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S2E05: The World of Giant Touchy Arachnids

This week we imagined what life might be like on a world where the appearance of the night sky changes every year. Get ready for some 8-legged fun!

HOSTED by Dr. Moiya McTier (@GoAstroMo), astrophysicist and folklorist


Dr. Lauren Esposito is an arachnologist and assistant curator at the California Academy of Sciences. Lauren co-founded the conservation non-profit Islands and Seas and the visibility campaign 500 Queer Scientists. The New Science Exhibit about queer and intersectional identities can be found here. You can follow Lauren on twitter at @ArachnologyNerd and instagram at @arachnerds.


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Moiya 0:08

Hello there friends. Welcome to Exolore, the show that helps you imagine other worlds with facts and science. I am your host, Dr. Moiya McTier. I'm an astrophysicist who studied pretty much everything in space from planetary orbits to the radiation leftover from the Big Bang to star formation and black holes and Galaxy evolution. But I am especially interested in the motion of stars and how that affects the habitability of exoplanets, which are planets outside of our solar system. I am also a folklorist who specializes in building and analyzing fictional worlds. And this podcast is my way of sharing those worlds and that knowledge with you. So let's get started.

Moiya 0:52

Thank you so much, Lauren, for being on Exolore. I have been thinking about this world for a very long time. And I have also been thinking for a long time that you're like the perfect person to join me on this episode. So thank you. And in your own words, would you like to tell me and the listeners who you are and what you do?

Lauren 1:12

Sure. I'm Dr. Lauren Esposito, and I'm the curator of arachnology at the California Academy of Sciences. And I guess what that means is that I study arthropods with eight legs, which I think are like the perfect candidate for other planets, to be honest.

Moiya 1:29

Yeah. Why do you think so?

Lauren 1:31

Well, I mean, they were the perfect candidate for ours. Arthropods have been dominating Earth's ecosystems for like 500 million years or so, maybe six? And they've succeeded, exceptionally well. In fact, arthropods on earth today are the greatest concentration of diversity that we see. And so not only have they succeeded in surviving throughout all this time, [but also] during a period of time in which Earth has gone through considerable change, but they've thrived in those circumstances.

Moiya 2:04

Yeah, the fact that I can see spiders in my Manhattan apartment, proves that they can exist in any environment.

Lauren 2:12

Yeah. If you think about anywhere, they're probably there.

Moiya 2:15

So how did you get to studying arthropods, and things with eight legs? No more, no less.

Lauren 2:21

No more, no less. Well, sometimes they have less, but mostly they have eight. I always wish I had some story about how I always knew I wanted to be an entomologist, or an arachnologist and some, like, amazing description of a path that seemed inevitable and when I think back about it, some parts of it, maybe were inevitable, but I mean, I guess I really started in earnest. When I was an undergraduate going to the University of Texas at El Paso, I was like a pretty young college student, because I'd hated High School. And I like hated high school so much that I was either going to drop out or graduate early, and I graduated early and enrolled in the University of Texas at El Paso, nowadays, it's probably more competitive. But at that point in time, it was more like a community college where you could just enroll.

Moiya 2:21

Got it. I love that you're like, "I hate high school, Let me do harder high school".

Lauren 3:15

Well, I actually didn't want to, what I wanted to do when I graduated high school at the age of 16 was get in this old Toyota pickup truck that I had, and like drive around the country and go like camping and national parks. But my mom, who at that point, still had a decision and what I did with my life, because I was 16, was like, "Yeah, I don't think that's a really good idea for my 16 year old daughter to go drive around the country with no job and no money and no security." I mean, you don't get that kind of a scary thing to be like, "yes, 16 year old daughter, like go see the world." So she was like, "I think that you should go to college." And so I enrolled in the local college. I think actually, my mom sort of like enrolled me.

Moiya 3:56

Oh, the power of motherhood.

Lauren 3:57

I know. I mean, my mom is fantastic, so I don't hold it against her. In fact, I guess I have her to think for all of this. I was a biology major, I'd always loved science in school. I loved my biology classes in particular, I think because I had some really great science teachers who encouraged me along that path, but also because both of my parents are biologists. My dad is a veterinarian. My mom went to school for wildlife biology, but mostly worked in my dad's veterinary clinic when I was a kid. And so I grew up with all of it. I'd just been surrounded by it, and I knew I didn't want to be a vet like that much was clear. But what I wanted to do as a biologist, I didn't know and I didn't really have a good sense of what the career options out there were, so I was pre med, because I feel like a lot of biology students are like, "what all do you want to do? I want to make money so I'll be a doctor."

Moiya 4:47

It's a good default. Yeah,

Lauren 4:49

Yeah. And I actually hated being pre med. I didn't really love the classes I was taking like, they were challenging, but not fun. Like all the classes that everybody takes, if you're a science major [are] like Intro Bio and Intro Chemistry and Physics and all those things. They were fine, but I wasn't like, "Ah, this is what I want to do." And it wasn't really until I took entomology class that I was like, "Oh, this is actually really fun!" Because a lot of the class was going out into nature and looking for insects and observing them and collecting them and studying them under microscopes. I love that. And I will say that I still hadn't at that point, but like, "Yes, I want to be an entomologist." I was still pre med and still doing all this stuff. And then the next class I took was one that was mostly motivated because in the course description said that the course was going to Baja, California, Mexico, and spending a week on a beach for Spring Break. And I was like, "yeah, I want to take this class. Of course, that's a no brainer, like Mexico for spring break for school?"

Moiya 5:53

Yeah. Sign me up.

Lauren 5:56

So I did, I took that class. And by the end of that class, I was like, "No, actually, what I really love is field biology and like going out in nature and doing studies," and one of the great things about that class was we had to come up with an idea for an experiment or some sort of study to do out on this beach. And then go and do it during Spring Break. It wasn't just Spring Break on the beach, it was like hard work Spring Break on the beach, but fun.

Moiya 6:21

It was school.

Lauren 6:21

Yeah, it was school and and so I came up with this question that I wanted to answer about whether Fiddler Crabs, you know, this little crabs on the beach that have one big arm?

