects with droplets of glue. Other webbing cling to the insect’s hair and
legs like cotton threads of a shirt to a bur. But still, there are more than 40 000
different spider species on the planet and each has a web suited for its usage.
So there’s a lot of variety out there. Some spiders will station themselves in the center
of the web. Other, however, keep hidden nearby. When the trap is sprung, the vibrations of
the insect struggle are carried to the spider, which immediately rushes out to subdue its
prey, and then wraps it up for later meal. It’s estimated that spiders eat between 400-800
million metric tons of insects every year. For comparison, the entire human
population consumes approximately 400 tons of meat and fish during the same time. That’s a whole lot of web catching going on! While waiting for some juicy marvel to
blunder into its trap, some spiders will station themselves in the center of the
web. Others, however, keep hidden nearby when the traffic from the vibrations of the
insect struggles are carried to the spider, which immediately rushes out to subdue its prey
and carefully packaged up for a future meal. Speaking of which, there are
5 basic types of spider webs. Sheet webs. You’ve probably seen these if you go for a
hike in the woods or across a field or marsh. Most commonly associated with members of
the Linyphidae family - like the Platform Spider - sheet webs are flat sheets of silk
spun between blades of grass or branches. The spider spins a net of webbing above the sheet. When flies hit the net they bounce onto the
sheet webbing and are caught in the trap. Another type of web is Tangle Webs
or Cobwebs – not to be confused with the dusty webs that collect
in the corners of your room. These are made by many spiders of the Theridiidae
family – like the house spider and the notorious black widow. Tangle webs are a messy,
disorganized jumble of threads that are laced with sticky droplets. When an insect
crawls across a thread it breaks drawing the unsuspecting victim up into the centre of the
tangle where it becomes hopelessly entangled. Then we have the Triangle and the Funnel webs. The first is a triangular web where the spider
releases a coil of silk that entangles its prey. And the second is a funnel shaped structure
of silk. The spider hides in the small end of the funnel and waits for prey
insects to stumble into their doom. And last, the web we all know and
love, the popular and ever-romanticized Spiral Orb Web. There are close to three
thousand species of orb weaver spiders. There are close to three thousand
species of orb weaver spiders. Their webs are typically found outside and are
the most common and popular type of spider web. And who can blame them? They are so
impeccably designed with superior … taste. No matter the species, spiders
are highly skilled engineers. They create amazingly complex webs
using a gland called a spinneret. May not need all of it. She manufactures her rope from silk glands in her
body as she goes along. The spin array located at the tip of her abdomen, release five different
kinds of liquid from 3600 whole. She can spin a single strand, a heavy cable or a broad band under her careful control. The
silk may be elastic or non elastic, sticky or sticky colored or transparent from it.
The spinneret is located at the bottom of it’s abdomen and allows the spider to produce a
variety of silk used for different purposes like for webbing, creating drop lines,
cocooning prey, protecting eggs and flying. Wait…what?!? Yes. Spiders can fly. Sort
of. This peculiar arachnid pastime is actually called ballooning. And it’s another
amazing thing that its silk is used for. Spiders go ballooning by climbing to a
high up open area. They raise their two front legs up to check the wind speed and
possibly direction. And then they raise their abdomens skyward releasing
threads of webbing into the air, kind of like a parachute. When a
breeze comes along they float away. Seems pretty simple right? Well, the process is a
lot more complex than it looks. Ballooning spiders are actually utilizing electrostatic repulsion by
using the Earth’s electric field to take flight. When they release their silk the threading
becomes negatively charged and repels against the negatively charged surface they’re sitting
on. This makes the spider balloon upwards. Scientists believe that spiders have evolved
to go ballooning for a variety of reasons, like escaping predators or finding new sources of food. Or hey, maybe just for a blast! I mean, why
not? Spiders just want to have fun too, right? But their fun-loving ways were
not always the case. The early ancestors of spiders couldn’t even spin webs! It was only recently that scientists
finally found the spider’s missing link: its long extinct, silk producing -
but not web spinning - ancestors, collectively known as proto spiders. The most
famous of these is attercopus fimbriungus. It lived around 400 million years ago,
a time before the first tree ever lived! They weren't really spiders yet. A
protospider like chimerarachne yingi had a tail and it wasn’t able to spin
webs like a spider that uses spinnerets. By this point flying insects hadn’t
evolved so there was no need for a proto-spider like Attercopus
Fimbriungus to go to higher ground and spin webs in taller plants because
there wasn’t anything flying up there. All the prey was on the ground. So that’s why
its webbing was on the ground as well. The silk was also used to line their nests,
create homing trails and protect egg sacs. Evolution doesn’t work in a
vacuum. Everything works together! And once insects took flight we believed
that Attercopus Fimbriungus evolved. It’s spigots - that were not very precise -
adapted to spinnerets and then they were up in trees spinning intricate webs. And
that’s how the modern spider was born. But as new species appear, some evolve
completely new hunting techniques, while others stay closer to
their ancestors’ behaviour. For instance, as mentioned previously, funnel
spiders spread blankets of webbing across the grass and other vegetation … just like
Attercopus Fimbriungus. This has led scientists to think that sheet webs are the
type of web that’s ancestral for all spiders. The questions that surround evolution and the development of specific tools and traits
in arachnids are fascinating and complex. But one of the more recent and awesome instances
of arachnid evolution occurred not that long ago. Decoy spiders are learning to use debris
and the carcasses of their prey to create dummy versions of themselves. Some of these
decoys even have the right number of legs! Apart from the spooky idea that spiders may
be able to count, the most amazing thing was … That decoy spiders all over the world are
learning to do the same thing independently, with one sighting in Peru and
another 12000 miles away in the Philippines. An amazing
case of convergent evolution. But some of the most interesting spider
adaptations are happening closer to home, right in our cities, because of Human
Induced Rapid Environmental Change. Researchers are discovering that cities are actually making spiders grow
bigger and multiply faster. Well say Cincinnati, or Minneapolis, or New
Orleans. A city of half a million inhabitants. Spiders removed from inner city
parks weighed three times as much as those taken from bush land areas.
