Spider Sense Part 1: Unraveling the Secrets of Arachnids

Listen Now

Guest Information

Sebastian Echeverri is a communications specialist in science & digital media for the Xerces Society. Sebastian completed his PhD studying why and how paradise jumping spiders get their audience's attention when pulling off their fanciest dance moves. He has also written a field guide for spiders and has a collection of pet arachnids.

Show Notes & Links

In this episode, we discuss the diversity among the thousands of spiders in the world. We start with the basics of what makes a spider, a spider, from their anatomy to their behavior. We discuss jumping spiders' incredible vision and their use of silk.

• World Spider Catalog

Transcript

Matthew: Welcome to Bug Banter with the Xerces Society, where we explore the world of invertebrates and discover how to help these extraordinary animals. If you want to support our work go to xerces.org/donate.

Rachel: Hi! I'm Rachel Dunham in Missoula, Montana.

Matthew: And I'm Matthew Shepard in Portland, Oregon.

Rachel: Spiders. Some people love them and some people hate them. I don’t know much about spiders, but a few years ago I had a zebra jumping spider living in my car for a while. I grew rather fond of her and thought she was quite cute! We had some nice drives together.

Rachel: Joining us today to talk about jumping spiders, is Sebastian Echeverri, communications specialist in science & digital media for the Xerces Society. Sebastian completed his PhD studying why and how paradise jumping spiders get their audience's attention when pulling off their fanciest dance moves. He has also written a field guide for spiders and has a collection of pet arachnids.

Rachel: Thank you for joining us. We're so excited to have you here today.

Sebastian: Hey! Rachel, Matthew, thank you so much for having me. I am very, very excited to talk about spiders, which are my favorite animals, and then jumping, which are some of my favorite spiders.

Sebastian: This is one of the things that I—anytime I have a place where I could just talk about spiders, it's fun. So I'm looking forward to it.

Matthew: Yeah, no. I've been looking forward to this one, too, Sebastian, because I knew this was your special topic when you started working for us, but we've not really had a chance to explore it. So this is gonna be great.

Matthew: I know that we talk about spiders and other people kind of lump spiders together with insects and other creepy crawlies, as just, as bugs. But there really is a difference between the spiders and insects, isn't there?

Sebastian: Yeah, so that's a really great place to start with is—how do we talk about these animals? Because it's a thing that, if anyone is confused by it, there's good reason. A lot of people—like, this is not something that I ever got explained really well, until I was like at my grad school program, starting to study spiders. But spiders and insects are indeed quite different types of animals, but they're in the same overall genre of animals. So we separate, when we like study animals and stuff, we split them up into—they're called phyla, if you're using the fancy science term, or phylums.

Sebastian: I like to call them genres, because that's kind of, I think, a good—it gives you a good sense of what those groupings are. They're like—they're all united by one, usually one or two, traits that like distinguish them from the other genres of animals that have evolved. And spiders, insects, and a lot of other really, really fun animals are in the genre, or phylum, called arthropods. 

Sebastian: And so this is any animal that's got like a segmented exoskeleton. So that includes—basically, that is most animals. If you look at the difference—the number of species. But what we call that group varies a lot. I used to—and it's not something that's like often well-defined—I nowadays just call all arthropods bugs, because I think that matches closest to how a lot of people talk about them. 

Sebastian: Because people will call spiders bugs, people will call insects bugs, people call shrimp bugs, sometimes. And the thing that unites them all is that they are within this genre of arthropods. But within that genre you've got a lot of really fun evolution going on that's splitting certain groups away from others. 

Sebastian: And spiders and insects—even though they both have that segmented exoskeleton, even though they're usually roughly around the same size—the last time that they shared any DNA, the last time they had a common ancestor was—let me see if I'm remembering this correctly—I believe, around 550 million years ago.

Matthew: Wow. 

Sebastian: So that is way, way, way, way, way back in time, before dinosaurs, before anything. And to give that a sort of personal scale, you, the listeners to this program—who, I assume, are mostly humans, maybe some dogs and cats, and maybe some birds—you are all more closely related to sharks than any spider is to any insect. The last common ancestor of humans and sharks, I believe, is around 500, maybe 470 million years ago. 

