"SPIDERS!"
Season 905

Teaser
Episode Open
Spin, Spin, Spin
Song and Dance
Spider Canyon
Amazon Tales
Arachnophobia

TEASER

ALAN ALDA There are spiders… and then there are spiders.

ALAN ALDA (Narration) Rosie the tarantula isn't even the biggest… or the ugliest. Dancing spiders… aggressive spiders…even cyberspiders. Spiders in their webs…

ALAN ALDA What happened?

ALAN ALDA (Narration) Spiders in the jungle. Virtual spiders… to cure arachnophobia.

ALAN ALDA Oy! This is the first time I've been able to scare a spider. I'm Alan Alda. Join me as Scientific American Frontiers explores the slightly sinister world of spiders.

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EPISODE OPEN

ALAN ALDA When I was a kid in California, I once found a tarantula in the shallow end of the family swimming pool, and I panicked. I didn't know what to do. I started frantically and clumsily to kill it. It was a disturbing experience, and ever since, spiders have made me kind of uneasy. You know, all those angular, sometimes hairy legs; the way they scuttle out of the shadows, clearly heading straight up your pants' leg; the feel of a web suddenly draping itself across your face. So an hour program devoted to spiders? Are they kidding? Well, once I got to know them, it turned out that spiders are among the world's most amazingly inventive creatures. And now, I not only find them interesting, but with the help of a fellow arachnophobe, I finally made my peace with a tarantula.

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SPIN, SPIN, SPIN

ALAN ALDA (Narration) A web glistens in the early morning sun in a field in Denmark. My companion, from the nearby University of Aarhus, is Fritz Vollrath.

ALAN ALDA Have you seen anything here?

ALAN ALDA (Narration) Fritz wants to know how orb-web spiders plan and build such exquisite structures.

ALAN ALDA I see, oh yeah, it's very big

FRITZ VOLLRATH Wonderful. It's gigantic.

ALAN ALDA Is that the spider up there?

FRITZ VOLLRATH Yeah, that's the spider. Shall we get her out?

ALAN ALDA (Narration) The web was built by a very pregnant female lurking at its corner.

FRITZ VOLLRATH There she goes. A bit of water…

ALAN ALDA (Narration) Fritz sprays the web with water to make it more visible.

FRITZ VOLLRATH Ah ha, she's interested in the fly, and the water…

ALAN ALDA (Narration) But -- perhaps because she's pregnant and feels vulnerable out on her web -- she beats a hasty retreat.

ALAN ALDA Are we disturbing her at all?

FRITZ VOLLRATH Yes I think so. They have very long hairs on their legs.

ALAN ALDA And they hear with them?

FRITZ VOLLRATH They hear with their legs. We can have a look at one of the other spiders and clap our hands and you can see how they can hear. Oy!

ALAN ALDA Oh yeah, yeah, when you said "oy".

FRITZ VOLLRATH Oy!

ALAN ALDA Look at that.

FRITZ VOLLRATH Oy! Oy!

ALAN ALDA It's a cockney spider.

FRITZ VOLLRATH That's right. And it's not my breath see? Oy, oy, hello spider!

ALAN ALDA Yeah, it's not the air, it's the sound. Woo-woo. Woo-woo. Oy! Oy! This is the first time I've been able to scare a spider!

ALAN ALDA (Narration) Orb webs like these -- the classic spider webs -- are built anew every night in just a half-hour or so of labor.

ALAN ALDA I see a web there.

FRITZ VOLLRATH Oh yes, look at that.

ALAN ALDA (Narration) At first sight, this one also seems unoccupied.

FRITZ VOLLRATH Ah, she has a huge fly. No wonder that…

ALAN ALDA Oh she's having breakfast.

FRITZ VOLLRATH Absolutely.

ALAN ALDA There she goes.

ALAN ALDA (Narration) The spider is the common garden cross spider.

FRITZ VOLLRATH There she is. You can see lots of little new insects flying into the web.

ALAN ALDA (Narration) The orb web is the perfect device for catching flying insects, like the fly she's eating now. But spiders had found a use for silk long before insects even had wings.

FRITZ VOLLRATH They invented silk about 400 million years ago, long time ago they invented silk. And possibly to cover the eggs maybe, or wallpaper a little burrow in the sand that they had.

ALAN ALDA You mean all this comes from interior decoration?

FRITZ VOLLRATH That's right. And then of course once you have silk you can do things with it. For example, you can make single threads that go out from your wallpapered little house, and an insect that walks around stumbles on one of these threads and the thread gives you the information that there is somebody out there. It's a line on which you have your feet, and you can feel somebody tugging it and you rush out a go for it.

ALAN ALDA (Narration) When insects discovered flight, spiders followed them into the air, spinning their snares into webs to catch insects on the wing -- as well as careless ants. The spider's silk now has another role -- wrapping the prey, which has been paralyzed with a venomous bite, for eating later. This wrapping silk is actually one of seven silks this spider spins from glands in its tail. Another of these silks, a strong non-sticky thread, is used to build the frame of the web, the supporting spokes. Then the spider sets about spinning the silk that will actually catch her prey -- but not quite as I'd always imagined.

ALAN ALDA Is all this a spiral? Does it start with just one line out from the center and go round and round?

FRITZ VOLLRATH That's right. But starting from the outside.

ALAN ALDA The outside?

FRITZ VOLLRATH Now this is… The problem that the spider has is that it has to build a structure that has to be very sticky and reasonably soft. If it is too tight, then it could act like a trampoline. When an insect flies in it, it is flung back out. So it has to be quite soft and quite giving. But now imagine, working, precision working, on a trampoline. It's difficult to do that because everything moves. So what the spider does, it has a little pretty tough spiral, from the inside out. And then it builds from the outside in the sticky spiral and eats the structural spiral away.

