MALE SPEAKER: Let me just
introduce our speaker today.
So we have Leslie Brunetta
who's an independent writer here
in Cambridge, who
has collaborated
with an evolutionary biologist
to understand spider silk.
And the reason she's
interested in spider silk
is not because she's
a crazy spider lady--
LESLIE BRUNETTA: But now I am.
MALE SPEAKER: But now she is.
But because spiders
turned out to be
a great way of understanding
the process of evolution
and natural selection.
So Leslie--
LESLIE BRUNETTA: I can hold
up the book and show it.
MALE SPEAKER: Why
don't you tell us
how you got
interested in spiders?
LESLIE BRUNETTA: How I
got interested in spiders.
I'm an English major.
I have a Master's in English.
I have nothing past
high school science,
which puts me at a big
disadvantage in this room,
I suspect.
And what I was working for-- I
have written science articles
for various alumni
magazines, Tech Review,
and I wrote a kind
of joke commentary
on evolution-- human
evolution-- for NPR.
And I had had a couple of
NPR commentaries before,
and they said they would
take this commentary.
It was all about how
you, unfortunately,
can't throw four-year-old
kids into the pool,
and they just swim like dogs.
Whereas that's true about
apes, but not about monkeys.
So that's all interesting.
So they told me that they
would take the commentary
if I got it vetted by an
evolutionary scientist.
And I'm a freelancer.
So I, of course, said, oh, yes.
I will do that.
And then it was like,
hang up the phone.
It was like, ahh!
I don't know any
evolutionary scientists.
How am I going to do this?
My husband at the time worked
at the late, lamented Arthur D.
Little.
And he worked with
somebody there.
We had gone to branch with them.
And he said, what
about Bob's wife?
I think she's an
evolutionary scientist.
So I called Bob's
wife, Kay, who--
Kay Craig, who's the
co-author Catherine L. Craig.
Turns out that she did some
really pioneering research
on the evolution of spider silk.
And she was nearly
finished with her monograph
and she just needed it
smoothed out a little bit.
So I said that I
would-- I have a copy
of her monograph over there,
if you want to see it.
So I was copy editing
her book, and they
were parts of it I
didn't understand.
But what I suddenly realized
was that although I thought
I understood
evolution-- I mean, I
had been reading the
"Science Times" every Tuesday
since it started
publishing and all of that.
Although I thought I
understood evolution
and natural
selection, I realized
that I have these very,
very common misconceptions
about evolution and
natural selection.
This was right at the time when
the whole intelligent design
thing was really bubbling up.
And I realized,
reading her book,
that you could use spiders and
the evolution of spider silk
to explain the
process of evolution
and the process of
natural selection
to non-biologists in a way
that would be extremely
difficult to do with any
other kind of organism.
And, I mean, I'll
explain what-- so this
will end up being a
little bit repetitive--
but it's because the silks
themselves are proteins.
And since the 1990s, they've
done genetic-- the genes
behind some of these proteins.
There's still a lot to go.
But it's very hard to
figure out the genetic basis
and the genetic evolution of,
let's say, bird flight, right?
Because it's very,
very complicated.
But what I'll show you
when we get this going
is that there's a sequential
evolution of spider silks.
Silks that they still use now.
And those can be examined
and characterized,
and so you can actually see
the genetic changes that
lead to functional changes
that then lead to an increased
chance of survival.
So it turned out
that-- I thought
it wouldn't take me-- take us--
very long to write this book.
It ended up taking a lot
longer than I thought
it would, because I had
the hubris of most writers,
which is I didn't know
what I didn't know.
So I had to kind
of school myself
in evolutionary theory and
proteomics and genetics.
But anyway, it just turns out
that spiders are this fantastic
vehicle for explaining
evolution to non-biologists.
So that's the long story
of how I got into this.
So this kind of web, this is
properly known as an orb web.
And I would risk saying
that when most people think
of a spider web, this is
the kind of spider web
that they think of.
This one has been
dusted with cornstarch.
So usually when you see spider
webs that you could really
see like this,
they've usually been
dusted with some kind of powder
so they can be photographed.
So to build an orb
web, a spider spins
a number of different
kinds of silk.