Sebastian: And so if you picture a shark next to yourself, and you're like, those two animals are really different. There's like a few things that I can kind of squint at and be like, "Okay?" That's about what we're looking at between spiders and insects. And once you get a chance to take a closer look at a spider, you will be able to kind of notice and appreciate those differences. 

Sebastian: I feel like one of the other things that happens is that a lot of us don't have the opportunity, or are often discouraged from, you know, going up close and actually looking at a spider as more than a small speck or something. Or like a little thing moving around on the ground. And so we don't really notice the differences. But they are—if you look at their bodies, if you look at how their bodies work, how they're shaped, and everything—they are actually pretty radically different from insects.

Matthew: Yeah, I'm glad you brought it around to the differences there because one of the things in my head is if I see something on my living room wall, how can I tell if it's a spider, or something else, like a beetle or a cockroach?

Sebastian: Yeah, so it's actually pretty easy. There are two big things that are easy to notice even from a distance, and those are the kind of body sections or segments—like how big chunks of the body, let's say, how are they split up? And then the number of legs, and where they are attached. So if you look at a spider, it's got two big chunks of its body. It's got a head. And then it's got an abdomen, or a butt. And just—they're just like basically two balls joined together by like a little connection. And that, you know, will vary, depending on species, like which one's bigger, and the shape and everything.

Sebastian: But if you look at an insect, for example. They have three sections. So they have a head that is separate that has like a neck like ours, then they have a thorax or a chest, and then also an abdomen. And in some insects they've like really kind of weirded out how those are shaped. So sometimes the thorax and abdomen are hard to tell where one ends and the other begins. But if you see a head that is separate from the rest of the body with a neck, that is an insect.

Sebastian: The other thing that's related to this is the number of legs or limbs. So insects are famous for—you know, they have got six legs that they use for walking around. And those legs are all connected to their chest or their thorax. Spiders, on the other hand, actually have 10 limbs. They have two pairs of basically arms or pedipalps. And then they have the well-known eight walking legs that they use for getting around. And all 10 of those limbs are connected to their head—actually, the bottom of their head. 

Sebastian: Okay, so here's a model of a jumping spider, of a peacock jumping spider, and you'll see we've got—here's their head, the big eyes. These two, here, are the pedipalps, which in a lot of spiders are—I've called them arms. They're also used for reproduction. So they are the sperm organ in males. But they mostly pick up stuff, smell stuff, taste stuff. But they're little kind of arms, and like kind of right in front of the face.

Sebastian: And then all eight of the legs. If I take this little model here so I'm viewing the spider from the top, here's the head. Here's the abdomen attached by like a tiny waist. They have this tiny little tube waist that connects the two. And then at the bottom of the head are all the sockets for the legs. And so all of a spider’s legs are connected directly to the bottom of their head. And their head is basically just eyes, their fangs and their mouth, their legs, and then, you know, their throat. And then all of that, and their brain, that's basically all that's in the head.

Sebastian: And all of the like major organs, the things like heart, lungs, reproduction, digestion, all that good stuff happens in the abdomen. And so there's a lot of stuff that gets goes through the little tube waist to the back.

Sebastian: And so when you look at a spider up close, you see those legs attached the head. There's eight of them. And you may or may not see the pedipalps, 'cause sometimes they are small. But those eight legs that they're using for walking—that's a spider.

Sebastian: And the abdomen will just be a ball that has no legs attached to it. There's spinnerets back there, which in some spiders look long and maybe look like very short legs, but you'll note they're usually quite distinct from the actual legs.

Sebastian: The fun part of this knowledge... Now that you've listened to my little spider speech, you now know how to draw a spider better than, I would say, most things that you Google that have a spider on them. But very importantly, better than the original designers of Spiderman. So everyone, right now, go Google "original Spiderman logo." And use what you've learned to see the problems.

Sebastian: You will notice, if you find—there's some really nice graphics that have like the design changes of the Spiderman logo—probably the most recognizable “spider” across the world and one of the world's most famous superheroes.

Sebastian: The "spider" on his chest is not actually a spider for, I would say, about the first 10 years of the comic book's run, based on the illustrations that I found. And the dates that I found—it takes quite a while for them to be like, "Oh, wait. What if? What if this looked like what it actually is?" And then they go back and forth. I think in general, the newer logos tend to be more accurate, but there are some that people just slip back.