ALAN ALDA Wow.

FRITZ VOLLRATH That means that it ends up in the center, surrounded by a pristine web.

ALAN ALDA (Narration) Soft yet sturdy, the web can even survive being poked and torn.

FRITZ VOLLRATH You can see the rest of the structure is hardly affected by it. It's a perfect lightweight structure in which the tensions and forces are distributed in such a way that local damage does not result in total failure.

ALAN ALDA You just touch it?

FRITZ VOLLRATH Just touch it and…

ALAN ALDA Oh! What happened? It thought I was a fly!

ALAN ALDA (Narration) Fritz is especially intrigued by how the spider constructs its sticky capture spiral. Orb spiders have very poor sight, but they seemed to him to be using their legs and bodies to make measurements of distances and angles. By slowing down the video, you can see for instance how the left front leg reaches out to touch the previous spiral before the spider attaches the new one. But just how does the spider turn measurements like these into decisions? Fritz assumed that spiders possess some inborn set of web-building rules. The trick was to figure them out.

FRITZ VOLLRATH What we decided to do there is to take the rules and encode them into a robotic spider.

ALAN ALDA Some little imaginary spider that just exists on the screen.

FRITZ VOLLRATH Exactly, a robot that exists in the screen, so we don't have to worry about the little wheels and the legs and everything actually working and being oiled. The thing just lives in the screen. But it is like a robot. It uses the brain of a robot.

ALAN ALDA (Narration) Enter the cyberspider -- whose brain has to figure out for itself how to lay down the capture spiral, using rules Fritz and his colleague made up. This cyberspider's an expert, reversing direction to keep its web spacing even -- and like its living counterpart, eating its scaffolding as it goes. But most of the rules the researchers tried out produced thoroughly incompetent cyberspiders. So they turned to the method used by nature.

FRITZ VOLLRATH Instead of us looking at our computer cyberspider and changing part of the rules and how the rules interact, we actually programmed that into the life of our cyberspiders -- because we don't have just one, we have many.

ALAN ALDA You're not telling me you get these cyberspiders to mate?

FRITZ VOLLRATH Absolutely.

ALAN ALDA They meet each other in chat rooms and get together?

THIEMO KRINK And they migrate. They meet each other in cyberspace. It's true. Actually on the screen…

ALAN ALDA Little spider bars. How do you actually get two cyberspiders to mate? What's the real process you go through?

FRITZ VOLLRATH Ah well, we have several cyberspiders in there that build webs. These webs -- using their rules -- these webs catch prey…

ALAN ALDA What, do you randomly toss in insects and then you see how many it catches and you add them up and it gets points for that? Then it becomes a valuable cyberspider, it's a smart cyberspider.

FRITZ VOLLRATH A good one with lots of prey is a good one and one with very little is a bad one. Now the good ones -- there are many -- the good ones mate and have children which inherit their genes.

ALAN ALDA (Narration) Here are six webs built by one generation of cyberspiders. Each spider has a random selection of cybergenes, and so different web-building rules. Now the web is sprayed with cyberprey-- both small and large insects -- and the spiders that catch the most pass on their cybergenes to the next generation. Just as happens in nature, some of the genes pick up mutations as they're passed along.

ALAN ALDA How do you know how much mutation to put in?

FRITZ VOLLRATH We put in… you have to be a bit clever about that. If you put in too much you get, you know, monster spiders…

ALAN ALDA Monster cyberspiders. Ah, this is getting good now…

ALAN ALDA (Narration) But with just enough mutation to generate novel new genes, the webs keep getting better and better.

ALAN ALDA This is wonderful. You have a window here -- on the same kind of computer screen that I have on my desk, you have a window into evolution. You're watching evolution take place, at least a model of evolution.

ALAN ALDA (Narration) This is how one population of cyberspiders evolved their web through time. Amazingly, Fritz and Thiemo believe that only two key rules, involving angles and distances, govern this web-building ability -- a marvelous example of how simple rules can combine and interact to produce very complex things. This web evolved in just 50 generations. What the work suggests, but of course doesn't prove, is that real spiders also build their webs using these same simple rules -- creating in the process not only a device to catch prey, but also an instrument for serenading the opposite sex. Fritz is hoping this male will demonstrate, by plucking out a love song on the threads of the web built by the female at its center.

ALAN ALDA He just seems like he's sitting there limply. He doesn't seem to be engaged at all.

FRITZ VOLLRATH He's limp with fear maybe. He has to figure out where he is in relation to her, exactly where in the web he is. But he also knows the only way to find out is to walk around.

ALAN ALDA And if he walks around he's in danger of being eaten.

FRITZ VOLLRATH Exactly.

ALAN ALDA Now what's he doing? He's moving his feet, his legs.

FRITZ VOLLRATH Yes, he might start to play…

ALAN ALDA (Narration) Our male's tentative plucking of the female's web-strings wasn't unsuccessful, and he ignored Fritz's urgings to try again. But as we'll see in our next story, the signals a web can transmit don't always serve the spider's interests -- they can also lure it to an untimely end.

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SONG AND DANCE

ALAN ALDA (Narration) In a greenhouse at Binghamton University in New York State, Stim Wilcox is setting up to record a fatal confrontation between spiders -- one in its web, the other -- called Portia -- about to be released from her plastic bucket.