Moiya 6:31


Lauren 6:32

You've never seen those?

Moiya 6:33

I can imagine it.

Lauren 6:34

Nature channel or something. So they're like little crabs, they live on the intertidal zone of the beach, they dig holes in the sand. And the male crabs have like one major arm and one little tiny minor arm.

Moiya 6:45

Is it the same arm all the time?

Lauren 6:48

That's what I wanted to know, look, great minds think alike.

Moiya 6:51

Look at that.

Lauren 6:51

So I was like, "are they right handed or left handed?" And I like looked through the scientific literature to try to answer this question and couldn't find an answer. So I was like, "that's what my projects gonna be. I'm gonna go to the beach. I'm gonna spend all day on the beach digging up Fiddler Crabs out of the sand and counting how many were right handed and how many were left handed." That's the project I did. The answer was it's like 50-50.

Moiya 7:12


Lauren 7:13

But nobody had ever published any scientific paper on that. And I found that really fascinating that there was like still unknowns as like, relatively simple as that whether Fiddler Crabs were mostly right or left. And that kind of like blew my mind. And since then, I've just made a series of some ways they were missteps, but most, but they all worked out. And in the end, I became an arachnologist.

Moiya 7:36

That's really awesome. Have you ever taken that trip around the country in your truck?

Lauren 7:41

No. But now I get to travel the world, not always on a truck. But usually there's a truck involved.

Moiya 7:47

Good to carry all the equipment.

Lauren 7:49

Yeah, to carry all the equipment and to get to the places that are hard to get to? Because those are the places that still contain a lot of the unknowns.

Moiya 7:56

Where are the coolest places you've been?

Lauren 7:58

Oh, coolest. I mean, that's so hard. Because every place I go to is so cool.

Moiya 8:03

That's a nice diplomatic answer.

Lauren 8:04

No, I mean, it's diplomatic. But I also like I love traveling, I love seeing new places. And so it's not very hard to impress me, I have like a low bar. But I would say one of the most like mind blowingly amazing places I've ever been is this island nation off the coast of West Africa, called Sao Tome and Principe. And it's a small island archipelago of, I think there's five islands, but really just two major islands where people live. And it is like out there in the middle of the ocean. And like the animals that live on these islands are really weird, because they somehow randomly got to these islands that were uninhabited and made their way you know, and were able to survive, and it's a really cool, very special place.

Moiya 8:47

That's awesome. Okay, so to change tracks a little bit to get into the fictional world theme of the show. I always ask my guests what fictional worlds you've been inhabiting lately, whether that's books, movies, video games, whatever. So where have you been in your mind?

Lauren 9:06

Ah, man, that's such a good question. I mean, I read a lot of books and like mostly the sorts of books that I read our science fiction worldbuilding kind of books that are like fast reads. I like youth sort of novels.

Moiya 9:21

Like YA stuff?

Lauren 9:22

Yeah, like young adult because I really like book[s] that I can [read],and I'm done with it in like six hours and ready to move on to the next one.

Moiya 9:29

Oh, you don't get that like post-book ennui where you can't go into another world for a while?

Lauren 9:34

I don't, I can just read them back to back but oftentimes, [I] have phases of reading so I'll be on a field trip and have budget downtime to read. And I'll like power through like three books and just be like completely absorbed in them. Maybe it's like a rainy afternoon on a tropical island, and I can't go out and work so I just want to read a whole book. And then I don't wanna have to remember where I left off because that's my biggest problem, once I stop reading [it's] like I can't remember what happened. And then after we read the whole book, and it's very frustrating.

Moiya 10:06

So short books. What have you read lately? Do you remember any titles?

Lauren 10:12

Oh, man, I'm reading a book right now. And I can't even remember what it's called.

Moiya 10:15

What's it about?

Lauren 10:16

It's about a world where there's a wall, and on one side of the wall magic happens. And on the other side of the wall is just like normal humans. I wish I was more prepared, but it's great. I love the book.

Moiya 10:28

That's okay, I sprung this question on you.

Lauren 10:31

But it's really cool because like, on both sides, people are sort of aware of the other side, but there's not really like a lot of crossover.

Moiya 10:39


Lauren 10:40

And on the side where magic happens, like, that's very normal, and matter-of-fact, and on the other side, like people are like, "What? No, that can't really be real."

Moiya 10:48

Which side would you want to live on?

Lauren 10:49

Well, the magic side seems kind of terrifying because there's a lot of people rising up from the dead.

Moiya 10:55

Don't like that.

Lauren 10:56

Yeah, that sounds frightening. I mean, I feel like I'd like to live kinda in the almost border zone on the normal side. Because then like, once in a while, something really cool magic[wise] happens, but like, not usually something devastating, like a whole army of dead rising.

Moiya 11:11

Yes. Good to avoid that. Keep a wall between you and the undead army.

Lauren 11:16

Yes, exactly.

Moiya 11:17

At least one wall.

Lauren 11:18


Moiya 11:19

Cool. Well, are you ready to build our own fictional world?

Lauren 11:23

I think so.

Moiya 11:23

Yes. I'm really excited about this one.

Lauren 11:25

I was kind of nervous to be honest. I feel like most of the time, I just get asked facts and this time, I get to be creative.

Moiya 11:32


Lauren 11:32

It made me feel nervous.

Moiya 11:34

Oh, I still get nervous, if that helps you. But hopefully, by the end of this, you'll have had a great time.

Lauren 11:40

No, I'm excited.

