10 Amazing Biologist-Approved Spider Facts

Whether we find them intimidating or intriguing, people can’t deny some interest in spiders. They’re a part of our lives whether we like it or not, and play a critical role as insect predators in many ecosystems. Beyond that, spiders can be a homeowners’ or gardeners’ best friend for their ability to control potentially harmful insect pests. As someone who was relatively frightened of spiders as a kid, I have crossed the aisle to really enjoying these animals in their many forms and behaviors. A few years of work as a field biologist getting up close and personal with spiders in beautiful locations throughout the world didn’t hurt either. When you’ve woken up with a palm-sized spider sitting on your chest in the middle of the Costa Rican rainforest, a couple spiders in the corner of your ceiling don’t seem so bad!

Regardless of your feelings about them, spiders have a lot of amazing claims to fame, and their science and natural history is a goldmine of cool nature factoids. Unfortunately, as with many other nature blogs nowadays, information is recycled by AI and not vetted by experts. To solve that problem, here’s another biologist-vetted Wildlife Spotlight giving you trustworthy facts from my reading, research, and experiences as an ecology professor and naturalist. We’re long overdue a post focusing on spiders at Gulo in Nature, and my hope is that some of the fascinating spider facts below will help you enjoy them as much as I do.

1. Young spiders fly using electricity

While panic-stricken clickbait articles on “flying spiders” are common on the internet these days, there are some grains of truth to the matter. Let’s get one thing straight first, however: spiders do not have wings! In fact, spiders have never had wings in their evolutionary history, and fossil evidence shows that some groups of spiders are very similar to those found even tens of millions of years ago. However, if you’re super small, you don’t necessarily need wings to fly.

Flying spiders are much more common than you might think. In fact, most spider species “fly” in the early stages of their lives, what scientists call the dispersal stage, when young animals strike out on their own to find a place to live. Spiderlings, as baby spiders are called, are super tiny, and like other kinds of animals have to find their own home and resources away from their parents (and potentially cannibalistic siblings!). To get airborne, these tiny spiderlings don’t need a lot of force, so wings aren’t necessary. Instead, they use a technique called “ballooning”:

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The spiderlings climb to the top of some high object where they can access moving air, and put out small strands of silk into the air. It was originally thought that these strands caught the breeze and whisked spiders away like parasailers. That is, the drag on these strands caused by the moving air would pull them into the sky. Instead, scientific studies show that instead the forces which make these spiderlings fly involve electrical as well as drag forces. As it turns out, the Earth’s atmosphere has a slight positive electrical charge, which opposes a negative charge on the ground. The spider’s silk, when releases, also carries a negative charge, which helps pull them into the sky in addition to the drag from their “sail”.

But there’s more! Researchers investigating the electrical nature of spider ballooning found that not only can spiders sense electrical currents using specialized hairs on their legs, but that they also have a system to “test the waters” before setting sail. Just like a Boy Scout wetting a finger and raising it into the air to test wind direction, they also check before takeoff. By climbing to an exposed perch like the top of a tall plant or fencepost, the young spider actually finds a place where the electrical field between the Earth and atmosphere is strongest, making advantageous conditions for takeoff. Belaying themselves with an “anchor strand” of silk to their perch, they raise their sensitive front legs to test the wind speed and surrounding electrical field. If this sounds good, they’ll cut their anchor strand and away they go!

Fascinatingly, the silken strands that these spiders use for ballooning is a mess of many different lines coming out in parallel. Because of their similar static charge, they repel one another and don’t get tangled up, but fan out and stay parallel. This makes them a very efficient “sail” to bring the spiderling long distances and high in the air; ballooning spiderlings can get as high as 12,000 feet (~3600m). If they get high enough into the air, ballooning spiders can get caught up in atmospheric jetstreams, and transported thousands of miles. This is believed to be the way that spiders have reached remote islands like Hawai’i, where they are found even at the tops of barren volcanoes like Mauna Loa.

This incredible ability to disperse around large landscapes is part of why introduced spiders can so quickly become invasive species. Once they get established in one place, young spiderlings will quickly fan out and can cover a lot of ground!

Read more: Facts about the Invasive Joro spider in North America

2. Not all spiders spin webs

Among the major things that set spiders apart from other invertebrates, and especially their closer cousins within the Arachnid class, is their spinnerets: a collection of specialized organs that help them produce and deploy silk. On spiders, these spinnerets are located at the back end of their opisthoma (read: butt), and there can be between two and eight of them, capable of moving independently, depending on the type of spider. With more than 53,000 described species of spider on Earth, if you figure that spiders might have some very different ways of using these important organs, you’d be spot-on.

In fact, probably less than half of spider species produce the spiderwebs, but instead use have all kinds of creative hunting strategies. A great many of these nonetheless involve taking advantage of their silk-making superpower, but are a far cry from the classic orbweaver pattern you might know from Charlotte’s Web. For example, jumping spiders (Salticidae) hunt down their prey on foot, pouncing like tigers upon unsuspecting insects. For some of their more acrobatic maneuvers, they anchor themselves with a strand of silk to use as a lifeline in case they miss! Although tiny jumping spiders are unlikely to be hurt by a fall, it always helps to have a bungee cord to get back to their hunting perch.