STIM WILCOX This is called a Portia Palace of course…

ALAN ALDA (Narration) The Portia spider is a hunter -- of other spiders.

STIM WILCOX It's amazing, they just sort of lock on like warriors, with prey in sight and sword raised.

ALAN ALDA (Narration) Now everything happens very fast.

STIM WILCOX: She's signaling. It's perfect. She's stalking. God! She pounced the prey! If you got that on film, we've got it.

ALAN ALDA (Narration) We're about to find out what just happened. But first here's Portia alone in all her bizarre beauty -- with headlamp eyes that shine out from a brain filled with cunning.

STIM WILCOX: The first step to record is to put the recording device on the webbing. I've got here a galvanometer with a little stylus…

ALAN ALDA (Narration) The needle will pick up the tiniest vibrations of the web. It allows Stim to literally hear every footstep of the spider that lives here. But it's the Portia that Stim really wants to listen to -- because it's the way she exploits the web to transmit messages that makes her such a mistress of deceit.

STIM WILCOX OK, Portia's on the web…

ALAN ALDA (Narration) Found most commonly in Australia and Southeast Asia, Portia spiders don't build webs of their own, but invade the webs of others. Her arrival on this one hasn't gone unnoticed. Portia's goal is to get close enough to her host to attack and kill it.

STIM WILCOX Portia when on a web like this tends to look up and stare fixedly at you for maybe five to ten minutes before doing anything else. So I'm just going to try to stay still while Portia orients herself and decides what to do.

ALAN ALDA (Narration) It's a high stakes game. Every move she makes sends a message -- and the wrong message could get her killed. The trick is to send a signal that tempts her host to investigate but not attack.

STIM WILCOX Portia is now beginning to move around and make palp plucks with her two little apparent legs up front, and is in fact signaling that way to try to lure the prey spider up close to it.

ALAN ALDA (Narration) But this time the strategy doesn't work. The host spider panics -- and Portia switches its tactics.

STIM WILCOX The left front leg there was making signals.

ALAN ALDA (Narration) Instead of gently plucking the web, it starts to twang it with its front legs.

STIM WILCOX Notice it's starting to move forward just a little bit. When it makes these larger jolting signals, the whole body moves. It becomes what we call a smokescreen signal, because the frequency that Portia's body makes when it shudders like you can see there is virtually identical to the waveform made when a leaf or a twig drops into the web.

ALAN ALDA (Narration) By moving forward as it shudders, Portia hides its advance behind what seems to the host spider to be a bombardment of flying objects. It's this ability of Portia to change tactics in mid hunt that Stim Wilcox finds so impressive. He's recorded a repertoire of some one hundred different signals from Portia -- which often tries out first one, then another, till it finds one that works. This time the smokescreen signals have brought it within jumping distance of its by-now thoroughly confused host.

STIM WILCOX See the front legs come up? Like so -- raised up high like that, higher and higher. They're way up high ready to… JUMP. Perfect! Absolutely perfect.

ALAN ALDA (Narration) Every time he witnesses Portia's prowess, Stim Wilcox almost glows with pride.

STIM WILCOX They are amazing little dynamos of cleverness, deceit, problem solving, thinking and just plain flat-out instinct. As a research animal, just from a strictly scientific viewpoint, it's a dreamboat animal. It's got it all.

ALAN ALDA (Narration) If Portia's got it all as a research animal, then this -- another of the class of spiders called jumping spiders -- runs it a very close second. It's a female Maevia, sharing with Portia a huge pair of eyes up front and three smaller eyes on each side. Here's a male Maevia, with grey stripes and bright orange-yellow pedi-palps -- mouthparts that look like extra legs. When he courts the female he scuttles from side to side in a ritual shaped by evolution to let the female know he's a potential mate and not a meal. Now things get strange -- because this is another male Maevia, black and white with three tufts on his head. When a female's around, he too does a mating dance, but his is a sort of "hey, look, I'm over here!" Only after he gets on OK signal from the female does he sidle in for the final approach. Dave Clark of Alma College in Michigan has built a miniature movie theatre to find out how female Maevias cope with having two very different males in their lives.

DAVE CLARK She's orienting around the arena. Now she's looking up at me, kind of checking me out. We're looking eye to eye at each other right now. And hopefully she'll re-orient to the grey morph that's courting her. There, just like that.

ALAN ALDA (Narration) What the female is actually watching is a video image of the grey-striped male. Dave Clark discovered that spiders treat small-screen versions of their kind like the real thing when he was one day watching spider movies projected on the wall of his lab.

DAVE CLARK: I noticed that a female in her cage had swiveled and oriented to the image on the wall. In fact she ran down to the end of her cage and displayed full blown sexual receptivity behavior to that male image. And I thought, wow, this is pretty neat.

ALAN ALDA (Narration) In real life, half the male Maevias are born grey and the other half tufted. At the movies, females are happy with the video versions of either. This gave Dave an opportunity to ask a question that had long intrigued him. What are the females responding to -- the way the males look, or the way they act? He turned to his computer.

DAVE CLARK Here we have our tufted in his phase one posture. This is all just little objects in here that you use to create these and piece them together, sculpt them together into a spider-like shape that you see there. You can also animate these images as well. Here's a 3-D animation of a tufted male in phase one courtship. You can do the same thing with our grey male, animate our grey male. This also provides quite a bit of flexibility in how you might go about changing the appearance of these images. And here's our tufted assuming a posture that it would never assume in nature.