So there's one
kind of silk that's
in the frame lines
and the radial lines.
Then they use a silk--
a different kind
of silk-- to build a scaffold
to help them build it.
Then they eat that
while they lay down
a different kind of silk, which
is this, the capture spiral.
And then there are different
kinds of silk proteins
that are used, for instance,
to anchor the lines, to anchor
the lines to each other.
And there's also a glue--
protein silk glue--
that coats the capture line.
And each of these
silks is produced
in a different silk
gland in the spider.
So pretty clearly, this is
an amazing construction.
And as I've said
before, the book
itself is about two things.
One is the story of the
evolution of spider silk,
and-- I'm sorry over
there-- and the other one
is an explanation of what
natural selection really is
and how it really works.
Most people who are not
evolutionary biologists
have a lot of
misconceptions about that.
And it turns out that
spiders and their silks
offer an unusually
good view of this
because the silks are
proteins and the proteins--
all proteins are
dictated by genes.
And with today's
research techniques,
you can see how a
change in a silk gene
may lead to a change in
silk protein structure.
And we can then see
how the environment may
favor one protein
structure over another.
So for instance, you can
have a change in a silk gene
that may result in a silk
protein becoming stronger
or stretchier or stickier.
And the other thing
is that now we
are finding more and more not
just how different spiders
are related to each other--
there are over 40,000 known
species of spider.
We can not only see how
the species are related
to each other, we can now see
how the silk genes and the silk
proteins are related
to each other
and descend from earlier
genes and proteins.
So what I'm going
to show you today,
I'm not going to go into the
deep gene and protein stuff.
But we do go into
it in the book.
But I'm going to show you
some of the astounding
variety in the ways that
spider silks and silk
uses have evolved.
So that orb web is
pretty spectacular,
but that's really--
that's the least of it.
When spiders' ancestors
were evolving--
they began evolving about
380 to 400 million years ago.
Back then, plants-- tallest
plants were about this tall.
There were no birds.
There were no mammals.
There were no reptiles around.
But there were plenty of
very predatory arthropods.
So arthropods you probably
know are spiders, insects,
crustaceans, the things with
jointed legs and exoskeletons.
So if you were
producing silk back
then, what you might
want the silk for
is something like this.
These are a type of
spider called mesophiles.
There are three surviving
major lineages of spiders.
These belong to the
oldest surviving lineage.
They live only in
Southeast Asia.
They're pretty hard to find
and pretty hard to study.
You can see, very interesting
thing about them is that they
have this segmented abdomen,
which other spiders don't.
And that shows you
their ancestry.
And look how it's using silk.
It has a burrow underground.
So it hides out from its
predators in the burrow.
It lines the burrow with silk,
which helps hold the walls up.
It also helps mediate humidity.
It uses silk to knit
together debris and create
this flap-like trap door.
So most of the time, it
will be hiding in there
and will actually be
holding the door shut.
So that defends it
against its predators.
Then this particular
kind of species--
and a bunch of other ones--
set out these silk trip lines.
And these are nocturnal,
which also makes sense,
if you think of plants only
being this tall, because there
was very little shade.
What they do is they hang out
on the edge of the burrow.
They array their legs
along the trip lines.
And then when anything walks
by and they feel the vibration,
they lunge out, grab the
prey with their fangs,
and drag it back into the burrow
and close the flap and eat it.
So there are about 90 species--
90 known species-- of these.
As far as they're concerned,
insects never evolved flight.
They're just fine
in their burrows.
So the second major
lineage of spiders
is known as the mygalomorphs.
The mygalomorphs include the
tarantulas and their closer
relatives.
The oldest known--
oh, I should have
said that this is very similar.
These are like the coelacanths
of the spider world.
They are very similar
to fossil mesophiles
from 290 million years ago.
The oldest mygalomorph fossil
is about 240 million years old.
By then-- do you have a-- yep?
AUDIENCE: Yeah.
I was wondering
whether, as you go
through all the
various species--
I assume there's going to
be [INAUDIBLE] or something.
I'd just be curious to know
what proportion of them
are actually poisonous.
Like, are any of
these poisonous?
LESLIE BRUNETTA:
Well, it depends
on what you mean by poisonous.