By contrast, wolf spiders (Lycosidae), also active hunters that chase down prey, use their silk to make a “backpack” to carry their eggs around. Given their highly mobile, nomadic lifestyle, this allows wolf spider moms to carry their brood around in a “sling” so they can keep right on moving. Tarantulas, one of the most impressive and maligned of spiders, tend to use their webs to line tunnels or hiding places for better shelter. Keep reading for more creative uses of spider’s silk!

3. There are aquatic spiders—and some of them are huge!

As someone who is particularly fond of wetland and pond habitats, my favorite spiders are the ones that hang out near water. There are actually many spider groups that do so (after all, there are lots of bugs near water!) and all of them in creative and interesting ways. Since aquatic habitats provide such an ample food supply, it might also come as no surprise that aquatic spiders include some of the largest ones you’ll come across in much of the world.

Throughout the world, spiders in the genus Dolomedes are common around water, where they hang typically hang out near emergent vegetation or along the water’s edge. They rest on top of the water’s surface, feeling the surface tension with sensitive hairs on their front legs. This allows them to get a feel for what prey is around, and when they feel something promising they run out (walking on water, by the way!) and grab it. Although they mostly eat aquatic insects and those that fall into the water, larger Dolomedes will eat small fish, tadpoles, or other hapless small vertebrates they can get their claws on. These large, brown spiders often have leg-spans of 3 or more inches across, with body lengths 1-2 inches or more. Their large size and frequency near water has earned them nicknames like dock spider, wharf spider, and fishing spider.

4. Spider silk has a higher tensile strength than steel

Tensile strength, the ability for a material to withstand a pulling or stretching force, is an important quality for engineering and construction. Spider’s silk, with which spiders build a variety of clever structures, including most their webs, has a reputation for being especially strong. The seemingly wild claim that spider web is stronger than steel of an equivalent width does in fact hold water, unbelievable as it is. Of course steel in any form we encounter it is much stronger than spider’s silk, but relative to its size, spider’s silk ability to stretch and withstand pulling (tensile strength) is superior. What’s more, spider silk achieves this fantastic strength while being thinner than a human hair! Recent studies on the structure of silk from recluse spiders (genus Loxosceles) and house spiders (genus Kukulcania) shed some light on the issue.

Importantly, like many other very strong cordlike materials, a strand of spider web is actually made up of many thousands of much smaller strands which, woven together, can withstand a lot of force. These nanofibrils form a sort of mesh woven into a complex pattern around a larger central strand, making for a super sturdy nano structure. These details are so tiny that a fantastically powerful form of microscopy called atomic force microscopy (I mean dang, what a name!) was necessary for researchers to image it. Beyond their strength, these nanofibrils are also terrifically stretchy, giving spiderwebs tremendous resilience in the face of forceful shocks like moths or other small insects striking the web.

For me at least, these fascinating details make webs in the garden or cobwebs on the ceiling a little more fascinating.

5. Web-spinning spiders have special claws for walking on webs

Spinning webs for a living is serious business. Web-making spiders have to carefully build and maintain elaborate and complex traps with complicated structures and then navigate them safely to catch prey. Aside from non-sticky structural strands that provide the incredible strength we already mentioned to spider webs, other strands provide the capturing power. When insects get caught in a spiderweb, it’s not just that they get tangled up, but some strands are sticky and adhere to their wings and bodies.

Fascinatingly, this deadly sticky-trap mechanism is believed to be why butterflies and moths have so many scales that come off so easily. These scales come off on the sticky parts of the web, allowing the insect to escape with its life. But how do spiders keep from getting stuck in their own webs?

A closer look at the legs and feed of web-making spiders versus the many species that don’t make webs is helpful here. Interestingly, the spiders that make webs typically have three “claws” at the end of their legs, while spiders that don’t make webs only have two. This extra claw is actually opposable, which allows the spider to punch the web strand between it and a neighboring claw, which typically has special microscopic serrations for gripping web. Using their specialized claws, web-spinning spiders walk easily across their webs when other animals would get stuck.

6. Ancient spiders went gangbusters after flowering plants came on the scene

The cretaceous period, which was the last major geological epoch when dinosaurs were around, was also the time that flowering plants (Angiosperms) appeared on the scene, providing nectar resources for pollinating insects. This apparently led to a huge increase in flying insects in response to these new resources, which left an ecological gap for predators. A huge number of web-spinning spider groups suddenly appear in the fossil evidence around this time, indicating a probable response to that vacant role, what ecologists call a “niche”.

Fossil and molecular evidence suggests that spiders quickly diversified during the dinosaur’s closing chapter, splitting into many different groups with different approaches to capturing prey as insects increased in ecological prominence and diversity. In that way, we may owe our thanks to flowering plants and a rapidly changing planet several dozen million years ago for the richness of cool spider species we see today!