ALAN ALDA (Narration) The tufted is in fact behaving like a grey. And this grey is waving just like a tufted. Dave can now show these mixed-up males to females in his spider theatre. Most females are unimpressed by the tufted males that behave like greys. On the other hand, they are clearly interested in grey males that act as if they're tufted. So for the tufted males, it's their vigorous waving that seems to count rather than their hairdos -- which fits with the fact that they do their courting at a much safer distance from the females than do the greys. Right now both males seem equally successful in their strategies. But Dave suspects that he may be watching one species in the act of separating into two -- a magical moment in evolution that may also be crystallizing in the next spiders we meet.

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SPIDER CANYON

ALAN ALDA (Narration) We're in Southern Arizona. After the brief summer rains, the desert's deceptively green. This is a harsh environment, posing extreme challenges to the plants and animals that live here.

RIECHERT Usually what we have is a sort of a permanent sheet that's kind of large, because these are hungry spiders.

ALAN ALDA Could they be anywhere?

ALAN ALDA (Narration) I'm again looking for spider webs -- this time with Susan Riechert of the University of Tennessee, who's been studying the spiders here for 30 years.

ALAN ALDA There's a... there's a web.

RIECHERT Yep, see, you did better than I did.

ALAN ALDA (Narration) It's a funnel web, a flat sheet of silken webbing extending like an apron in front of the spider's funnel-shaped lair.

RIECHERT They're touching the web and they're feeling the vibration of anything that might be coming down the web. In addition they're... picking up airborne vibrations of flying insects that are moving the air. And so they can tell what kind of insect that is that's in the vicinity and um... whether they want to come out and attack it or not.

ALAN ALDA They can tell just by the vibrations on the web or... or in the air what kind of insect is sitting on their trap, huh?

RIECHERT That's right.

ALAN ALDA (Narration) These are fire ants. They're tough and aggressive, with a nasty bite.

RIECHERT Here we go. I'm dropping the ant.

ALAN ALDA (Narration) The spider attacks without hesitation. It's a female -- summer is breeding season so she has to eat, even though she's risking her life in the process.

ALAN ALDA She grabs at it then she pulls back.

RIECHERT That's right.

ALAN ALDA What's she doing when she does that?

RIECHERT She's trying to avoid the jaws of that ant. She's trying to inject venom. Oh... she has to try and get her little fangs that are very small in through that hard casing of the ant.

ALAN ALDA (Narration) But it's not just the ant that could kill her -- the hot desert sun could, too. She'd be protected back in the shade, but she can't take her prey in until it's subdued and safe to move. Five minutes into the struggle the sun comes out. As the web rapidly heats up, the spider's forced to retreat to its shady funnel. It's now over a hundred degrees out on the web.

ALAN ALDA How does she know the ant will still be there when she comes back?

RIECHERT She doesn't. But she doesn't have a choice, because if she heats up and she goes into a stupor she'll die... she'll get... she'll cook. But they're hungry so they have to try for everything.

ALAN ALDA (Narration) She's back within a minute for a quick check on her victim. Now it seems safe to take in. Susan thought she had her desert spiders pretty well figured out until one day she discovered the spiders who live up in this canyon. The canyon's a lush oasis, so biologists would expect the plant and animal species living here to be different from the ones coping with desert extremes. But to Susan's surprise, the spiders were the same. This launched her on a journey of discovery that's still continuing, and that may eventually lead to a glimpse of evolution itself in action.

ALAN ALDA Well this is a lot nicer here. I mean, I can see how the spiders feel about this...

RIECHERT It's better for us, isn't it?

ALAN ALDA Yeah, but I... I can... it's cooler.

ALAN ALDA (Narration) Susan first noticed that, even though it's cool here, river spiders often stay in their funnels. They're timid and fearful, unlike their desert cousins. That makes sense, she realized, because under the trees the enemy's no longer the sun -- it's hungry birds. But seeing the same species changing its behavior like this, to fit a different environment, was a big surprise -- an important discovery in biology.

RIECHERT Let's try an ant, shall we? Let's see... do you see her at all? If she's there, she's back pretty far.

ALAN ALDA I see something in the tunnel.

ALAN ALDA (Narration) The threat of birds stops river spiders coming out to fight a tough ant. There are plenty of softer insects around anyway.

ALAN ALDA There's a definite lack of interest in this ant here.

RIECHERT They're gonna ignore her... the vibratory patterns that an ant's gonna make. They're not gonna come out...

ALAN ALDA It's not worth the trouble, because you could get killed that way.

RIECHERT Yeah.

ALAN ALDA (Narration) Susan set up a natural laboratory -- an eight-acre enclosure running from the river up the canyon side. At the top the lush river environment gives way to dry woodland, where the spiders are very aggressive -- like those in the extremes of the desert. For Susan the question was, what happens when the tough guys above meet the softies below? The first thing that happens is any spiders heading down into the canyon are stopped by the border patrol. They come up against the study area's boundary, and get caught in pitfall traps.

ALAN ALDA I'll check the ones coming from this side...

RIECHERT We'll see who finds the first animal, how's that?

ALAN ALDA ... all right.

ALAN ALDA (Narration) Both sides of the fence are checked, but most spiders are heading downhill toward the easy life on the river.

ALAN ALDA Ah... there's something in here... oh.... oh geez... watch out, there's something in there!

RIECHERT Yeah, a cricket or something.

ALAN ALDA What? A cricket?

RIECHERT A cricket, and an itsy, bitsty spider, and...

ALAN ALDA You never know what it could have been. It could have been a scorpion.

RIECHERT Well, you're losing out on...

ALAN ALDA I don't want it back!

RIECHERT I emptied it.

ALAN ALDA Oh.

