10 Fascinating Things You Might Not Know About Spiders

The vast majority of spider species don’t pose a threat to humans—Australia and the Amazon are the hot spots for the deadly ones—and yet arachnophobia is one of the most common phobias in the world. But although spiders look fairly scary with their many legs and many eyes, they’re also fascinating animals. Here are 10 interesting facts that you likely didn’t know about the eight-legged creatures.

Related: 10 Strange Ways Insects Have Evolved To Survive

10 The Oldest Known Spider Lived for 43 Years

There are more than 40,000 spider species in the world, and most of them live for just a couple of years, but the longest-lived spider ever recorded made it to the grand old age of 43. Known as Number Sixteen, this female trapdoor spider (Gaius villosus) lived in a burrow in Australia’s North Bungulla Reserve. This species lives a sedentary life and rarely leaves its underground refuge.

Number Sixteen was first recorded in 1974 by arachnologist Barbara York Main, who was conducting a long-term study into trapdoor spiders. The burrows across the bushland were checked every six months, and, on October 31, 2016, researchers found that Number Sixteen had been stung by a parasitic wasp.

The spider was a staggering 43 years old at the time of her death, far outliving the other subjects in the study and the previous record holder—a 28-year-old Mexican tarantula.^[1]

9 Spiders Can Regrow Their Legs

Although known for having eight legs, arachnids can cope perfectly well with being a leg or two down. It’s not uncommon for a spider to lose legs throughout its lifetime, and they can even detach their legs themselves—a process known as autotomy—to escape the clutches of a predator.

But they can also regrow their legs, as long as they have at least one more molt—which is the shedding of their exoskeleton—left in their life. It usually takes two or three molts for the leg to be fully regrown, but even a shorter leg in the early stages of regeneration is helpful in a spider.

“We were surprised that an animal was able to ‘do its thing’ perfectly with a leg that is half its normal length and totally new—i.e., with muscles that have not exercised and sensors that had no time to ‘learn’ how to respond,” explains zoology professor Fritz Vollrath. The new leg can be used for moving around and even for web building.^[2]

8 It Can Rain Spiders

Some spiders have figured out how to take to the skies with the silk that they usually use to construct webs. When wanting to travel a vast distance, small spiders can crawl to a high point—such as a fence pole or a tree—and then send out silk strands to catch the breeze.

“It’s a reverse-parachute effect—they’re going from the ground into the air,” entomologist Robb Bennett explains. “It’s awe-inspiring.”

When the little arachnids then fall out of the sky, it looks like it’s raining spiders. The technique is known as ballooning, and while it isn’t noticeable if only a few spiders decide to relocate, it’s hard to miss when it happens en masse after an environmental disaster, such as flooding or fire.

“They fly through the sky, and then we see these falls of spiderwebs that look almost as if it’s snowing,” Keith Basterfield said after witnessing a ballooning event in southern Australia.^[3]

7 Brazilian Wandering Spider Venom Causes Erections in Men

The Brazilian wandering spider lives in the Amazon rainforest and is one of the most aggressive and dangerous spider species. Not only are they massive—with bodies up to around 1.8 inches long and legs up to 6 or 7 inches (15 to 18 cm) long—but they also dispense deadly venom in their bite.

This venom causes symptoms such as vomiting, convulsions, fever, and high blood pressure. But men who have been bitten by this spider are also subjected to another side effect: an hours-long erection. While that might not sound so bad, biomedicine professor Maria Elena de Lima explains that the venom causes a “prolonged and painful erection, which can lead to necrosis of the penis.”

Scientists have been studying this venom in hopes of extracting the chemical responsible in order to treat erectile dysfunction. Viagra doesn’t work for everyone, so it’s hoped that this new venom-derived drug will help more men.^[4]

6 Tarantulas Are Named After a Disease-Stricken Town

During the medieval period, a strange illness swept through the Italian town of Taranto. Sufferers experienced fatigue and apathy before slipping into a comatose-like state. The bite of the wolf spider was blamed, and music and dancing were thought to be the only cure for the disease, which was called tarantism.

Upon hearing lively music, the infected would start convulsing and dancing in an erratic manner. The frenzied dancing sometimes went on for days and, when the sufferer finally collapsed from exhaustion, they would wake up cured—although relapses often occurred. It was later discovered that the spiders weren’t to blame—their venom is no more potent than a bee sting—but by then they had become known as tarantulas after the name of the town.