Moiya 11:41

Okay, good. So the world we're building today is one where there's an ever changing night sky. So from the time that it takes the planet, this world to get from like the same part in its orbit, make a whole orbit over a year and then get back to the same point, the constellations in the sky have changed. That also happens from season to season, the constellations are changing, but that happens here on Earth, too. So the important thing is that the constellations are changing every year in this pretty unpredictable way. And the way that you can get that to happen is if your planet is in a dense stellar environment, like a globular cluster, which are these clusters of stars, anywhere between 10 and a few 100 light years across, and they can have like 10s or 1000s of stars in them. For reference, the part of the galaxy that we're in there are maybe like a couple of stars within 10 light years. So it's much denser than our part of the galaxy, there's more radiation there because stars are giving off radiation. So high amounts of X rays, UV rays, and Gamma rays. And a lot of these stars in the globular clusters are going to be much older than our Sun. So our Sun is about four and a half billion years old. Most of these globular clusters we think are probably remnants of old galaxies that have merged with the Milky Way. So they have older stars. So let's imagine that the average age of a star in this globular cluster is about twice as old as our Sun. So these stars are 10 billion years old, the planets themselves are going to be really old. So I'm thinking like, maybe time for lots of mass extinction events in the past on this world? We can play with that as we will, but but that's what we're working with. So do you have any first reactions to any of that?

Lauren 13:21

I mean, I think [my] first reaction and of course, my thoughts are always biased towards arthropods, which [works because] arthropods are perfect for this because they like would be able to effectively deal with high levels of radiation, high levels of UV and in particular because they have exoskeletons that help them to deal with that; they have armor on the outside. My second thought is like when you talk about an old world, one thing that comes to mind for me is really sort of decomposed rock, so like imagine that the world is probably kind of like cooled down a little bit where there's not active magnaflow if there ever was and that the rock is like cooled and had lots of times to erode, and so it's like this kind of crumbly landscape that's what pops into my brain so those are my initial thoughts.

Moiya 14:09

I love that already. The exoskeleton is that made of the same type of stuff is our skeleton like all the calcium and whatever else is in bones?

Lauren 14:19

Yeah, so it's more like hair or fingernails, it's made out of a material called chitin. So not the same as our skeleton, it also forms simultaneously around the entire organism. So take the example of a spider, spiders when they molt their exoskeleton, which they have to do in order to grow because it constrains their size, they molted and their whole entire body all their skeleton comes off all at once simultaneously, but also so does their entire digestive system and the reproductive organs and like everything else is just all comes off. So they start over again, periodically. So if it were to get damaged because of high radiation, or UV, then like suddenly they have like a whole new digestive system and like new coverings on their lungs and everything, all of it.

Moiya 15:07

Yeah, you're right. They are perfect for this environment. So besides the exoskeletons, what other physical or biological traits do we think would do really well in this environment?

Lauren 15:17

I mean, I guess when you say the stars are much older, they're probably giving off considerably less light. Is that true or not true?

Moiya 15:25

Less visible light, but they're still giving off light, and other parts of the electromagnetic spectrum. Yeah.

Lauren 15:31

So I mean, I guess like thinking too, about, like, how much gas would be present in the atmosphere, I'm thinking about maybe things that are able to deal with relatively low levels of whatever gas they need, like, presumably oxygen, because that's the way that we interpret most living organisms on earth is the need for oxygen or carbon dioxide. So probably like lower than we're used to here on Earth, levels of those gases

Moiya 15:55

Oh, especially like you said earlier, if there's not much geological activity happening inside, like, if the planet itself is kind of cold and dead in a way, then there won't be the carbon cycle that can get a lot of the carbon dioxide out of the air. So I'm thinking higher rates of that.

Lauren 16:12

That's absolutely true. So it may be that the autotrophs or things that are like using raw energy from the sun to create other forms of energy have to be using some alternative, like mechanism other than the way that plants do here on Earth. Like, I'm thinking more like deep sea events.

Moiya 16:30

Like a chemosynthesis.

Lauren 16:32

Yeah, some kind of chemosynthesis, and those autotrophs, I feel like they're gonna be the cornerstone of whatever the the food web is. But they don't actually matter that much. Because they'll always be something that's really successful at taking raw energy and converting it. That's going to be like the basis of any ecosystem anywhere, no matter what the makeup of that planet is.

Moiya 16:53

That's a good point. So maybe let's focus our conversation on what we think would be at the top of that food chain.

Lauren 17:00

Right, which is why I'm here. I'm here to talk about the predators.

Moiya 17:03

Yes, you are.

Lauren 17:04

Things that come to mind for me right away that I think make arachnids really probable and like arachnids for the record have been featured in Sci-Fi worlds as being like the top thing.

Moiya 17:15

Oh, okay. They're beating out crustaceans?

Lauren 17:19

Although I feel like sometimes the representation to be honest, is like sort of a hybrid between crustacean and arachnid, which is fine, fine by me, they do share a lot of similarities. But arachnids, like scorpions have the lowest metabolic rate of any animal on earth.

Moiya 17:33

Is that good?

Lauren 17:35

That's great, because then they can like survive. If there's like periods where I don't know like there's decreased solar activity or something, they can survive those hurdles [with] decreased metabolisms so they don't need as much oxygen and they don't need as much food and whatever water kind of liquid things they would use.

Moiya 17:54

That's really nice, but I imagine they're also probably not very active during that time. Is it a hibernation almost?

Lauren 18:00

It's not really hibernation, they're still fully active. They just have really low metabolisms. Like, they don't need a lot to get by.

Moiya 18:06

Oh, wait, that's really cool. They don't need a lot of resources from outside, but it doesn't necessarily affect their day to day behavior as much?

Lauren 18:14

No, yeah. Like, they may be like a little less active than normal, but they'll probably still have like, more or less normal activity levels.

Moiya 18:22

That's really great. That'd be useful here. So what do we think they look like? What are you imagining in your head?

Lauren 18:29

Well, I think about the history of arthropods on earth; and historically, they were really big, but they were really big because I was really high oxygen concentration levels on earth. And so in this scenario, if there's lower oxygen concentration levels, and they probably are really small, rather than really big, which is kind of a bummer, because I would like them to be like, gigantic.

Moiya 18:50

Why does the amount of oxygen effect size?

Lauren 18:53

Because they passively respire. So instead of having lungs that breathe in and out, they have more like gills structures? Actually, they are internalized gills that oxygen just diffuses over. And so the concentration of oxygen in the air limits their size, because they're limited by the rate that they can absorb oxygen and get it in all their tissues.