They're all venomous.
So if you mean
sort of medically--
I think they call it medically
interesting or medically
significant, very,
very few spiders
are medically significant.
And it seems like the bulk
of those are in Australia.
Black widows are
medically significant.
Recluses-- however, it turns
out that most reported recluse
bites are actually
MRSA infections and not
spider bites.
Spiders very, very
rarely bite people.
Most things that are
reported as spider bites
are not spider bites.
AUDIENCE: OK, but
you're saying that all
use some chemical to
paralyze or kill their pray.
LESLIE BRUNETTA: Exactly.
For a long time, it was thought
that these didn't have venom.
And so it was thought that
venom system evolved later.
But this is one of
these things where
the better instrumentation
you get changes knowledge.
With much better, I think,
electron microscopes
or some kind of
imaging, just last year,
they discovered venom pores
in the fangs of these.
So anyway, by the time that
the mygalomorphs evolved
about 240 million years ago--
they evolved before that,
but that's the oldest fossil--
there were tall plants.
There were climbing
and flying insects,
and there were also
increasing numbers
of amphibians and reptiles.
And so in some of
the oldest surviving
branches of the mygalomorphs,
we see silk use like this.
This is called a collar web.
These are also nocturnal.
So there's a silk-lined
burrow under the ground.
They build it up about an inch.
They build a silk up,
knit debris into it.
And during the
day, it's flexible.
During the day
they close it shut.
And then at night,
they open it up
and hang out here
and wait to feel
the vibration of their prey.
So that's a collar web.
This is a turret web.
Similar, very similar idea,
but maybe two inches tall.
Again, you see the
debris knit into it.
So this-- mostly, it's
defense from predators.
But actually, you have to--
I've become a bit adept
at thinking at spider scale.
You have to start seeing
the world at spider scale.
That's only about
two inches tall,
but compared to being
underground in a burrow,
that really increases
your sensory field
when what you're
sensing is vibration.
And so this takes
advantage of insects
who have an instinct to climb.
And also occasionally flying
insects will land on the debris
and they'll come out.
AUDIENCE: How numerous are
constructions like this?
Like if you walk
through the woods,
will you see dozens
and dozens of these?
LESLIE BRUNETTA:
Well, it depends.
Well, if you really went
looking for them-- these kinds
of spiders,
mygalomorphs in general,
will tend-- and mesophiles,
actually, if you find one,
you'll find more.
Because they don't go far.
They can't disperse,
which I'll get to,
but they can't
disperse very far.
How common are they?
Not tremendously
common, but not uncommon
if you're in the right place.
So actually, these, which
are purse web spiders,
apparently if you know
where to look on Cape Cod--
I've never seen one, but if you
know where to look in Cape Cod,
you can find these.
You can get the scale of
this from this oak leaf here.
So this is a sapling.
And here is the purse web.
So it's essentially
a closed silk tube.
There's a silk-lined
underground burrow.
And then what the spider does
is hang out in this tube.
It's very sensitive
to any vibration.
So for instance, if
a beetle crawls up
here or a fly lands
on here, the spider
will rush to that
space-- this is
kind of like parchment
texture-- plunge
its fangs through,
grab the prey,
bring it inside, rush down
into the burrow for safety.
And then later it'll come back
and knit this back together.
So what you can see is
this looks like things
are progressing, right?
You now have taller
trees and flying insects,
and the mygalomorphs
are clearly starting
to use silk to reach upward.
But what you find out is
that's not how evolution works.
It's not going in any
particular direction.
Yes?
AUDIENCE: How long are those?
LESLIE BRUNETTA: They would
be about maybe six inches.
This is a more recently
evolved mygalomorph species.
And you see that it's
gone back to the burrow
with the trapdoor.
You see the silk lining.
You see the silk door.
And then there are
other mygalomorphs
who make burrows with no doors.
There are some who
make funnel webs,
which are kind of sheets of
silk with a little funnel-shaped
retreat.
There are some that
make these sort
of disorganized but
lacy-looking sheets.
And some of these sheet webs
can-- they're not adhesive.
They can slow
down-- it'd be kind
of like walking on
a slack trampoline.