RIECHERT You always have to empty all the insects out... when you do this.

ALAN ALDA You know...

RIECHERT By... by the way, there are scorpions... um...

ALAN ALDA There are or aren't?

RIECHERT There are.

ALAN ALDA There are. Of course there are! What do you think I was screaming about?

RIECHERT So watch your fingers when you reach in.

ALAN ALDA Nothing... something, something! Huh-huh, a spider...

RIECHERT Yeah, probably another cricket...

ALAN ALDA No, no, a spider.

RIECHERT Oh yeah?

ALAN ALDA Yes.

RIECHERT Let's see. What kind?

ALAN ALDA Very aggressive spider... ha... That's a spider!

RIECHERT Oh.

ALAN ALDA What is it?

RIECHERT Well, that is an Agelenopsis aperta.

ALAN ALDA I told ya!

ALAN ALDA (Narration) Every day trapped spiders are brought to the lab close to the enclosure. They'll be returned to the wild just across the fence, at the point they were caught, to continue their journey. But first they're put through their paces. This is a test for aggression. Two males are placed on a web built by a female who's been removed. Immediately one male takes possession of the web funnel, looking for the female. Susan's seen this kind of face-off many times in the wild. The result can be anything from one spider running away, to a fight to the death. These are both aggressive, dry-land spiders so neither is prepared to back down. In fact, after he's first driven off, the attacker heads right back to the web funnel. Inside the funnel the defender slowly edges toward the attacker, who's lurking just outside. They're both looking for a fight. When it finally erupts it's ferocious. In a surprise reversal the attacker, now on the left, bites the defender's leg and hangs on -- it could be all over. But then the defender pulls free, scares the attacker off and pauses to nurse his leg. He once again takes possession of the funnel. But it's not over yet. The defender wants the attacker well clear of the area. But the attacker stays lurking nearby. This particular confrontation took about two hours, although Susan's seen them run for an entire day. The end came like this -- with a vicious tangle that was going to lead to death, until the referee stepped in.

RIECHERT I've got them separated.

ALAN ALDA (Narration) Susan doesn't want to lose any of her spiders. The aim is to score them for aggression, mark them, and then see how they do back in the enclosure. The contestants will be returned within the hour. There are about fifteen hundred spiders within the enclosure, and Susan has caught and tested every one. Females are kept in the lab until they build webs in their plastic boxes, then they go back in the field with the males. Now the study moves to the next stage.

ALAN ALDA You know exactly where it is?

RIECHERT Ah... yes.

ALAN ALDA It's like, there's a favorite night spot they go to or what?

RIECHERT Um... no, well, potentially any one of these spiders that is in a box could be mating. Now, I think if you were to look inside that funnel you will see...

ALAN ALDA Down in here?

RIECHERT Yes, you will see that there are two spiders.

ALAN ALDA Oh, yeah yeah. OK.

ALAN ALDA (Narration) There's a mating going on between an aggressive, dry-land male who came down the hill, and a timid river female. It would have gone something like this, with the male cautiously approaching while doing his mating dance, to signal his intention to the female. Both spiders have to be careful because things can turn ugly pretty quickly. A fight could start, especially if male and female are very aggressive. Or if one's too aggressive and the other's too timid, then the timid one might simply run away. But in this case wedding bells ring out and the tough, dry-land male wins his shy bride from the river. The happy couple will be blessed with about three hundred kids. Susan's been following the spiders in her enclosure for twenty years now and she's run into a puzzle -- the spiders just aren't behaving right.

ALAN ALDA Right there?

RIECHERT Yeah.

ALAN ALDA (Narration) Many spiders are much more aggressive than makes sense here. Susan's figured out they are the hybrid offspring of aggressive, dry-land males and timid, river females.

ALAN ALDA That really seems aggressive. You think that's a hybrid?

RIECHERT It's gotta be. I mean, here's a spider that obviously isn't hungry. She takes these ants, that could kill her, into her funnel and she lets them go.

ALAN ALDA Just catching them for no reason? And they're dangerous to catch?

RIECHERT And she probably won't even eat it.

ALAN ALDA (Narration) Here's the kind of super-aggressive behavior by the hybrids that Susan discovered. Dangerous fire ants are pulled into the funnel without first being subdued. Not even a hungry desert spider would take this risk, and sure enough, Susan's found most hybrids don't make it. Many are taken by birds, many don't breed because they scare off their partners. So now Susan predicts a new behavior will evolve among the river females, that prevents them from mating with aggressive males. The offspring of those females would survive, unlike hybrids. If she's right, she'll see much more of this -- a male with no partner.

RIECHERT Hey Terry!

TERRY You got something Susan?

RIECHERT Yeah I'm at A134 and I have a male. It looks like ah... white, yellow, pink...

TERRY He was there last check.

RIECHERT The female is... ah, not here, so he must have chased her off.

ALAN ALDA (Narration) Susan expects that somewhere there's a timid, river female who won't mate with an aggressive male from up the hill. Her offspring will inherit that behavior, they'll thrive, and eventually they'll take over the canyon. They'll never mix with the guys up the hill again. It'll be a shift to a new species of spider -- evolution in action. To make that discovery Susan Riechert's prepared to put in another few decades.

ALAN ALDA Do you ever at night before you go to sleep say to yourself, wouldn't it be great if in the next few months I started to see this shift.. and I... I was there to experience it?

RIECHERT Oh... we'd all love to have that kind of... ah.. event happen. But... that's nature. It does what it wants. Whatever happens, happens, and we can just follow it.