Moiya 19:13

Got it. So if there are some of these creatures, these life forms that are near sources of a lot of oxygen, then they can get bigger?

Lauren 19:22


Moiya 19:23

Is it like on the individual scale? Or does it happen more over time?

Lauren 19:28

It happens more over time, which may be reflected on the individual scale and that like the larger ones, are able to have more offspring. but are only able to survive if they have access to higher oxygen concentrations. So like over time, larger sizes get selected for instead of against.

Moiya 19:45

Got it. So I would love the idea of the species, being able to tell where someone else is from based on how big they are. Like if there are families that are from different parts of this planet and some parts are like maybe in a forest where there's going to be more oxygen. They can get bigger.

Lauren 20:01

Well, here's the thought, what if in this world because it's a crumbly world, and it's had lots of time for erosion, there's like big cave systems underground. And those cave systems could like harbor greater levels of oxygen from like back in time when there was more oxygen on that planet. And so cities are built around caves that have higher oxygen levels. And so they're also kind of like restricted to those caves because there's a urban growth constraint where the cities can't grow any larger because they have to stay in their own cave system. And the next city is like the next cave system over.

Moiya 20:34

I love that a lot. I really do. Do we think given this planet's long history that the - should I call them arthropods?

Lauren 20:44

Call them call them arachnids.

Moiya 20:45

Arachnids. Okay. Do we think these arachnids have always been the most powerful species on this world?

Lauren 20:55

If we take a page from the book of Earth, we can say that they had their moment as like the top predators of the ocean. And then when everything moved on to land, in this case, eventually the oceans in this world dried up,maybe? It's an old world, there's not so many oceans. Then during their time on land, they would have gotten smaller. Because also the other thing about the ocean is that it removes like gravity limits. So body size can be larger because there's not as much gravitational restrictions about how to move and how big you can be.

Moiya 21:27

There's buoyancy in the water.

Lauren 21:29

But then they came on land, and they got smaller on land and oxygen levels went down. And eventually they found the caves, which is the thing that actually happens, like we know that that happens on Earth, like caves are oftentimes rifugio during a global change events. So like things find their way into caves. Maybe there's like a glacier covering up the forest that they used to live in. And then when that glacier recedes again, things come back out of caves and reoccupy the forest as it grows back. So if they found their way into caves as like, the oceans were drying up, and they were looking for, like moisture, and oxygen rich pockets, everything else may have died off. And since that time, they've returned back to the rightful place as top predators.

Moiya 22:11

Yeah, I like that a lot.

Lauren 22:14

But they had to live in fear for a while, like that intervening time between ocean and cave. They were you know, they weren't [at] the top.

Moiya 22:20

It'll build character for the species. How long do we want them to live? Do we want them to have long or short lifespans? Do you think?

Lauren 22:29

I feel like something intermediate, like a 25-50 year lifespan.

Moiya 22:34


Lauren 22:35

Is that long?

Moiya 22:36

Is that long for a scorpion here on Earth?

Lauren 22:38

A Scorpion on Earth can live somewhere between 7-25 years.

Moiya 22:44

Okay. One of the advantages, I think of having a long lifespan is that an individual person can contribute more before they die. So I think that that makes it easier for the species as a whole to advance more quickly. So I see that as a proxy for how quickly can this species advance. So if we're thinking intermediate lifespans, then intermediate rate of advancement.

Lauren 23:09

True, but I wonder to what extent [how quickly] you become an adult factors into that. If you have an intermediate lifespan, but reach maturity at human rates, you only live 50 years, [hence] you're not mature until [about] 18. But if you reach adulthood by 3, then that's a whole different scenario like that maybe makes your life comparatively longer.

Moiya 23:39

I hadn't even considered that, that's a really great point. So reaching maturity around 3, is that typical?

Lauren 23:44

Yeah, I would say that somewhere between 1-3 for scorpions, that's about right for spiders, like within a few months, in many cases, and then others, like sort of 1-3 year timespan.

Moiya 23:56

How related are spiders and scorpions?

Lauren 23:59

They're not each other's closest relative, but they're part of a group that is all each other's closest relatives. So there [are] two other things that are missing from [this] conversation, and they're groups of arachnids that nobody really has ever heard of. So for all intents and purposes, they're basically each other's closest living relative.

Moiya 24:17

Okay, what's left?

Lauren 24:19

The other two are a group called Whip Spiders or Amblypygis. They kind of look like a crab. They actually are one of the most cave adapted groups. They have six pairs of walking legs and two legs that are like these long, crazy antennae that they use to like feel around. Most spiders and scorpions have venom, but these guys don't have venom. And then the other group is Pseudoscorpions, which look kind of like a scorpion, but doesn't have a tail and it's really tiny.

Moiya 24:49

Do you want our creatures to have tails?

Lauren 24:51

I feel like I kind of like the spider body vibe, more like tarantula-style. They're just so cute. When you look at them, they just [look] like fuzzy little puppies. I can just imagine a whole species walking around talking and looking like little puppies.

Moiya 25:08

Little eight legged puppies. Do our creatures have webs? Or can they make webs?

Lauren 25:16

I mean, I feel like it's an advanced society and so they can make webs, but they don't make them for like living in they like use their silk for like specific purposes, like making baskets or building like advanced architecture.

Moiya 25:32

Do you think they have competitions to see who can build the most like intricate web designs in the caves?

Lauren 25:38

Yeah, probably.

Moiya 25:39

Yeah. Okay. I like to think about that, too.

Lauren 25:42

And they make little hammocks to lay in.

Moiya 25:45

I'm imagining a very chilled species now.

Lauren 25:48

And the old ones just sit at home and like knit afghans.

Moiya 25:54

Right, because it's so cold on this planet.

Lauren 25:56

It's cold, and they live in these caves. But although maybe the caves are like a little warmer than everywhere else, because they're like closer to the core, they're like deep caves.

Moiya 26:09

Oh, I love the idea of there being this like ritual. If you know that someone's about to leave the cave. They have to make their own blanket or like maybe if a loved one makes one for them.