Sebastian: So now you can take that and have that little bit of superiority of, "Hey, I actually know more about spiders than the creators of Spiderman." Live with that and tell people about it. Because if there's one thing that bothers me, it's when I see a really cool depiction of a spider or it shows up in something that I love, and I'm like, "Oh, that's awesome!" And then I look where they put the legs. And it's like, if someone drew a horse with its like legs coming out of its neck or something, like it's that like to me. My brain just goes, "Oh, no! This is ruined!"

Matthew: Yeah, I was just gonna say that I totally get that. Because this has been annoying me for years. Because I work on insects. And my kids were small. And everybody was giving me like, you know, cuddly insects or toy insects or kids’ books about insects. And I'd look at them. And I'm like, you know, if this book was about puppies or kittens, and they were drawn as badly as that, no one would buy the book! You know? 

Sebastian: Yeah!

Matthew: And so yeah, no, thank you for making that point. 

Rachel: So on these episodes, we kind of like to get an idea of the diversity of the animals that we're talking about. So how many different species of spiders are there, first of all? And then what's the smallest and what's the largest?

Sebastian: This is another really fun one, because we recently hit the milestone of over 50,000 spiders—species of spiders in the last year or two. I think the current number is 52,000, and counting. If you want to see the most up to date thing, you can go to worldspidercatalog.com. And it is just an index of every spider. It's a very fun website. And you can access all of the research papers about any—or the taxonomy papers, at least—about these spiders for free if you make an account. But you can see the number tick up as spider scientists across the world are hard at work.

Sebastian: The smallest spider and the largest spider are very fun. Since we are recording, I'll get a piece of paper. What I needed is an 8 and a half by 11 piece of paper. 'Cause this is one of my favorite tools to show the diversity of spider size. Because the largest spider in the world, in terms of its leg span, is basically from here to here. If you go from the kind of like right front leg to the left back leg—of the one of the Goliath tarantulas that we have in South America, the genus Theraphosa—their leg span is about that diagonal of, you know, 12 inches at like maximum. 

Matthew: It would kind of sit on the piece of paper with its feet dangling off the edge.

Sebastian: Yes, yes, it would. I mean the body would be like a little ball would be here and here, and then the legs would go from there. I mean, if it really stretched out.

Sebastian: But then the other fun half of this is that if we find—this is probably in 12-point font, I'm assuming. So if we find a period at 12 point font right there. A period in 12-point font is about the size of the smallest adult spider in the entire world. But it is in the genus Patu. And there's—they're all kind of similar in size.

Sebastian: The one that is often stated as the smallest is Patu digua, which is from Colombia, just like me. And also the largest spider in the world also lives in Colombia. We get them both. But yeah, that is their adult size. They are incredibly small.

Rachel: Wow! That's amazing. I had no idea that spiders could get that small. And you said you could find them both in Colombia. So, obviously there's a lot of spider diversity, I would assume, in Colombia. Is there a reason for that? Are there hot spots of spider diversity? Any that you can think of in the U.S.?

Sebastian: Yeah, so in general, with animal—and I think this is true for all sorts of, at least plant and animal diversity—I will not presume about bacteria, but I assume they find fungi—I assume they follow the same rule—you'll find the highest diversity along the tropics, where there is just the most—basically the most energy available to play with.

Sebastian: You've got the most sunlight coming in, which makes lot more energy for plants, a lot more—which means there are a lot more different types of plants. And then it trickles down into the whole ecosystem basically. And so the highest concentration of diversity will be Central America and Northern South America, things like that. And sort of in that belt around the world generally, like different, you know—what the local geography is will like play with that.

Sebastian: But that's like a general rule for all plants and animals, and holds true for spiders, for sure. The—in terms of here in North America—it's a similar trend. So where you get further south in the Southwest and Southeast, they have different types of diversity. But that's where you find the most spiders, if you're just looking for a number of species.  

Sebastian: We have plenty. I'm here in New Jersey and we have a good number of spiders here, in terms of species. Probably, I want to guess at like maybe 200-ish, but in terms of what you see commonly, it'll be fewer. However, if you go further south and southwest, you'll get many more. But spiders can be found—even though that's a general trend, you know, where it's warmer, when the winters aren't as rough—because, just like all bugs, these animals get their heat from the outside world, from their environmental conditions. 