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AMAZON TALES

ALAN ALDA (Narration) A tributary of the Rio Napo in Ecuador -- itself a tributary of the Amazon. In a journey that moves from motorized canoe to dugout, two arachnologists are doing what arachnologists love most -- searching for spiders. Letitia Aviles was born in Ecuador. Rick West is here from British Columbia. And this is one of the biggest spider webs in the world.

LETITIA AVILES This is a pretty good size nest, not the largest one I've seen.

RICK WEST Looks like it's about 10 or 12 feet across.

LETITIA AVILES One can estimate how many spiders there are in there by measuring the cross section of the nest, and there is a very good correlation between the number of spiders in the nest and the cross-section.

RICK WEST How many individuals would you estimate would be in that?

LETITIA AVILES Yeah, I imagine this colony might have between five and eight thousand spiders in it.

ALAN ALDA (Narration) The spider is Anelosimus eximius -- out of 39,000 known spider species, one of only 17 that live together in colonies. This nest has webbing that stretches 20 feet or more up into the surrounding trees.

RICK WEST Within the one colony, are all the individuals related?

LETITIA AVILES Yes, they are. The colonies get initiated by sometimes just a single female. And then they remain within the nest until they mature and then they mate with nestmates.

ALAN ALDA (Narration) Letitia Aviles began studying these spider colonies when she was a graduate student.

LETITIA AVILES It's really wonderful to be working on an organism that happens in my country, especially to have started working on them while I still lived in Ecuador, because I was able to come to the field year round as frequently as I wanted and that way I got to learn a lot of things about their lifestyle that I don't think I would have been able to figure out if I'd been coming here only for a month every year. And with that basis, now that I live in the States, I already know enough of the biology to know what it is that I can do and cannot do with them.

ALAN ALDA (Narration) On this visit, Letitia and her graduate students are doing an experiment to find out why some colonies grow large, others stay small, and still others abruptly go extinct. The spiders from this colony are destined for a new life elsewhere.

LETITIA AVILES I think this colony contains mostly adults and some small babies.

ALAN ALDA (Narration) The experiment begins with sorting the spiders into different age classes -- and then counting them -- one at a time. These are adult females, which usually outnumber males ten to one. Deep within the forest, Letitia plans to release some of the captured spiders to see what sort of new colony they build.

LETITIA AVILES We're going to put them a little bit below so that when they start building they're going to build up.

ALAN ALDA (Narration) She starts with juvenile spiders, which immediately and enthusiastically begin laying out the silken threads of a brand new nest. And almost at once, they claim their first prey. Next come the adults, which join in the frenzy of new construction. We'll check back later to see how Letitia's new nest is progressing. Meanwhile, Rick West is off in search of his favorite spider.

RICK WEST A lot of frogs and cockroaches in here so there's a good food source. Also, they like to use burrows around the buttress roots of these trees. Ah, there's a nice burrow. And it's got a big tarantula in it, too.

ALAN ALDA (Narration) Rick digs with his knife at the back of the tarantula's burrow.

RICK WEST …something to prod her out. There she comes. What a beauty.

ALAN ALDA (Narration) He's handled hundreds of tarantulas -- and so far has never been bitten.

RICK WEST This tarantula is an adult female. It's Megaphobema velvetosoma. Near the front of the underside of the body you can see the fangs, There's two of them. They're about half an inch. And they're used for stabbing -- they actually stab their prey.

ALAN ALDA (Narration) The back of the tarantula is covered with tiny hairs, barbed like harpoons.

RICK WEST When they're scraped off -- she uses her rear leg and there are some very stout spines -- and she'll scrape these over the top of her abdomen very quickly and cause these hairs to scrape off just like I'm doing here. And you can see them floating away here. And those float in the very fine air currents set up by the legs and, boy, I'll tell you, when these land into your skin, they cause a great irritation.

ALAN ALDA (Narration) While Rick's been showing off his tarantula's weapons of attack and defense, Letitia has been checking her brand new spider colony.

LETITIA AVILES Oh, it looks like they did pretty well. They have been working, it's less than 24 hours since we set up the spiders, and they have already built a complete nest.

ALAN ALDA (Narration) The nest includes a huge skein of webbing reaching up into the trees. Its job is to capture prey for the nest's inhabitants.

LETITIA AVILES Oh, they've caught some prey overnight, and there's a group of spiders feeding on it right now. And it's not necessarily the same individuals that caught it that are going to feed on it.

ALAN ALDA (Narration) This ability to capture and transport much bigger victims than a single small spider could may be one reason for the spider's collectivist lifestyle. Unlike social insects, these spiders don't have specialized tasks within the colony -- everyone does everything. The thousands of individuals in each nest stay together throughout their lives and through the generations -- with just occasionally a single female or small group setting off into the outside world to found a new, daughter colony. Letitia wants to know when, why and how this decision to found a new nest gets made: questions she hopes this colony and others she is setting up in different parts of the forest will one day help answer.

RICK WEST I'm just going to examine this burrow. There's a silken tube on the side of this tree and it looks like it's occupied here.

ALAN ALDA (Narration) Rick is off climbing trees, armed with a tiny video camera.

RICK WEST Looks like there's a nice large female. Looks like she's coming down the burrow now. She senses the camera as a possible intruder and she's coming to defend herself.

ALAN ALDA (Narration) Frustrated, the tarantula turns from attack to defense.

RICK WEST She's turning around. She's going to cover her entrance with silk.

ALAN ALDA (Narration) This is a task tree-dwelling tarantulas routinely perform during daylight hours, sealing their burrows not against prying cameras but parasitic wasps. But with tarantulas, there's always that one big question.