Lauren 26:19

Yeah, they get a blanket to take with them. Or a cape -it's like a hood. And they have to put it on the stay warm.

Moiya 26:27

Like Little Red Riding Hood, but it's a tarantula, walking out of the caves. That's awesome. All right, I think it's time for a break. And when we come back, we're going to talk about more of the social cultural aspects of this arachnid life form.

Moiya 26:44

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Moiya 28:36

Welcome back. I am really interested in how arachnids socialize with each other and how that would translate into this world? Is it the same over all arachnid species that you've studied or does it vary?

Lauren 28:48

So they're super variable and their levels of sociality ranging from arachnids that basically only ever interact for mating, all the way up to sort of sub social groups that live cooperatively. In fact, there's even spiders that cooperatively hunt.

Moiya 29:06

What do they hunt?

Lauren 29:07

Well, they build their webs together. And then flying insects will fly into the web. And because the spiders are really tiny, but collectively, their web is really big. They can capture insects that are much larger than they would be able to capture individually. And then they like, eat them, like all together. Like just a bunch of spiders eating this thing.

Moiya 29:30

It's like a big spider banquet.

Lauren 29:32

It is like a spider banquet of tiny spiders.

Moiya 29:37

Since its variable, you can pull from all of the different species, just the parts that you like. How do we want our arachnid species to socialize?

Lauren 29:46

Well, I really love a couple of different arachnids. For one, I'm going to draw from the Whip spiders. They're actually very cute, and all spiders exhibit some level of maternal care. So basically all spiders either way, they guard the eggs till the eggs hatch or, in some cases they like care for the young long after the eggs hatching, and Amblypygis are included in this and they lay their eggs in like an egg case that they glue to their stomach, and then when the babies hatch from the eggs, the babies crawl up onto the mom's back and she like wears them like a little backpack for a little while. And then after they're like a little bigger, they move off of her back and they just hang out like around her. And remember I mentioned they have like one pair of legs, that's these long, curly whips that they use for feeling around. Imagine antennae, like they're these long antennae and the mom and the babies will all reach out and like stroke each other with these antennae and the antennae are like covered and all kinds of sensory things. So they can like pick up pheromones, so kind of like smelling and sensory so they can feel like vibrations and she'll like reach in and like stroke the babies and the baby stroke each other and they stroke them mom. And so they're like very tacitly involved, and I think it's like very adorable.

Moiya 31:05

[That's] cute as fuck.

Lauren 31:06

Scorpions also exhibit the same kind of thing where the babies crawl up on the back of the mom. But what's different in scorpions versus all other arachnids is that the moms actually give birth to live babies. So they're live bearing arachnids, and they have like an over uterine systems. They received this like direct nutrition from the moms uterus like the same as humans, where we have like a placenta and you get nutrients through the placenta.

Moiya 31:33

How many babies are we talking on average?

Lauren 31:37

Anywhere in the range of 2-100s. I feel like this arachnid society shouldn't have hundreds of babies, because that just seems weird and like unsustainable for cave living.

Moiya 31:51

Right because the population has to be pretty limited unless they're sending people out lottery style.

Lauren 31:58

I know, but that's awful.

Moiya 32:00

Yeah, that's awful.

Lauren 32:01

Like to just die with their afghans up on the surface.

Moiya 32:05

Oh, I was hoping that they could still survive on the surface, they just wouldn't have the easy city life that the cave arachnids have.

Lauren 32:13

There'd be like Queen Bees down there just having the babies and then everyone else would like go fend for themselves up on the surface.

Moiya 32:20

Maybe, we could make it like that - we don't have to make it this terrible. But if the population does get too big, maybe they draw lots to see who has to leave. Or maybe if they're a very honorable like noble people, maybe people will volunteer to leave. Maybe there's a legend of some lost distant city and people like choose to go and find it.

Lauren 32:49

Arachnids are also really good excavators and they're good at digging burrows. So maybe they are able to expand their cave system and like keep burrowing into it to develop new cities. This actually happens in cave system living arachnids, where the caves are all connected genetically. So even though like humans can't see how these caves could possibly be connected, like clearly there's like little microscopic passages or something that the spiders are getting through. And so maybe these spiders also do the same thing where there's like passages, but it's like a hard, arduous journey to get through those passages and out to the next cave system. And so maybe they're expanding into these caves and excavating them.

Moiya 33:36

Yeah, maybe they can use their webs to like add structural integrity to the caves as they expand and build new ones.

Lauren 33:45

Well, their webs are super strong. Spider silk, like some spider silk, like dragline silk, which is what they use to make the long lines of their web that attach to the plants. If you've ever seen like a "Charlotte's Web" style spiral web, you know, there's like anchors that anchor it into place, and then there's the spiral in the middle.

Moiya 34:02

And it's a different type of silk?

Lauren 34:03

Yeah, they make multiple different types of silk and the dragline silk that's anchoring silk is stronger than steel.

Moiya 34:12

Great for architecture.

Lauren 34:14

Yeah. It's stronger than steel. And it's more tensile than Kevlar, so it can absorb tremendous amounts of energy.

Moiya 34:23

If they do have a standing army, they're just so protected.

Lauren 34:26

Yeah. Forget it, nobody's getting in those caves if they don't want them there.

Moiya 34:30

Yeah. All right. So you said that you wanted to draw from three different arachnids: the the whip spiders, the scorpions and their live births. And what was the third?

Lauren 34:40

The third actually also comes from scorpions, which is that some scorpions live these sort of sub-social lives where they build boroughs, they construct borough systems and the borough systems can be really really deep and have chambers and oftentimes, and they're really long lived species within one borough system, you'll find like different ages, different age structures, meaning like there's a mother scorpion that constructed the borough, and within her borough are like different ages of her children still living within the borough. So they're not necessarily like interacting socially or like hunting together, but they're like cohabitating and so it's like kind of like an apartment complex for like multigenerational apartment building.