They also discovered that the city spider’s ovaries were significantly
bigger than those from rural areas. This adaptation is likely due to an increase of
temperature and food availability in the city. And boy, are spiders ever changing their food habits!
And part of it has to do with getting over their fears! Spiders are historically photophobic, meaning
that they have an extreme sensitivity to light. That’s why they like hanging out in dark,
creepy places … like your basement. But researchers have recently discovered that city
spiders are rapidly losing their photophobia. City spiders are building webs around
streetlights to catch more prey at night, and more than their rural counterparts. Which
is totally changing the food chain game. But we expect no less from such an amazingly
adaptive ambush predator as the spider. An adaptation as helpful as silk is bound to
convergently evolve in several species. Other than arachnids, insects are the animals
most commonly associated with silk. Silkworms are the larvae of the moth bombyx mori, which is a domesticated
version of the wild silkmoth. Larvae produce silk to build their cocoons,
where they metamorphose into moths. 5000 years ago they were domesticated
in China. The artificially selected new species requires human help to survive,
but it can also make a lot of silk. Domesticated silkworms eat more, grow
faster, get larger, and build bigger cocoons. A single silkworm can make a thread
300 to 900 m long to build its cocoon, but the thread is so fine that you need
over 2000 cocoons to make a pound of silk. Over 10 billion cocoons are harvested
worldwide each year to make shiny clothes. More than 4,000 years ago, so the legend claims, Chinese hand acquired the skill to weaving
the silk and thread, thus building with the silk of cocoons of silkworms that feed on the
tender leaves of mulberry trees of the valley. But though these moths are the most
prodigious silk cocoon builders, there are hundreds of insect species to do the
same, in various degrees of sophistication. Raspy crickets make shelters
with silk very similar to that of silkworms. But they evolved
this adaptation independently. Similarly, bull ants, webspinners, silverfish, flies, and many moths and butterflies use silk to
protect themselves when at their most vulnerable. Honey Bees even have silk glands in their
mouth that they use when building their wax cells to pupate. This silk is tougher
and stretchier than silkworm silk and it’s being studied for usage in the medical field. The webspinner is the closest
silk-producing animal to spiderman. Their silk glands are located in their
forelimbs and they shoot it into walls… but in their case it’s not for catching
bad guys but for building homes. Yep, this strange little guy lives in
large homes draped in silk. Luxurious. They would be runners-up for the award for best silk-based engineering. The gold
goes to the amazing weaver ant. Weaver ants build their colonies in the tree
canopy, attaching tree leaves to each other to build protective chambers. Their name comes
from the way they glue the leaves together. Their larvae naturally make silk to make
a cocoon, but since they’re already safe enough in the colony, the adults use their
sticky silk as their version of concrete . Worker ants carry the larvae to the
construction site and use them as glue guns. The larvae are held in the worker's
mandibles and are softly squeezed while the worker moves back and forth from
one leaf to another. They’ll continue with the process with several leaves until a ball
of leaves as big as a volleyball is created. But that’s not all, in the ocean, pinna
nobilis are the main producers of sea silk. They’re mussels up to 60 cm tall that
secrete silk to attach themselves to rocks or the seabed. The silk is strong
enough to be used to make cloth, even though each individual
strand is only about 6 cm long. This mat of strands is known as a byssus, and
is common in several species of pen shells, true mussels, and freshwater mussels. Silk is for sure more of an invertebrate
animal feature but there are a couple of vertebrate species that are learning
from our invertebrate friends. Carp have sticky silk that they
use to hold their eggs together and glue them to the rocks or
plants. Many fish species have similar behaviours and lay their eggs in
sticky rafts, so this isn’t that unusual. Spider Goat! It lives, it breathes, and
it’s here to shoot silk out of its udders. They’re genetically modified goats that have an orb-weaver spider gene in
the milk-producing area of their DNA. Their milk is full of silk proteins, and
it can then be processed to extract all the silk. This is an emerging area of
research, but if successful it can be a much more efficient way to get strong silk to
repair ligaments and other medicinal purposes. There is silk all over the animal world
and its convergent evolution sheds light on the evolution of animal shelter-building,
trap-making, and tool use. And now that we’re learning how it works, we can harness
the power of silk to benefit humanity. What mysteries of evolution do you want me to
talk about next week? Please let me know in the comments, and be sure to subscribe for
new episodes of Second Nature every week. Thanks for watching!