LETITIA AVILES You seem to not be worried about the tarantula biting you. Is it unusual for a tarantula to bite?

RICK WEST It sounds morbid, but I've tried to find at least one human mortality from a tarantula bite, and there's none. If it bites you, the pain is purely mechanical at first and then there's a burning sensation -- I've been told, I've never been bitten -- but I've been told that the burning sensation lasts for two hours and then goes away. So this is an Ecuadorian spider, you're an Ecuadorian lady, is this the first time you've held a tarantula?

LETITIA AVILES It is the first time I've held a tarantula. A lot bigger than the spiders I work with. Like a teddy bear walking on you actually. Pretty soft.

ALAN ALDA (Narration) Rick West can't resist trying to infect everyone he meets with his enthusiasm for tarantulas. But he's about to meet his match.

RICK WEST This is Rosie. She's a Mexican red-kneed tarantula. This particular species is protected by law, you can't capture them in the wild and sell them for the pet trade.

ALAN ALDA What do you do with a pet like this? You can't put a leash on it and take it for a walk.

RICK WEST It doesn't bark or chase cars, I know, but they make the ideal apartment pet, I've heard. You can give it a cricket and a cup of water and go away for a month and come back, it's fine. But, bottom line is, it's just a large spider.

ALAN ALDA (Narration) But for Rick, apparently not large enough.

RICK WEST This is one of the largest tarantulas in the world. She comes from Venezuela. She is a little nasty, you can't handle her. But when you think of her as a spider, it's absolutely unbelievable.

ALAN ALDA I don't know which one to worry about. Now I'm not worried about Rosie so much. This is very clever of you. That is a big animal.

RICK WEST Isn't that something?

ALAN ALDA Would he attack this other spider?

RICK WEST Yes, and actually kill it and consume it.

ALAN ALDA (Narration) And as if I'm not sweating enough already, here comes another one, recently discovered by Rick in Mexico, and named by him, astonishingly:

RICK WEST Hapalopus aldanus, and I named it in honor of yourself. And here…

ALAN ALDA I'm shocked.

ALAN ALDA (Narration) Rick obviously doesn't know of my history with tarantulas.

RICK WEST And at the back it's got what the species name is and a little bit about it.

ALAN ALDA Fantastic. Hapalopus aldanus. If you had named any other species after me I'd be delighted and have this little inner glow. I'm sorry to say -- since this is your life's work -- with a tarantula I have completely blotted it out of my mind, and it's only been two minutes now since you've named this species after me. I'm really sorry.

RICK WEST Well, that's it, I'm disconnecting the mike, we're out of here!

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ARACHNOPHOBIA

ALAN ALDA (Narration) A day in the life of an arachnophobe.

JOANNE SAKELARIS That would be my standard gear regardless of what time of year it was. When I did laundry, the moment that I got them from the drier I would put them in a plastic bag. I had the cleanest truck because I had a spider brush and I would literally brush my truck every single time I got in it. I had also a special spider brush and I would like wave it around in case there were webs hanging on the wall all the way down the hall to my bedroom.

ALAN ALDA (Narration) For Joanne, avoiding even the slightest glimpse of a spider had become a full-time obsession.

ALAN ALDA You tried a number of things, right? And then what? How did you get the idea to work on virtual reality?

JOANNE SAKELARIS Well I saw Scientific American Frontiers on Channel 9, with you…

ALAN ALDA The room is tilted…

ALAN ALDA (Narration) In the show Joanne saw, we visited researchers at Georgia Tech in Atlanta. Using virtual reality, they are able to give people with a fear of heights a simulated version of the real thing.

ALAN ALDA Oh, you know what I hate is looking up.

LARRY HODGES That's what I've always said.

ALAN ALDA (Narration) The idea of VR therapy is to provoke the anxiety of the phobia, then help the patient cope with it.

BARABARA ROTHBAUM You want to give me a rating?

CHRIS CLARK Twenty-five.

BARBARA ROTHBAUM Just because you feel something in your body when you're up this tall doesn't mean that it's fear; just means you're human.

ALAN ALDA (Narration) After several sessions of VR treatment, our patient was even able to take a ride in a glass elevator.

ALAN ALDA And you saw that show, and what did you think to yourself, what was your reaction to that?

JOANNE SAKELARIS I thought it was cool that the guy was going up in that elevator. And I was looking at his eyes and going, oh, he knows, he knows the feeling.

ALAN ALDA (Narration) Joanne Sakelaris, who lives in Seattle, went to her therapist and asked if virtual reality was being used to treat arachnophobia. He contacted a VR researcher at the University of Washington, Hunter Hoffman.

ALAN ALDA You can make it a little tighter.

HUNTER HOFFMAN Oh, OK. That better?

ALAN ALDA Yeah, yeah.

HUNTER HOFFMAN Now, if you hold your hand out, you should be able to see your…

ALAN ALDA I see my hand.

HUNTER HOFFMAN Cyberhand.

ALAN ALDA My cyberhand, OK.

ALAN ALDA (Narration) Within a few weeks, Hunter adapted an existing VR environment into one that's an arachnophobe's nightmare.

HUNTER HOFFMAN If you can just move over toward that vase.

ALAN ALDA There's the vase. Oh my…! There's a spider! What's that spider going to do?

HUNTER HOFFMAN It's unpredictable.

ALAN ALDA I really did react to that little thing wiggling its arms.

HUNTER HOFFMAN What was your anxiety when you first saw it?

ALAN ALDA (Narration) Watching me along with Joanne is her therapist, Al Carlin.