Sebastian: And so it's a lot easier for them when it isn't freezing cold outside. And so places where you don't have those winter, like harsh winters, usually you get more diversity. But that is a general thing. That isn't to say that there aren't spiders that have evolved to kind of hit every extreme that you can probably think of, except deep ocean. 

Sebastian: Because if we look at somewhere where you wouldn't expect to find a spider, on the slopes of Mount Everest, for example. There's a jumping spider that lives—oh, I'm trying to remember the exact number—it's something like—it's been found like something like I think 20,000 feet up the slopes of Mount Everest. And the Wikipedia will have the correct number, and I just don't have it up for me. But the species is a jumping spider called Euophrys omnisuperstes, which means the Euophrys jumping spider that stands above all others. Because it is above literally the rest of the world.

Sebastian: That is a jumping spider all the way up there, and then there are, I believe not jumping spiders, but other groups of spiders that have evolved to live underwater, in freshwater and even submerged in tidal environments. So there's like a trapdoor spider that lives in coral growing on mangroves, where it will make a trap door in the coral. And then, when the tide comes in, it closes it up. It's got a little underwater base, and then, when the tide goes out, it opens up and starts hunting.

Rachel: What!?

Sebastian: And so everywhere in between that, you've got spiders. Every continent on earth, now that we've brought them to Antarctica. And then every open ocean, sadly no spiders except on boats and the ones flying over the ocean. Because they—some spiders can balloon across oceans. But everywhere else you can find a spider. Which is honestly one of the fun things about them, because I can go literally anywhere and be like, "Oh, do I want to see some of my favorite animals? Yeah! They're already here."

Rachel: That blows my mind. Very cool.

Matthew: Yeah, it's the intertidal ones that I didn't know about. That's incredible.

Sebastian: They're very fun. Yeah, so there's a trap—the trap door is—most trap doors are not doing that kind of wild stuff. But that's why I like these guys. And then there's a whole family of—they're called the intertidal spiders—family Desidae, I believe. And they just love, you know, shoreline, salt water, intertidal stuff. And that's just their whole jam.

Matthew: Wow! But no, I was glad that the one at Mount Everest is a jumping spider, because that's your thing. I mean, it's what you studied in particular during your PhD and so on. Can you tell us a bit about jumping spiders? I mean, what makes them unique? I know we've touched on some of these things. And it's like, we haven't talked about silk, and I mean from what I know about jumping spiders, it's like they don't make a web. But do they still make silk in some way? I—you know—I don't know.

Sebastian: Yeah, that's a great point. And I'm glad I get to—thank you for sticking with me through all the general spider stuff. Now we're gonna talk about jumping spider stuff. Jumping spiders are their own family within spiders. And they're actually the most diverse family of spiders. So I said earlier, there's about 52,000 species of spiders. Around 11,000 of those are jumping spiders. 

Sebastian: So one fifth of all spiders are jumping spiders. And for context, for all of you vertebrates out there listening, birds—all birds, I believe—ooh, let me get my bird number. I believe all birds is something like 8,000 or 9,000, maybe 10,000? So there's more jumping spiders than birds.  

Matthew: Someone just hit the 10,000 birds for their life list. So it must be that many, but—.

Sebastian: Yeah. So it's around that many birds. And then—so there's more jumping spiders than species of birds. And then for things like mammals, like us, there's only about 5,000 species of those. And so jumping spiders have really got the diversity covered in terms of numbers, and they also come in many different shapes and sizes. 

Sebastian: But the thing that makes them really stand out amongst spiders, that really kind of sets them apart from most other spiders is, I would say, their vision. So jumping spiders are super cool because for most spiders, they're interpreting the world through senses that, for us, are like kind of like backup senses. So for most spiders, vibration and hearing and smell are their main way of like gathering information. 

Sebastian: And so that is really difficult for visual animals like us humans to sort of like, like get. Like it's hard to kind of put yourself in the mind of a spider, and like notice what they're picking up to because our brains aren't wired to pay attention to those things really well. But jumping spiders evolved to have ridiculously good vision for their size. 