So they slow down prey.
Some can entangle prey, but
they're not actually adhesive.
Yes?
AUDIENCE: So several of these
have moving parts, right?
And you said there's one
that tore through parchment,
and it would just
catch stuff afterwards.
The rest of them,
do any of them seem
to be the silk is so complicated
use a mechanical kind of thing,
or just the spider pushes
the door out of the way?
LESLIE BRUNETTA: Yeah.
Later evolution, there are
some mechanical things.
Yes.
That, and there's a
lot more than that.
But what now?
Let's see.
So what-- oh, I know.
So what I was going to say is,
you know the very common thing
of a spider dropping
on a thread?
None of these spiders that we've
looked at so far can do that.
Because none of them can
produce major ampullate silk.
And major ampullate silk
is that drag line silk.
Still, even though none
of them can do that,
there are 90 known
species of the mesophiles.
There are over three
thousand known species
of these various mygalomorphs.
So evolving at
around the same time,
but in a different
direction, are the bunch
of spiders known as--
the lineage of spiders
known as the araneomorphs.
They can all make this silk
that I'm talking about,
which is called
major ampullate silk.
This is the silk that
you hear about when
you hear about spider silk
being stronger than steel.
That's this kind of spider silk.
None of this kind of silk
is stronger than steel.
So major ampullate silk,
that's what they hang on.
That's what allowed spiders to
move out into the air space.
So, for instance, this is
known as a lamp shade web.
This is made by one of
the earliest evolved
but still surviving
araneomorphs.
And what you see
here-- so this again
has been dusted, so it
looks a little bit strange.
So what you can't see is
back inside the lamp shade,
there is a silk mat
that's laid down first.
Then the spider spins.
So arachnologists have
their own use of words.
Spinning means that the
spider uses its legs
to pull the silk
out of its body.
The mesophiles and
the mygalomorphs
will glue down the silk
and then walk away from it.
The araneomorphs pull the
silk out with their legs.
So technically, that's spinning.
So it will spin these lines--
these major ampullate lines.
Because of the tensile
strength of the lines,
you can see that this,
compared to anything
you've seen previously,
has a lot more space
between the lines.
And then they guide out
the shape in this way.
You can't see it,
and I'll explain why,
but there is an opposing
cone of lines this way.
But what do you really see here?
What you really
see is the spider
is doing what the earlier
evolved spiders did.
This is essentially
a burrow that's
been brought out underground.
The spider hides out inside
that from its predators.
The lines deter its predators.
But the biggest
advantage, and probably
the reason leading to the
evolution of major ampullate
silk, is that if things get
too hairy with the predator,
they can dive out on
their safety line.
So it allows you to--
oh, now, the powder
here is adhering to another
araneomorph innovation called
cribellate silk.
So the araneomorph
spiders will lay down
the major ampullate catching
lines, and at the same time,
they have a spinning
organ called
a cribellum that emits
tiny fibrils of silk.
They are so fine that it
takes about 4,000 of them
to equal a human hair.
And as they're laying
it down on this line,
they use a special comb of
hairs on their back legs
to kind of tease it back like
a Jackie Kennedy bouffant,
like this.
And you end up with
these waves of silk
that are so fine that
you get van der Waals
forces between the
silk and the molecules
and the exoskeleton
of their prey.
So that's all pretty innovative.
And you can see where
that allows spiders
to go to-- they've created this
completely new niche, right?
So major ampullate
silk, it allows
you to drop out of harm's way.
That's probably its
biggest benefit.
But it also opened
up new opportunities,
which is that it allows
you to hang silk-- sorry--
hang silk across wider gaps.
And it's very
strong, so it allows
you to hang heavy webs
across those gaps.
But the other thing it
allows you to do is--
you'll know this if you
read "Charlotte's Web"--
it also allows you to fly,
if you're an araneomorph
spiderling.
The problem with
being a spiderling
is that your siblings
and you are cannibals.
So you want to
disperse fairly early.
And araneomorphs
spiderlings disperse--
I told you the
arachnologists have
a lot of these technical terms.
The technical term for
what this spider is doing
is called tiptoeing.