ALAN ALDA From zero to one hundred. Oh, I don't know, about 20 or 30. I mean I had a little startle reaction. I got used to it right away because it's clearly virtual. But there's something about that shape that I have an automatic reaction to.

HUNTER HOFFMAN So try to herd him into that sink.

ALAN ALDA Into the sink?

HUNTER HOFFMAN Yeah. So you just have to bend your knees so you can see him. Yeah there he goes, now push him into the sink. There he goes. Now see those little red and blue buttons just to your left? Touch those and it'll turn the water faucet on. Now touch this apple…

ALAN ALDA Poor guy. Why didn't we just throw him out a window?

AL CARLIN Well, he comes back.

ALAN ALDA Well then forget about it.

HUNTER HOFFMAN Let's take a short break.

ALAN ALDA All right. Well, am I cured now?

AL CARLIN You're the best judge.

ALAN ALDA How will I know if I'm cured?

AL CARLIN We'll find out.

ALAN ALDA You're not going to give me a real spider, are you?

AL CARLIN We'll see what happens.

ALAN ALDA What was it like watching me go through this? Did that bring back the process for you?

JOANNE SAKELARIS Yeah, because my hands got sweaty watching you.

HUNTER HOFFMAN Now that you've achieved some level of desensitization, we move to the next stage.

ALAN ALDA Is the spider going to get worse, is that it?

HUNTER HOFFMAN Can you see OK?

ALAN ALDA (Narration) Now at this point, you know more about what's going on than I do, locked away as I am in my virtual kitchen.

ALAN ALDA What is he, on a thread or something?

HUNTER HOFFMAN He's on a spider web. So what's your anxiety from that spider?

ALAN ALDA I have to tell you that I consciously don't feel a lot of anxiety, but I'm noticing that I feel here in my chest and my stomach, I really feel a physical reaction.

AL CARLIN So just keep looking at it, and if you can, try to take a deep breath, hold it for a moment and breathe out slowly.

ALAN ALDA Where'd he go? Oh, he went someplace, up and down. I don't like it when it gets out of my sight.

HUNTER HOFFMAN If you can just reach out and touch the spider, with an open hand.

ALAN ALDA Open hand. Aah.

HUNTER HOFFMAN Are you OK with that?

ALAN ALDA Yeah, yeah. Ah! You know what just happened? You put that thing in my hand, that controller, but you were holding it right where the spider was. And when I put my hand over there, and there I got that controller, I thought I was touching the spider.

HUNTER HOFFMAN OK, try touching that again.

ALAN ALDA You didn't do that deliberately did you?

HUNTER HOFFMAN Try touching that again.

ALAN ALDA Where is it? Ah…

HUNTER HOFFMAN So did that feel like a spider when you first touched it?

ALAN ALDA Yes of course it did.

HUNTER HOFFMAN So what was your anxiety then?

ALAN ALDA Well, I think my laughter was an expression of my anxiety.

HUNTER HOFFMAN OK.

ALAN ALDA And I didn't know what it was. It was a shock. It must have been 60 or 70. Ah, this is disgusting.

HUNTER HOFFMAN OK.

ALAN ALDA Ah, it's a tarantula, too. It's very interesting. The longer we do this, the more convinced I am that I'm deeply anxious about this, and you're not going to get me out of it.

AL CARLIN I suspect that with time you'd get real comfortable, almost sort of bored with this virtual spider. But hopefully if you're somewhat anxious along the way it may move you to be less destructive to those guys when you meet them in the real world. The may never be your favorite critters…

ALAN ALDA But I can learn to coexist with them.

AL CARLIN You can learn to coexist and I think also to learn to be less troubled by the visceral response you have to them.

ALAN ALDA Is this something you could have done before you had that therapy?

JOANNE SAKELARIS No…

ALAN ALDA (Narration) Since Joanne came up with the idea of VR therapy for arachnophobia, the program has been extended and is now being offered to others.

ALAN ALDA You wouldn't even have been able to look at a field? And here you are walking through it.

JOANNE SAKELARIS I know.

ALAN ALDA And what are you experiencing?

JOANNE SAKELARIS Nothing!

ALAN ALDA Really?

JOANNE SAKELARIS Joy. I can't explain it, it's so… I went camping, and I've never been able to go camping before, and I mean that for me that was… great.

ALAN ALDA (Narration) Not only can Joanne now go camping -- she's even ready for a visit from Rosie.

RICK WEST I understand you had a real fear for tarantulas at one time? And you've overcome that, do you think?

JOANNE SAKELARIS Yeah, I'm confident.

ALAN ALDA (Narration) This is someone, remember, who could spot a tiny spider 50 feet away -- and fly into total, uncontrollable panic.

JOANNE SAKELARIS This is so cool.

RICK WEST Can you feel the little claws on the end of her feet? They're like a cat foot.

ALAN ALDA (Narration) As for me, my mind is filled again with visions of that tarantula I struggled with in the swimming pool as a kid.

JOANNE SAKELARIS This is cool.

ALAN ALDA When it started to crawl up your arm, I was cringing, and I thought, how can she tolerate that? And you're the one who had the problem. And I'm sitting here thinking I'm going to go out of my head if you let that crawl any further up your arm.

ALAN ALDA (Narration) I don't know if it was the VR therapy or just Joanne's bravery, but… here goes.

ALAN ALDA She's got the softest touch, you know.

ALAN ALDA (Narration) And so, having learned in the last hour to appreciate spiders, I finally make contact.

ALAN ALDA Well, my heart's not pounding, too much. I can't breathe, but my heart's not pounding.

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