What's the Biggest Spider in the World?

By: Jesslyn Shields  | 

goliath birdeater spider
The Goliath birdeater spider (Theraphosa blondi) weighs in as the world's largest and heaviest spider. Yikes! PetlinDmitry/Shutterstock

Common names of animals aren't known for their precision, and sometimes they're just plain misleading. For instance, a flying fox is just a big bat, ringworm is actually a fungal infection, jellyfish aren't fish, and sure, anteaters eat ants, but they consume more termites and other insect larvae than ants. The Goliath birdeater? Well, this spider is huge, but it doesn't eat birds often enough to warrant the name.

But at least half of the Goliath birdeater's name is accurate — it's a real giant: the largest and heaviest spider in the world. Native to northern South America, this rainforest tarantula weighs about as much as a hockey puck and has a body length comparable to a mid-sized smartphone — not to mention a leg span of about 12 inches (30 centimeters). They are truly gigantic, but relatively harmless to humans. Even though they have long fangs that can pierce human skin, their venom isn't particularly toxic to us, or indeed to many would-be rainforest foes.

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Which is why the Goliath birdeater has a different tactic for shooing away would-be predators: hair missiles. When threatened by a snake or curious mammal, they rub their back legs against their abdomen, releasing missile-like hairs that cause extreme irritation to skin (in the case of humans, who are relatively hairless compared to other animals), eyes and other mucus membranes. The rubbing of their legs against these hairs is a warning in itself — it can be heard by humans and animals alike from up to 15 feet (4.6 meters) away. Called stridulation, it is the same behavior used by crickets and grasshoppers and crickets to make their chirping noises.

Although the Goliath birdeater has a reputation for munching on the feathered population, it rarely has the opportunity to eat a bird, though it probably wouldn't turn one down if it arose. Like other tarantula species, the birdeater doesn't make webs — they're forest floor hunters, going out alone to find insects, frogs, mice or lizards every night. When it finds something to eat — basically anything smaller than it is — it bites it with its long fangs and delivers a dose of neurotoxin that incapacitates the animal so the spider can drag it back to its burrow, because the rest of the process is too gross to complete in public. Once at home, the Goliath birdeater lets the neurotoxin do its work, liquifying the animal's insides. Once that's been accomplished, it sucks out all the juices. Yummy.

Goliath birdeaters are prized in the exotic pet industry and are surprisingly long-lived. The males can live between three and six years in captivity while the females can live up to 20 years.

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