Moiya 34:46


Lauren 34:56

And so I feel like these arachnids could be living in this multigenerational sections of the cave where there's like, the granny, but then like, in the apartment downstairs is like some of her offspring and some of their offspring and other compartments.

Moiya 35:42

Do you think there's any sort of positional hierarchy here?

Lauren 35:49

I feel like the youngsters have to go up top.

Moiya 35:52

Yeah, they have to do all that work.

Lauren 35:54

Yeah, cuz also if it's still a little warm down at the bottom of the cave, like the depths of the cave get the greatest heat still from the core of the planet, and the higher up you get in the cave, the colder it is.

Moiya 36:06

I like that. What are the dads doing? You haven't said anything about [them].

Lauren 36:10

Well, it depends. Like some spiders, the the male will live with the female spider. And actually, there's like some kind of interesting stuff that happens. So in spiders, we see this phenomenon of female gigantism. In some species, the females are like 20-30 times the body size of the males. And the females build these like massive webs. And they live in their web, like, you know, like Charlotte. And the male will find a female who doesn't have a male living in her web yet, and he'll like move himself in.

Moiya 36:11

Just freeloading.

Lauren 36:17

He's freeloading, but like to be honest, he's also like cleaning up all the gnats that she doesn't want to eat because she can't be bothered eating those little gnats, [that are] getting stuck in her web. And what he does his entire life as he defends her web territory from other males, he keeps out other spiders from her web. And they do really weird stuff. Spiders have the weirdest sex, honestly, it's just bizarre,

Moiya 37:06

I want to hear all about it, please.

Lauren 37:08

So in addition to mate guarding, they do all kinds of weird stuff in many ways as a result of this differential size. All arachnids exhibit varying levels of courtship, where the male courts the female, usually using a combination of acoustic signaling and visual signaling. So he like plays music and does a dance, in some cases.

Moiya 37:36

That'll be great in the caves.

Lauren 37:37


Moiya 37:38

Great acoustics.

Lauren 37:39

Really good acoustics at the entrance of each of those little houses, in the wall, and all of that acoustic signaling is meant to be sort of a signal of his fitness. And so in many cases, the songs and dance require a lot of energy to perform properly. And that like demonstration of energy use is supposed to signal to the potential mate that like he's doing all right, like he's getting all the food he needs. And he's big enough and strong enough to do all this dancing. He's an attractive candidate. But female spiders can store sperm and so they can mate with multiple spiders. And then somehow, in this chambered, sperm storage can ultimately choose which sperm to use to fertilize their offspring. So they're kind of like, "show me what you got." And then in the end, they're like, "Yeah, suitor number two was the was the fittest of them all."

Moiya 38:34

I'm thinking of this as an audition. How many suitors would they go through before they make the decision?

Lauren 38:39

In some cases, it depends on the conditions because one of the advantages of storing sperm is that you can wait out poor conditions. Say it's the beginning of sort of the wet season, which is typically when spiders become really active, because there's lots of food, there may be a lot of action happening, like lots of males out courting, and the females might mate with two or three of them. But then, like, let's say a big hurricane blows through and suddenly, like there's no more food or trees or anything else, and they can just wait it out until things get better. So you know, it could be one and it could be like five, depending how many years it takes before they lay eggs or have babies. They do other weird things to like, there's some spiders that exhibit this kind of like bondage where the the male spider will like run up to the female and like play a little song and then start wrapping her up with silk, and she just kind of like, goes catatonic and like puts her legs back and lets herself be draped in silk. And then eventually like they mate and then she stands up because she's not actually trapped in any way.

Moiya 39:43

Because she's so much bigger and stronger.

Lauren 39:45

Yeah, she's bigger and stronger and it's not like tightly binding. It's just sort of like laying silk on top of her.

Moiya 39:50

Do you know why?

Lauren 39:52

It does take her a second to break out of the silk and they will cannibalize their mates if given the opportunity. So it's probably just kind of like an extra level of safety for the male, but how it developed in the first place. And the males have all sorts of weird adaptations to like get around this female male like tension. Like in some species, the males present gifts to the female so they like catch a fly and wrap it up in silk, and give it to her.

Moiya 40:22

I love the idea of a fly wrapped up as a gift.

Lauren 40:25

Yeah, like a little present. The funny thing is, like scientists have taken away these gifts from the males as they present them, and unwrapped them to see like what the actual value of the nutrition was. And sometimes they're not very honest. And they like will wrap up an old like fly carcass they already ate and bring it to her like it's a present or like a leaf or a rock.

Moiya 40:46

Oh, that's sneaky.

Lauren 40:47

Yeah. So there's some sneaky ones.

Moiya 40:48

All right.

Lauren 40:49

I mean, there's so many weird bizarre things are some species that have gotten to this point where the female no longer has an external opening to her ovaries. So she has no way to lay eggs. And in the courtship, the male has to like cut a hole in her exoskeleton.

Moiya 41:05

And pull out the eggs?

Lauren 41:07

No, he just cuts a hole and then he like, fertilizes her. And then when she's ready to lay eggs, like now she has a hole to lay eggs through. It's very bizarre, like spiders are just really, really weird.

Moiya 41:18


Lauren 41:20

But you know, the silk actually made me think of something else about like how these houses might be arranged, which is one of the things about spider silk is that the females lay pheromones down on the silk as one way of communicating species. So that if a male approaches a female's web you can like smell to identify whether it's the right species or not.

Moiya 41:39

Oh, smart.

Lauren 41:40

And so like I was thinking like that families, maybe you could each have their own like custom pheromone scented silk that is all the bridges and stuff between their little chambers of their apartment building, and the staircases. And so then they'd know if they're at the right house or not.

Moiya 41:58

Is their eyesight really bad?

Lauren 41:59

Some spiders have pretty decent eyesight, but they rely on a variety of sensory to interpret the world.

Moiya 42:05

I like this for a couple of reasons. One, they're in caves, it's gonna be dark. Two, even on the surface, there's probably not going to be that much light anyway, if there are these really old stars there. And three, I love my sense of smell. If I could identify things by smell alone, I would choose that, that sounds great.