Sebastian: If you see a jumping spider up close, they're very easily identifiable. They are a pretty short, stocky spider, where their legs are not very long, and they're pretty thick. And the biggest thing that is obvious about them is they have really big eyes. They have two pairs of eyes that are huge that face forward, and then two more that are relatively large on the sides of those, and then they have two eyes that face backwards, and two eyes that are small and face up. 

Sebastian: But those two biggest eyes are comparable in terms of their resolution—so like, how sharp the image is, how blurry or sharp it is—to—they are better or about as good or better than a house cat. And then to put that in terms of human vision, a jumping spider could just barely not fail a human vision test. So you know those 'we put some letters in a pyramid, stand far away and read them to me'? A jumping spider, despite being smaller than your eyeball, could pass that—could read at least the first row of letters at the same distance as you. That is the thing—it's like, not even up close, it's like at the same distance. Which to them is—you know they are—their body is like a hundred times smaller than you.

Sebastian: They are ridiculously tiny, and they have these really cool eyes. And that means that for them, their vision is really important. And so they've evolved to use their vision to explore the world. And that makes it very easy for us humans to notice the ways that they are smart. We can easily notice when a jumping spider is paying attention. We can easily notice when a jumping spider is curious about something. 

Sebastian: Because they will turn. They will watch it. They'll do the like puppy dog thing of like cocking their head a little bit to like investigate from different angles. They will creep up on things, and, like, you know, watch and sneak up and like observe stuff. They will notice when we move and respond to it. They will follow a laser pointer, if you wanna play around with one. I think I found that green laser pointers work best. 

Sebastian: But they are so similar to animals that are easy for us to understand. It's very—they're very accessible in terms of like figuring out what's going on their head and kind of like empathizing with them, which is really important for a lot of people. But they're also, I mean, ridiculously cool in that like, in kind of sort of what they do. Because it's not just that they have these eyes. 

Sebastian: I should note, the reason that they can see so well, despite being—so a jumping spider, I would say an average size adult jumping spider is maybe the size of like the length of your pinky nail (depending on how big your pinky nail is), but like that's not—that's probably bigger than your average. But, of the ones that you'll see, that's about their whole body. And then so their eyes will be about a millimeter to two millimeters deep, or big. And yet they can see, you know, almost as well as an animal that is like 20 to 100 times their size. And better than many animals much, much bigger than them. So a jumping spider can see better than like an elephant, for example, or a camel, or many birds. 

Sebastian: And the way that they've done this is that they actually evolved telescopes, millions and millions of years before humans invented telescopes. So if you look at a jumping spider’s—the big eyes, the big ones. They're not balls like our eyes. Because they needed to have enough room for a second lens. And so they have—there's like an outer lens that's part of the exoskeleton, and they have an inner lens. And then the inner lens actually, like a telescope, like expands the image back up as it's getting projected onto the back of the eye.

Sebastian: And so their field of view with those eyes, much like if you put a pair of binoculars to your face, the field of view is much smaller than if you didn't have those binoculars there. But you can see further away things that were smaller and much more clearly. And they sort of do that, except that they don't necessarily have the tradeoff of losing the rest of the field of view, because they just have other eyes on the corners of their heads.

Matthew: I was going to ask that. How do these other eyes work? With the binoculars at the front. Do they all shine into the same space? Or is it completely separate and their brain processes it? 

Sebastian: That is a good—that is a really good point. There's some insects that have really weird compound eyes where different openings will feed to the same retina. Each eye on a spider, and each eye on a jumping spider as a subcategory of spiders, will work the same way more or less, and they work like our eyes. They are what we call a camera-type eye where it is a single lens usually. 

Sebastian: With—so there's a single opening with a single lens that focuses an image onto a retina. And they're usually, you know, some variation of a very kind of flat oval, or a larger ball, if it's a spider that has better vision. Or sometimes tube-shaped, when you need to pack in a lot of things into a smaller space. And so they work like our eyes. They're not compound eyes. 

Sebastian: And our understanding, roughly, of how a jumping spider is interpreting this—because they have two big eyes, two other pairs of eyes next to those that also kind of face forward and out, and two backwards—is all of those are interconnected. Like the wiring from those goes both to the spider's brain, and to the other eyes.