It'll find a high point,
go on the tips of its legs,
and then put its hind
end up into the air
and start releasing
major ampullate silk.
And it can actually
sense air currents
on the bristles on its body.
And eventually, under
the right conditions,
they'll get enough lift from the
silk that they'll be lifted up.
Some of them will
just fail, and they'll
go just a couple of feet.
And who knows what
will happen to them.
But there are documented--
many, many documented-- cases
of lots of them being
whisked way up into the air
and going kilometers.
You probably know about
the explosion on Krakatoa.
One of the first people
to go back to Krakatoa,
the place was just
baked sterile.
But there was a spider there.
And that's how-- I mean,
I'm sure it didn't survive,
but this is how the
spider got there.
So by now, maybe,
you're thinking, OK.
They're making this silk.
They're stringing up these webs.
So probably we get
to the vertical orb
web, which I showed you first.
But that's not true.
Because orb webs
include that spiral
capture silk that I showed you.
Most araneomorphs, the
majority of araneomorphs,
cannot make that
capture spiral silk.
So instead, they're
making webs like this,
which is just a sort of
radiating web out of a crevice.
Funnel web, again,
coming out, usually,
of a crevice of some sort.
Suspended sheet webs.
And these are called ray webs.
And anywhere that you see
the powder sticking to them,
that's where there's
that cribellate silk.
The other lines are
not catching silks.
And they're also making
silk constructions
like this, which
we, unfortunately,
don't have these.
This is the European
water spider.
They live in ponds.
And that's just
sort of pond weed.
And so what they do is they
dive down from the surface.
They construct a major
ampullate silk sheet.
Then the silvery stuff
on the spider's body,
those are air bubbles adhering
to the bristles on their body.
So when they go
up to the surface,
the air sticks to them.
Then they swim down, and
then they brush the air off
under the sheet.
And then the air
collects up in the sheet.
And they keep doing
that until they produce,
essentially, a diving bell.
And the female will actually
lay her eggs in there,
and the spiderlings
will hatch out
in there dry and then swim out.
Yeah.
But then at the
same time, you've
also got thousands of species--
thousands and thousands
of species of araneomorphs that
just don't make any web at all.
And they've instead-- they've
gone back to trap door burrows,
like the wolf spiders, if you're
familiar with wolf spiders.
They are araneomorphs,
but they live in burrows.
The Huntsman spiders,
which run around.
Or in fact, the most
diverse spider family of all
are the jumping spiders.
There are about 5,000 known
species of jumping spiders.
If you look very-- it's
hard to see on this,
but if you look
very carefully, you
can see the safety line
coming from the back
of-- the major ampullate
safety line coming
from the back of the spider.
They don't always
hit their target.
Probably most the time,
they don't hit their target,
but they're saved by their
major ampullate line.
They can also use the
major ampullate line
to kind of control
their direction
as they come close
to their target.
So all of these
ways of negotiating
with the environment
are in different ways
enabled by major ampullate silk.
So not finally, which I'll
get to, you have the orb web.
But all the evidence
that we have so far
is that orb webs,
which we usually
think of as being
vertical, first
evolved as horizontal
structures.
So you're actually
looking down on this.
What I've found since
doing this book,
it really changes your habits.
I now have noticed that next
to a lot of utility poles,
for some reason there's
like an empty steel pole.
A lot of times if
you look in those,
you'll see a horizontal orb web.
And what they're
doing is they're
taking advantage of
insects hatching out
in there and their
instinct to fly up.
Yes?
AUDIENCE: What's the evidence
that the horizontal one evolved
first?
Like, I can't see how the
fossil record would show that.
LESLIE BRUNETTA: You can't
tell by the fossil record,
but because there are so many
living species of spider,
you can do all this sort
of taxonomy on them.
Yeah.
AUDIENCE: So it's a
phylogenetic tree?
LESLIE BRUNETTA: Exactly.
Exactly.
So but what's different about
this from a vertical orb
web is the catching
spiral is a different silk
protein from the
vertical orb webs.
And what you see here,
the adhesive on it,
is-- not adhesive,
its van der Waals
force-- it's the cribellate
silk, not the sticky glue
that we see on the
vertical orb webs.