Lauren 42:23

Yeah, it seems awesome, and I imagine the spiders that live like during the day that have better eyesight, probably use that sense of smell less than the ones that are active at night and don't have good eyesight.

Moiya 42:37

So you said earlier that all arachnids molt? What do we think this life form - if they get to the point of sentient or very advanced or aware of what's going on; what would they do with those moltings? Do we think they'd be proud of them and display them? Do we think that they would like to dispose of them immediately in shame? Like, how do they feel about them?

Lauren 43:05

I don't know. I feel like it could really go either way. On the one hand, I imagine that y'know how people dip their little babies like shoes in gold or whatever?

Moiya 43:14

I've never heard of that. No.

Lauren 43:15

You've never heard of that? Maybe it's a thing from olden times, and I'm old. But like people sometimes or maybe it's like a Texas thing because this is something I remember from growing up. People like take their baby's booties and they dip them in like, I don't know, some kind of like gold or metal or something and like cast them and then they like put them up on their mantle of their fireplace and keep their baby's booties up there forever.

Moiya 43:39

Haha "Look how small your feet used to be!"

Lauren 43:42

Yeah, exactly. And so I feel like on the one hand, like they could get down with something like that, like, keeping these exoskeletons forever. But on the other hand, like, it's a very sensitive moment for spiders and scorpions. I imagine it would be really embarrassing because you're like, suddenly like molting your genitalia. And you're like lungs.

Moiya 44:05

Yes, that sounds pretty vulnerable.

Lauren 44:07

And when they like crawl out of it, it like looks so gross. And they're like, soft, gooey, little things. And then they have to just sit there and wait for their new one to reharden.

Moiya 44:16

How long does that take?

Lauren 44:17

It can take like 24 hours, okay, and they're like very vulnerable. So I feel like they probably have like special molting chambers. And there's like a ritual and you have to go into the molting chamber; and then when you come out of the molting chamber, there's like a party like your birthday party, your molt party.

Moiya 44:34

Molt Day.

Lauren 44:35

Yeah, Molt Day. And then somebody special that works in the molting chambers leads you to the molting chamber and there's like candles all around and then you do your molt, and then you leave and they like dispose of your exoskeleton secretly. Nobody ever talks about it again.

Moiya 44:55

I like that, and it's all anonymous, so no one knows who you are and you don't know have to worry about people making fun of your old genitalia.

Lauren 45:04

Yeah, they're like "oh, look at your genitalia."

Moiya 45:06

I hope no one ever says that to me.

Lauren 45:09

But you know the spider molt spa ladies are like, "Did you just see his genitalia when you took his molt out?" And then they're all laughing.

Moiya 45:16

Absolutely like how I'm always terrified that my gynecologist is like talking to other gynecologist about me, that's what the molt operators are.

Lauren 45:24

I mean, surely they do talk to each other. That's just kind of weird if they didn't, but like, I feel like that's exactly what these molt ladies would do. They don't have to be ladies, they can be molt men. I feel like that's appropriate.

Moiya 45:38

When you were describing what the males do earlier, it did seem like they do the tidying up.

Lauren 45:43

They should do the tidying up. So they're definitely also maintaining the spas.

Moiya 45:48

Nice. What other consequences do we think there would be of this world having an ever changing night sky? Maybe something about navigation because I had heard before that scorpions navigate by the stars?

Lauren 46:02

Yeah, I was thinking exactly that. And I was like, well, okay, if there's these arachnids, and they navigate by the stars to get to other caves, what happens if the stars are never the same? And how are they ever going to find the other caves with the other civilizations in them?

Moiya 46:14

Yeah, what are they doing?

Lauren 46:16

I don't know. I mean, I wonder if there's like, constant wind currents or something that they can like follow the directionality of the wind current because they have these really sensitive hairs on their body that are innervated like cat whiskers.

Moiya 46:29


Lauren 46:30

Innervated. Yeah, they have a nerve connected to the bottom of the hair. Like if you've ever seen a cat whisker it has like that deep socket and their whiskers are super sensitive. They have hairs like that, but all over their whole body so they can sense directionality of wind blowing. So if there's like a constant directionality of the wind, like I'm kind of thinking like our circumglobal trade winds. Then they could follow the wind, head on until till you reach this place, and then you make a left. That's how you get to the other cave system. That was one idea I had, because I feel like the stars are out.

Moiya 47:12

I was wondering if maybe there would be arachnid people whose job was to monitor and like, very quickly record what the constellations are every season?

Lauren 47:23

I wonder how they record it. Maybe they can make a web.

Moiya 47:27

Oh, a whole writing system based on webs. I would love that. Like how there used to be writing systems based on knots.

Lauren 47:35

Yeah, exactly. And they also have glue, so they can lay down glue droplets on to the web, that would maybe like facilitate the writing.

Moiya 47:46

This is the first I've ever heard of spider glue.

Lauren 47:49

Yeah, they have glue. That's one of the reasons why webs are sticky. It's not the silk so much as the glue.

Moiya 47:54

Do they have to apply it separately? Like they make the silk and then they put the glue on it?

Lauren 47:58

Yeah, they have a nozzle. They've got lots of nozzles and one of the nozzles is glue.

Moiya 48:02

What are the other nozzles?

Lauren 48:03

There different kinds of silk. Male spiders even have like a sperm web where they deposit their sperm.

Moiya 48:11

As a web?

Lauren 48:12

Yea, they make like a little web and then they deposit like a blob of sperm on it. And then they suck up the sperm with these like specialized sperm transfer organs.

Moiya 48:21

Fascinating. Any other consequences because we're near the top of the hour.

Lauren 48:27

Other consequences of -

Moiya 48:29

The stars changing?

Lauren 48:30

I mean, I feel like that's probably the worst of it for them. It's like the the star navigation is out for them. There's no chance, so they're gonna have to have like a really sophisticated navigation system and recording of the positions of the stars.