7. There is a spider species named “Hotwheels sisyphus”

This one speaks to itself and is one of my favorite ridiculous nature facts. Weird animal names are a great reminder that scientists are everyday people who like to have a good time just like everyone else. They have a sense of humor, even if it might not necessarily be a particularly good one. One of the most exciting privileges for biologists like myself is getting to describe, and potentially even name, a new species when it’s discovered.

Researchers in China recently described a new species of spider that belonged to an entirely new genus, meaning that both of these designations needed a new name. Investigating museum specimens of spiders collected from Southwest China they found some individuals that didn’t match any known species. Upon further inspection, they found characteristics of their internal organs that didn’t match any other known spiders. This included an organ that had a long, coiled shape, which one of the scientists likened to the loop-de-loop of a Hotwheels car racetrack!

Read more: Gulo in Nature’s Weirdest Nature Facts

8. Some spiders “fish” for moths

Okay, this was a new one for me; this spider fact was cool enough that it deserved its own separate heading. Returning to the subject of spiders that don’t spin webs, I would be remiss not to mention the bolas spider, (Mastophorini), a small group in a web-building family of spiders that uses their silk very differently. Named after bolas, a throwing weapon employed by Indigenous peoples of South America to capture running animals by entangling their legs with weighted balls connected by a cord, these spiders fashion their own ingenious hunting weapon.

Female bolas spiders hang from a leaf or twig, “holding” a strand of silk in one of their front legs. Attached to the strand is one or more “capture blobs” (that’s actually what naturalists call them, I love this) of sticky fluid. As I mentioned above, moth’s wing scales give them an advantage when escaping normal spider webs. However, bolas spiders specialize in catching moths. They do this by attracting male moths to their bolas, the blobs of which can exude a smell that resembles that of female moths. When the moth draws near in the hopes of finding a mate, the spider swings the bola, attaching the capture blob to the moth and then reels it in. Somewhere between fishing and bola-throwing, this impressive technique works very well where webs fail to reliably capture moths.

As if bolas spiders couldnt get any cooler, here’s one more detail. As nighttime hunters, they need to hide during the day to avoid falling prey to hungry birds. Most bolas spiders stay safe in daytime by standing very still and relying on camouflage. Instead of blending into their surroundings, they often have shapes and colors that make them look like bird poop, the last thing most birds are looking to chow down on.

Read more: Stunning Examples of Animal Camouflage

9. Aquatic spiders construct silk “diving-bells”

One unique spider species that lives in aquatic environments in Europe and Asia has taken its pond-loving habits to the next level. Argyroneta aquatica, also known as the water or diving bell spider, is the only true spider that actually lives a fully aquatic life. That is, rather than living in the air around water, it spends almost all of its time below the surface. These spiders are so into their “life aquatic” that they even breed and lay eggs underwater.

But without gills, how do these spiders live fully underwater? The answer, revealed by one of their common names, is by having a mechanism like a diving bell or SCUBA tank. The spider’s rear ends are covered in a dense layer of hydrophobic hairs that resist wetting. These trap a bubble of air around the spider’s opisthosoma (again, read: butt), which is also where its breathing parts are located. Oxygen from the surrounding water can diffuse into the bubble and carbon dioxide can diffuse out as the spider breathes, leaving a good balance of air to breathe. More importantly, these spiders create diving bell shelters attached to underwater vegetation, which do this on a larger scale. These use a sheet of silk to maintain a structure that holds in oxygen, and which they can return to repeatedly to get fresh air as needed.

Unlike many spiders, in which females are often a lot larger and more aggressive than males, the opposite is true for diving bell spiders. Males are very active swimming hunters, taking on a variety of prey including mosquito larvae and small aquatic crustaceans like water fleas.

10. Jumping spiders have incredible vision

Spiders’ eyes are one of the features that varies the most between species. In fact, examining the positioning of a spider’s eight(-ish) eyes relative to one another is a great way to tell species or families apart. For those spiders that hunt down prey by sight, those eyes become extremely important. Just as visual predators like tigers, wolves, hawks and owls. Scientists describe such highly effective eyes as “camera like” because they have a fovea, or a “pit” of small, dense light-sensitive cells at the back of the eye. This fovea is what lets us focus visually and with great detail on one point in our vision at a time.

Read more: Amazing Facts About Owls

Amazingly, jumping spiders are the only invertebrates that have this amazing adaptation. Two of their four sets of eyes, the major ones in front and two on the sides, have this characteristic, and provide them with fantastic depth perception and very acute vision for identifying and tracking objects and understanding their surroundings. Despite their comparatively tiny size, these eyes can pick up movements and achieve detail nearly as sharp as way larger vertebrate eyes. Although they can’t see with as broad a field of vision as much larger organisms, the fact that their eyes perform so well despite being hundreds of times smaller is astonishing.

Jumping spiders’ large primary eyes also give them a cute, puppy-like appearance that makes them more endearing and less intimidating than other spiders. This has led to them becoming popular pets among invertebrate enthusiasts, although they don’t tend to live very long.

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