It seems there's a
little bit of an evidence
shift at the moment.
It's very clear that
these evolved first.
We thought that--
we think, and most
of the evidence at the moment
says that the vertical orb
webs and the horizontal orb
webs have a very recent--
that's their most
recent common ancestor.
It may turn out that these
are slightly cousins, that it
evolved first, but there
was a shift and somebody
is actually-- there's some
postulation that this structure
may have evolved
and then disappeared
and then re-evolved, which,
for instance, happens
with the burrows.
So I'll be really interested
to see what happens with that.
So we get to the
vertical orb web.
So this is a piece of
capture spiral line.
Yes?
AUDIENCE: For the
horizontal webs.
Would humans find those sticky?
Or because it's only
van der Waals forces,
is it [INAUDIBLE]?
LESLIE BRUNETTA: It doesn't
stick in the same way.
Yeah.
So this is a piece of
vertical orb web capture
spiral in a piece of amber
that's 130 million years old.
Yeah.
So there's the line you can see.
And then the droplets are this
protein glue, aggregate silk
protein glue.
The spider lays
it down in a coat.
But because of the chemical
makeup of the glue,
it beads up like that.
So when you see
sparkles on the webs,
sometimes what you're seeing
is water, but a lot of times,
this is what you're seeing.
So the interesting
thing about this
is this means that spiders first
began to build vertical orb
webs back when the
dinosaurs were around,
which seems like an
awfully long time ago.
But that's really late
in spider evolution.
I mean, that's 250 million
years into the story
of spider evolution.
So as I said, these
have the qualities
that I mentioned of the orb web.
The other thing about them is
these are the first spiders
to hang their webs out
in direct sunlight.
And as a result--
well, not as a result,
but associated with
that, they have
interesting optical qualities.
So if we get to Q&A, somebody
should ask why insects still
fly into these things
after 130 million years.
And the evolution
of this new silk
correlates with another
explosion in species.
So like I said, the mesophiles
have about 90 species.
The mygalomorphs, there
are about 3,000 species.
The araneomorphs, there are
now about 39,000 species.
And within the
araneomorphs, this section
of spiders, if you
want to call them that,
outnumbers their closest
relatives by about 10 to 1.
So clearly, what they've done is
that they've gone out, created
new niches.
They were able to move
farther out in branches.
And also, especially,
they are catching
new prey, which is
fast, flying insects.
So if you were like me before I
started working on all of this,
one of the
misconceptions I had was
that there are these kind
of like acmes of evolution,
that the orb web was like this.
And I have evidence that I'm not
the only one who thought this,
because there was a cover
story about those-- the goats
that they were trying to get to
make spider silk which they're
still working on.
There was a cover story in
the "Times Magazine" in 2001.
And part of the story
talked about how
spiders used to do
all sorts of things.
And then they started
making the orb web,
and the rest of the
spiders all disappeared.
Clearly not true.
But in addition to
another piece of proof
that there is not an
acme of adaptation.
I mean, the orb web
is pretty amazing.
But the cobweb, which most
people think is just really
kind of a mess,
in common parlance
is more advanced
than the orb web.
It evolved after the cobweb.
It derives-- I
mean, the orb web.
It derives from the orb web.
And the evidence seems
to show that it evolved
through natural
selection as a response
to the evolution of
spider-hunting wasps.
Spiders' biggest
predators are wasps.
It's really a horrible story
what wasps do to spiders.
They catch them, paralyze
them, lay their egg in them,
and then the larvae
comes out and eats
the still-living,
paralyzed spider.
AUDIENCE: [INAUDIBLE].
LESLIE BRUNETTA: Yes, exactly.
So what you've got here
is you've essentially
got sort of a silk shark cage.
That little orange spot
in there is the spider.
Do you see it?
That's the spider.
So it's essentially
in this shark cage.
And then the other interesting
feature of these webs
is called a gum foot line, which
are these lines coming down.
They're glued down here.
And obviously,
they're under tension.
And so what happens is that
if prey walks by and severs
that glue connection there,
they stick to this line
and get flung up to the spider.
So in addition to the
protective advantage of this,
there's also the
advantage that they
can capture not just flying
prey, but also walking prey.