The real cause of the illness remains a mystery. Still, anthropologist Ernesto de Martino suggests that it may have been a manifestation of deep psychological distress—abused women and widows were the most afflicted—and that dancing allowed them to release their emotions. Whatever the reason behind the illness, the dance lives on as a traditional Italian folk dance called tarantella.^[5]

5 There’s Only One Type of Spider That’s a Herbivore

It’s well known that spiders are carnivores, with flies and other small insects making up the bulk of their diet. Of all the thousands of spider species in the world, there’s just one that is a herbivore (well, mostly): Bagheera kiplingi. This small jumping spider—it measures just 0.2 inches (0.5 cm)—lives in the jungles of Mexico and Central America, specifically on swollen-thorn acacia trees.

Thanks to these trees keeping their leaves year-round, they provide a constant food source for the little spiders, so they don’t have to go looking for insects. B. kiplingi tends to survive by eating Beltian bodies—which provide protein and sugar—produced on the ends of the tree’s leaflets. They have also been known to sometimes eat acacia nectar, nectar flies, and the larvae of Pseudomyrmex ants.

Swollen-thorn acacia trees have a symbiotic relationship with these ants, with the spiders essentially acting as gate-crashers. The ants will attack other creatures that come into contact with the leaves, and in return, they receive food and shelter. The spiders are particularly good at exploiting this system, using their jumping skills to evade the ants.^[6]

4 Spider Silk Was Used to Create Crosshairs During World War II

The use of spider silk in optical instruments dates back to the 17th century, when fine threads were occasionally used in telescopes. By the start of the 20th century, it wasn’t uncommon to find spider silk in instruments that relied on visual accuracy, including levels and theodolites.

But it was during World War II that the usage of the material truly took off. Thin spider silk threads were used to create crosshairs for gun sights, airplane bomber sights, and submarine periscopes. Only certain types of spiders—such as black widows, European garden spiders, golden garden spiders, and lynx spiders—were drafted into the war effort.

So-called “spider ranches” began cropping up for the production of silk. One spider could produce up to one thousand feet of silk during its lifetime. But only the thinnest strands could be used for crosshairs, with the Bureau of Standards in America requiring threads to be one ten-thousandth of an inch in diameter.^[7]

3 One Type of Spider Lives on Mount Everest

Spiders are incredibly abundant and have even been found living in seemingly inhospitable environments. In 1924, explorer R. W. G. Hingston found a species of spider living on the slopes of Mount Everest at a height of 22,000 feet (6,705 m).

Hingston observed the tiny arachnids on snow-free rocks and stones. “I cannot think of what it lives at such a height,” he wrote in a New York Times article. “In these altitudes, there is no other living thing—nothing but rock and ice. This little spider is worthy of note as being the highest permanent inhabitant of the earth.”

In 1975, the hardy spider was officially named the Himalayan jumping spider, or Euophrys omnisuperstes, which translates to “highest of all.” It’s thought that their diet consists of tiny bugs blown up the mountain by strong winds.^[8]

2 At Least One Spider Species Produces Milk

Most baby spiders eat small insects, but at least one species produces milk to feed its offspring. Researchers at the Chinese Academy of Science wanted to figure out how juvenile Toxeus magnus, a type of jumping spider, were growing so large without leaving the nest.

“I saw a baby spider clinging onto its mom’s belly,” researcher Zhanqi Chen explained. “I had this radical idea that maybe spider moms feed their babies with something they produced.”

Chen and his colleagues gently squeezed some of the mother spiders, which expelled a small amount of white fluid that looked like milk. On analyzing the liquid, they found that it contained fat and protein, four times the amount of protein in cow’s milk.

For the first 20 days of their lives, the baby spiders depend solely on this milk-like substance. For the next 20 days, they eat a mixture of milk and insects—similar to human babies transitioning onto solid foods—after which they’re fully weaned. Researchers aren’t sure how exactly the mother spiders create the milk, but Chen hypothesizes that it might be recycled from unfertilized eggs.^[9]

1 Jumping Spiders Might Be Able to Dream

In 2022, a study investigated whether spiders might be capable of dreaming. The study’s authors, Paul Shamble and Daniela C. Rößler, noticed that Evarcha arcuata jumping spiders suspended themselves from silk threads at night and decided to examine what they were doing.

“We saw these regularly occurring bursts of activity that just looked or reminded us a lot about when you watch cats and dogs sleep or dream, where you just see these quite uncontrolled twitches,” Rößler told the Harvard Gazette. “Just everything about it looked like sleeping or dreaming to us.”

Muscle twitches are a strong indicator of REM sleep, but to gather more evidence, the pair recorded 34 baby jumping spiders—whose translucent bodies allow their retinal tubes to be seen—to determine whether they displayed characteristic eye movements. They did. It was the first time a dream-like state had ever been observed in a terrestrial invertebrate.

This evidence doesn’t definitively prove that spiders dream, but it does seem likely. “I assume that they’re dreaming about their own lives, like what happens to them during the day, the same way that we do—some strange visual version of their own experience,” Shamble said. “That’s pretty profound.”^[10]