8 Incredible Facts About Tarantulas

Tarantulas are the largest spiders living on Earth today, growing to sizes that intrigue some people and terrify others. They exist on a different scale from most of the spiders we encounter, forcing us to confront how alien — yet also how strangely endearing — spiders can be.

In honor of these massive and misunderstood arachnids, here are a few interesting things you may not know about tarantulas.

1. Nearly 1,000 Species Are Known to Science

True tarantulas belong to a large spider family called Theraphosidae. There are 987 species across 147 genera, most of which inhabit the tropics, subtropics, or deserts. South America is home to the largest number of tarantula species, but these spiders are more diverse and widespread than many people realize, inhabiting every continent except Antarctica.

2. The Word 'Tarantula' Has a Strange Origin

The first spider to be called a "tarantula" was actually a type of wolf spider, Lycosa tarantula, which is not a member of the family Theraphosidae. It's native to southern Europe and was given the name tarantula centuries ago as a reference to the city of Taranto in southern Italy. A type of dancing epidemic known as tarantism was prevalent in southern Italy between the 15th and 17th centuries, and many people at the time reportedly believed it was caused by a bite from these wolf spiders.

While the exact cause of tarantism and other dancing plagues remains unclear, the link to spider bites has long since fallen out of favor. The word tarantula endured, however, and later came to be applied to other large, hairy spiders in Theraphosidae. The dancing itself, which has been variously described as a symptom or treatment for the spider's bite, helped give rise to the famous Italian dance known as the tarantella.

3. They're 'Hairy,' but That Isn't Really Hair

One of the most distinctive traits of many tarantulas is the presence of bristly hairs on their bodies, including their legs. Although this looks like hair and is commonly described as such, spiders and other arthropods do not have true hair like mammals do. Mammalian hair is mainly made of keratin, while arthropod setae consists largely of chitin.

4. Some Fling Barbed Bristles as Weapons

Many tarantula species have a special kind of setae, known as urticating hairs, that serve as a defensive weapon. Not only can these bristles rub off on a predator when it makes contact with a tarantula, but the spider can also actively flick them at troublemakers with its legs. The bristles are barbed and can become lodged in the eyes and mucus membranes of the recipient, causing irritation and pain.

About 90% of New World tarantulas have urticating hairs, often with multiple types that seem to have evolved for fending off different predators. Some urticating hairs are more effective against invertebrates, for example, while others are mainly deployed against vertebrate predators. Tarantulas from other parts of the world do not have urticating hairs, and in lieu of this defensive technique, they often respond to threats with more aggressive posturing than their New World counterparts.

5. They Pose Very Little Danger to People

Tarantulas are widely typecast as dangerous, a perception often reinforced by movies and TV. Yet while their large bodies and fangs can make them seem monstrous, and they do possess venom, most tarantulas are not dangerous to humans in real life, especially New World species. (It's worth noting, however, that some large spiders commonly confused with true tarantulas have more toxic venom.)

Like most spiders, tarantulas rarely bite humans, and will almost always flee if they have the option. A typical bite from a tarantula is comparable to a bee sting, with only local and temporary pain and swelling. No North American tarantulas are thought to pose even a mild danger to humans, nor are any of the species commonly kept as pets. Some African and Asian tarantula bites have been reported to cause moderate illness, but there have been no reported human deaths due to toxicity from a tarantula bite.

While the venom itself may not be dangerous to humans, however, it can trigger allergic reactions in some people. The urticating hairs of New World tarantulas can cause skin rashes or inflammation of the eyes and nose, but that can generally be avoided by not antagonizing tarantulas and keeping your face away from them.

6. Some Tarantulas Prey on Small Vertebrates

Tarantulas are ambush predators, pouncing on prey rather than trying to snare it in a web. They do produce silk, although it's mainly used to line their burrows or for specialty purposes during mating and molting. Tarantulas typically eat insects and other small invertebrates, but their diets vary depending on the species' size and habitat. Some larger tarantulas are known to prey on small vertebrates like frogs, lizards, and even rodents.

A South American tarantula known as the goliath birdeater is widely considered the most massive spider alive today, growing up to 11 inches (28 centimeters) in diameter. Despite its common name, however, it only rarely preys on birds, instead feeding mostly on earthworms, insects, and other invertebrates.

7. They're Hunted by Wasps Called Tarantula Hawks

Tarantulas may seem intimidating, but these hulking spiders are still commonly eaten by an array of animals. Many generalist predators are known to prey on tarantulas, including snakes, lizards, frogs, and birds, as well as mammals such as coati, opossums, mongooses, foxes, and coyotes.

Tarantulas are also the primary target of some specialist predators, namely a group of spider-hunting parasitoid wasps known as "tarantula hawks." These large wasps sting tarantulas to paralyze them, then lay a single egg on the spider's body. The wasp then seals its victim in a burrow, where its offspring will feed on the still-living but paralyzed spider once it hatches.

8. Some Tarantulas Can Live for 30 Years

Tarantulas are long-lived spiders, although their life spans vary by sex as well as species. Male tarantulas may live for as long as 10 years, but once they successfully mate, they usually die within a few months. Female tarantulas, on the other hand, have been known to live for 30 years.