So just to sum up all of this
and what we've seen here.
So as I said, I'm
not a biologist.
But I've really come
to feel that it's
more and more important
for non-biologists
to understand at
least the really
basic concepts of evolution.
It has a big
understanding in terms--
a big impact in how you do or do
not understand global warming.
All sorts of
ecological questions.
I mean, for instance,
as you learn
this and the scale
of this history,
you understand
that there's really
no such thing as a
balance of nature.
Things are never
really in balance.
Evolutionary concepts have a big
impact on biomedical questions,
including cancer and
the treatment of cancer.
And I have come to
think that spiders
are kind of the vehicle
for explaining evolution
to non-biologists.
So just for instance, I
learned that contrary to my gut
feelings, natural selection is
not some knockout competition
like we saw with Brazil
and Germany yesterday.
There isn't just one winner.
There isn't any acme adaptation.
There is, in fact, no such
thing as being perfectly adapted
to your environment.
I mean, the orb web
is really amazing.
It doesn't help spiders
avoid spider-eating wasps.
So everything is much, much more
fluid than we tend to perceive.
Orb webs and cobwebs are
excellent at catching flying
insects, but the mesophiles are
still fine in their burrows,
as though insects
never evolved flight.
So our ideas of perfect or
ideal or advanced or primitive
are completely
irrelevant to nature.
And that has a lot
of implications
for how we think about ecology.
And I haven't even talked
about the co-evolution
of parasites and pathogens.
I mean, when you get these
micro-- really intense
microscopic views
of spiders, you
see that spiders have mites, and
some of those mites have mites.
So spiders have made
very clear to me
that evolution is aimless.
There's no goal.
If there were a goal, we
would have one or two species
of spiders and not
more than 40,000.
And it's not all
aiming at the orb web.
So I just wanted to say I
hope that you've enjoyed this.
These concepts, these
evolutionary concepts,
actually, once you get
them, are quite simple.
And once you start paying
attention to spider silk,
and even though this is
an incredibly clean room,
I'm sure we could
find some here.
Once you start paying
attention to spider silk,
you start noticing
all sorts of things
that you would never
notice otherwise.
So if you're interested
in a little more about how
the book came about
or some things
that we didn't manage
to get into the book,
you can check out my website.
And this organization,
cpali.org,
is my co-author, Kay
Craig, has started
an organization in Madagascar
based on her knowledge of silk.
That's a conservation
and poverty alleviation
program in Madagascar.
So thank you very much.
And if you have any questions,
I'm happy to answer them.
MALE SPEAKER: Thanks
very much, Leslie.
LESLIE BRUNETTA: Thank you.
MALE SPEAKER: That
was fantastic.
Fascinating.
I know we started
late, but some people
will have 2 o'clock meetings.
So let's have questions
for the next eight minutes,
then let people leave
without embarrassment.
Of course, these are
Googlers, so they
won't be embarrassed anyway.
And then anyone who wants to
stay after that, I'm sure--
LESLIE BRUNETTA: Yeah.
MALE SPEAKER: --if
you're available.
LESLIE BRUNETTA: I'm available.
MALE SPEAKER: Great.
LESLIE BRUNETTA: Yes?
AUDIENCE: As a result
of writing this book,
have you developed any more
intimate fondness for spiders?
Do you keep any
spiders as pets now?
LESLIE BRUNETTA: I don't keep
them, but they like my house.
We don't do a lot of housework.
Yes?
AUDIENCE: So why do insects
still fly into the web?
LESLIE BRUNETTA: Oh, so-- Right.
So there-- maybe this isn't
the right metaphor to use.
But there is this arms race
between the development
of insect vision systems,
which are pretty amazing,
and the optical qualities
of the-- let's see
if I can also find
you a couple of-- OK.
So for instance,
here's an orb web.
The reflectance patterns
in the web, insects
can actually learn.
There have been-- my co-author
started some of this.
There have been experiments that
show that flying insects can
learn not to fly into webs.
If they fly into one,
get stuck, and escape--
which happens a lot--
they will-- most of them
will not fly back
into the same web.
There are some, she said, that
was almost sort of tragically
comical, would keep
flying back in.