Moiya 48:47

I really hope that they can just feel all the wind. I wonder, how can we get the wind to be just like very consistent and regular on this planet? I don't know yet, but I'll think on it.

Lauren 48:58

All right.

Moiya 49:00

Any last thoughts, any last words that you want to say about the arachnid life form on this world?

Lauren 49:06

I mean, I just feel like it sounds like a world that I'd like to visit. To be honest, it sounds pretty awesome.

Moiya 49:13

Would you want to be there as a human observing or as one of these spiders living in the caves?

Lauren 49:19

I feel like I'd like to be a diplomat, and live in a special web house, that's all my own. [With] the most up to date architectural designs.

Moiya 49:30

Yeah, that's awesome. Well, thank you for telling me really cool things about spiders that I just did not know. They have glue. That's still blowing my mind. When our listeners want to learn more about you and what you do, how can they find out about your work? Where can they find you on the interweb?

Lauren 49:48

You can just look me up on the Cal Academy website. If you just Google "Cal Academy Lauren Esposito" you'll find me and the Cal Academy pretty regularly updates, like the projects that we're up to and stuff like that. If you want to follow my lab specifically, on Instagram we are @cas_arachnerds. And on Twitter I think my handle is @arachnologynerd.

Moiya 50:14

Awesome. Yeah, I'll put links to those in the show notes. And what else are you working on?

Lauren 50:18

Well, I am the founder of this visibility campaign for LGBTQ people who work in STEM called "500 Queer Scientists" and it's about to be Pride - the month of June. World Pride. So we have lots of exciting stuff planned, including the launch of an exhibit that focuses on intersectional identities of people of color, and LGBTQ identities that are also working in STEM. And we have 25 people that we're featuring with like long form narrative writing of their personal stories, videos, pictures, and really celebrating this intersectionality and how everyone's unique identity is a doorway rather than a barrier.

Moiya 50:58

That's beautiful.

Lauren 50:59

We're all about breaking down walls here.

Moiya 51:01

Nice. When is that coming out, because this episode will come out like June 17?

Lauren 51:07

So the physical exhibit is going to launch for the first time at the Cal Academy on June 24th. But it's going to be a resource that any museum all over the country or the world could put up in their own building for free, we'll share the design file. So if you want them, get in touch, and we have a web page that has like all the full information about every single person that's going to be launching in the beginning of June. The exhibit is called "New Science", because the old kind of science is a science of barriers and people being excluded and new science is kind of science where everyone participates. And lastly, that exhibit is going to be up in digital form also on the Google Arts and Culture website through Cal Academy.

Moiya 51:47

Those links will also be in the show notes. That's really awesome.

Lauren 51:50


Moiya 51:51

Thanks for doing that.

Lauren 51:52

Yeah, this is my thing that I do that I feel like it was made the most meaning.

Moiya 51:56

Oh, that's beautiful. How long have you been doing "500 Queer Scientists"?

Lauren 52:00

This is our third year anniversary, June 8.

Moiya 52:03

Happy anniversary!

Lauren 52:04

We've been running for three years. Yeah, we have accumulated the stories of 1,500 people who are queer in STEM.

Moiya 52:10

That's way more than 500.

Lauren 52:11

Yeah, we surpassed 500 the first month.

Moiya 52:16

That's awesome.

Lauren 52:16

So we're out here doing science.

Moiya 52:18

Yeah. And if "500 Queer Scientists" was an arachnid, at three years old, it would already be an adult.

Lauren 52:18

Yeah, it'd be having babies.

Moiya 52:28

Alright, well, thanks again. This has been really fun. I've learned a lot. That's a wrap.

Lauren 52:32

Thank you.

Moiya 52:36

Thank you so much to Dr. Lauren Esposito, an arachnologist extraordinare for helping me imagine this world full of touchy feely, cave dwelling arachnids who celebrate their molt days by going to a secret spa, and then having a big celebration afterwards. This has been such a treat, I've really enjoyed imagining this world. And here are three facts that we used in the construction of this world with an ever changing night sky. Fact number one, all arachnids molt their exoskeletons, they have these exoskeletons that are not made of exactly the same stuff as our skeletons. Instead, they're closer to nails or hair, but they have to come off so that the arachnid can grow over time. Fact number two, spiders have different kinds of silk. It's not just the same kind that is every spider web you walk into. So you know, be impressed that they can make different types of silk come out of their butts. I know it's not actually their butts, but that's really cool. Fact number three, is that in some species of spiders, the females are up to 30 times larger than the males. This is a form of sexual dimorphism, or the phenomenon of different sexes in a species having different physical characteristics. And one day, I would really love to build a world where there are more than two sexes or less than two sexes, I don't know. But that day is not today. If you're looking for a fun creative project, but you need a little bit of help getting those juices flowing, here is a hopefully fun prompt. We talked earlier in the episode about how maybe these arachnid creatures will build blankets or quilts out of their spider silk when someone is going on a long journey. What would your spider silk, long journey quilt look like? We are coming out of quarantine - hopefully soon. Maybe we'll be traveling again for the first time in a very long time. So if you were going to make a quilt for your upcoming travels or even your upcoming dream travel destination, what would that quote look like? Please share it on Twitter or Instagram with @exolorepod or you can send it to that's e x o l o r e I would love to see it. This episode of Exolore was edited by Mischa Stanton, the cover art is by Steven J. reisig. The transcript is by Iesir Moss, and the music is from Exolore is a member of Multitude productions, an independent podcast collective and production studio. I highly recommend checking out the other Multitude shows, all you have to do is type "Multitude" into the search bar of your favorite podcast app. If you want to support me and my worldbuilding work, the first way to do that is to rate and review the show on Apple podcasts. It's free, you don't need any sort of Apple device and it really does make a difference and help the show grow. Second, you can support me on Patreon. Your monthly support would make it possible for me to continue working on this passion project of mine. So if you're able, please head on over to "", again that's x o l o r e pod. If you can. Be sure to follow Exolore on Twitter or Instagram @exolorepod, and if you like this episode, share it with your friends and subscribe to the show because that way you can catch me next time on another world.

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