Sebastian: So if a jumping spider sees something move behind them—'cause the four eyes in the corners of their boxy head, all of those eyes are really sensitive to motion—it will both send a signal to the brain, but then it'll also send us a signal to the primary eyes and to the legs. And it'll say, at, you know, roughly—what would that be...like 5 o'clock, 6 o'clock—there is something that is roughly shaped like this in this part of your field of view. 

Sebastian: And then the whole spider will swivel around, and like almost instantly. And it'll point—the jumping spider will point its primary eyes, those two big ones, and it'll lock right onto that target. Because it's already heard from the other eyes roughly where that thing will be, and roughly, what it's going to be shaped like. 

Matthew: Yeah. I was thinking it's almost like security cameras, you know? You've got multiple screens. And then it's like, "Oh, something's over there. So we'll turn and look."

Sebastian: It's a little bit like that. Some of the fields of view of those eyes do overlap, so they can get some amount of like binocular vision. So there is some like processing going on. But it is—if you had, you know, like, security cameras lined up in a row, right? And they're all facing in four different directions, and they just barely touch where they're pointing—would give you a similar experience, roughly.

Sebastian: And so, because of all these eyes, they hunt with their vision. They hunt by sneaking up on things and spotting them from a distance. And they don't hunt with webs, to get all the way back to your original question.

Sebastian: One of the things that makes a spider a spider is that they have spinnerets on their abdomen. So these little like leg- or finger-like little things on the tip of their abdomen that makes silk. So if you have spinnerets that make silk, that is one of the traits that like unites all spiders. And all spiders have fangs and almost all spiders have venom that they inject with their fangs. Jumping spiders have venom that they inject through their fangs, like the vast majority of spiders. There's like one, I think, family that doesn't. But that is like the two big main spider traits.

Sebastian: And so what a jumping spider will do is their silk is—like many other spiders that don't hunt with their webs, they still can make silk, and they still can make a web-like material, but they use it for—often for building a little home. So they'll build shelters and retreats. They'll like curl up a leaf and like fold it over and then like web it down and make like a tunnel, or like make a sleeping bag in a corner, or like under something. They use it to wrap their eggs when they lay eggs. And they also use silk when they're jumping.

Sebastian: So I've gone into like—I don't know how long I’ve been talking about jumping spiders and haven't mentioned the jumping. They jump! It's kind of their thing. They jump forward more than up. So they will—they have like a standard jumping position that they get into when they're trying to do a good jump. But they basically kick out of their last pair of legs very quickly. And that kick forward launches them at high speeds that they can control how far their jump wants to be. But they will launch their jump, and then they actually can use that silk as a safety line. 

Sebastian: So when a jumping spider moving around—they can climb on like all surfaces also—but they're always leaving a safety line that is like—they attach it to a surface, and then it just like unspools from their spinnerets as they move. And so if they fall, or they miss a jump, they just catch themselves on the safety line and like climb back up.

Sebastian: And there's some evidence that they can actually, mid-air, correct on their jumps. So if like they're jumping and they're like, "Oh, I'm gonna overshoot," they can pull on their safety line to like change their trajectory, so that they can land. And that's the main way they use their silk.

Sebastian: One of the really cool things about spiders in general and about the diversity of them is that they take these two things—having fangs that usually have venom in them and having silk—and then just go in vastly different directions of what we're gonna do with that. If anyone's a fan of like the Spider-Verse series of movies, where like, "Oh, there's different versions of Spiderman" and they all kind of have like the same like core thing, but like because of their setting, because of whatever powers they got, like have a totally different take on the character. That's basically spiders. That's like basically just what spiders are.

Sebastian: And they're just doing that all the time, sometimes, often with powers that are the same, or better than Spiderman's powers. But that sort of energy of like, "Oh, this is familiar, but like you have like a whole different spin on it" is a really fun thing about just learning about different spiders and noticing how they're using those things differently.

Rachel: Thank you so much Sebastian and to our listeners. Join us on the next episode of Bug Banter, where we will continue the conversation and explore paradise jumping spiders, myths about spiders, and what you can do to help these fascinating creatures.

Rachel: Bug Banter is brought to you by the Xerces Society, a donor-based nonprofit that is working to protect insects and other invertebrates—the life that sustains us. 

Rachel: If you’re already a donor, thank you so much. If you want to support our work go to xerces.org/donate. For information about this podcast and for show notes, go to xerces.org/bugbanter.