But they will learn.
But what happens is you can
see, even to the human eye,
and obviously they
see differently--
a bit differently than
we do, as that shifts,
they're never static.
Because the plants
that they're on
are constantly
slightly shifting.
And so you get these--
the pattern breaks up.
And the insects work mainly
by pattern recognition.
You also get-- this is the
web of a golden orb weaver.
This happens to
be in Madagascar.
But we have these in the
southern states also.
You see how sort of
yellow and golden it is.
AUDIENCE: About how big is that?
LESLIE BRUNETTA:
That was really big.
That was really big.
AUDIENCE: So the spider
itself was a pretty good size?
LESLIE BRUNETTA: About-- not
as big as you would think.
About that big.
So that's golden.
Well, a lot of these insects
are looking for yellow flowers.
AUDIENCE: It's a trap.
LESLIE BRUNETTA: Yeah.
And then here's
another example where
there are a lot of insects.
So you know Charlotte
in "Charlotte's Web"
wrote in her web?
He, White, got that
idea because there
are lots of spiders that put
decorations in their webs.
And it's still kind
of controversial
exactly what those
decorations are about,
whether they're predator
deterrence or prey attraction.
But that's cribellate--
it's aciniform silk
and sometimes cribellate silk
that they're putting on there.
There's different
UV reflectance.
And most insects
are attracted to UV,
because there are UV
stripes often on plants
leading to the
flower and also UV
will often signal
to them open space.
So in this particular
photograph,
what she was trying to show
is that if you look on the--
if you look down here,
this is a grass stock.
And this is a UV photo.
And the reflectance
of these decorations
is quite similar
to the grass stock.
So that's what's going
on, back and forth
between the spiders
and the flying insects.
Yes?
AUDIENCE: I'm sort of surprised
that people would expect
an answer to, is this predator
avoidance or prey attractance?
Like it's something to help
the spider live longer.
LESLIE BRUNETTA: Right.
But it'll be both
of those things.
But the interesting
question is--
so there are a couple
interesting questions.
One is it's a balance,
because their prey are
arthropods with
arthropod vision systems,
and their predators
are arthropods
with arthropod vision systems.
So there's this balance
between attracting prey and not
attracting predators.
I mean, there's a long way
to go before we figure out
what's going on with this.
And also, my suspicion,
just because there's
such a huge-- thousands and
thousands of these species--
it's probably different
in different cases,
depending on where
they are and what
the particular environment is.
Yeah?
AUDIENCE: For some
animals [INAUDIBLE]
the other motivating factor
for changes in what they do
is reproduction.
Do spiders also do special
stuff with their--?
LESLIE BRUNETTA:
Ah, spider sex is--
so there are a couple of
things about spider sex.
First of all, nobody
has quite figured out
why they've evolved-- the males,
at the front of the spider's
body there are pedipalps.
And the males have
these modified feet
called palpal organs.
So what they do before they
mate, the male spiders go out.
They go upside down, let's
say, between a couple
of rocks or something.
They spin a little web,
called a sperm web.
Then they deposit
the sperm on the web.
Then they suck the sperm
or draw the sperm up
into these palpal organs.
And then they go
looking for a female.
And so these palpal
organs are what
they insert into
the female spiders.
So now there's also a
problem, because they're also
very sexually
dimorphic, spiders.
Which means that there's
a big difference in size.
The females tend to be giant,
and the males tend to be tiny.
And they tend-- this whole
idea that the females always
eat the male is not true.
Again, because there's
so many species,
there's a huge variety
of things that happen.
And so these mating practices
between different spiders
are, like, all over the place.
There's a certain
amount of cannibalism.
There's a certain amount of-- I
forget the right term for this,
but basically, the
palps go into the female
and then break off, which
then prevents other males
from inserting their palps.
There are males who the
female will be on her web,
and the male will figure out a
different pattern of vibrations
to put on the web so that
she recognizes him as a male
and not as prey.
So there's-- that's a
whole other lecture.
And actually, I don't--
I'm not an expert in that.
But there are people who are.
MALE SPEAKER: OK.
Let's-- it's almost 2 o'clock.
Let's thank Leslie
again for coming.
