What is the biggest spider in the whole world

Imagine a spider as big as a child's forearm that weighs as much as a puppy. That's how huge the South American Goliath birdeater — arguably the world's largest spider — can be. Entomologist and photographer Piotr Naskrecki encountered one while he was on a nighttime stroll in the rainforest of Guyana, and at first he thought it was a small, hairy mammal. Here's a brief look at the fearsome eight-legged beast — arachnophobes beware! [Read full story on the Goliath spider encounter]

Spider in the hand

The South American Goliath birdeater (Theraphosa blondi) is the world's largest spider, according to Guinness World Records. Itslegs can reach up to one foot (30 centimeters) and it can weight up to 6 oz. (170 grams).

Defense mechanisms

The spider has three lines of defense. By rubbing its legs against its abdomen, it produces a cloud of tiny, barbed hairs that get in the eyes and mucous membranes and cause extreme pain and itching for days. It has two-inch-long fangs strong enough to pierce a mouse's skull. And it can make a hissing sound by rubbing its hairs together, which sounds like pulling Velcro apart.

"Birdeater"

Despite its name, the Goliath birdeater doesn't usually eat birds (although it's definitely capable of doing so.) Instead, it eats whatever it can find on the ground — usually earthworms, frogs, or other small invertebrates, injecting venom into its prey with its lengthy fangs. The spider does not pose much of a threat to humans, though a bite would be "like driving a nail through your hand," Naskrecki said.

Guyana specimen

Naskrecki encountered this specimen, a female, on a trip to Guyana, and captured her to take back with him. She is now stored in a museum. Naskrecki has only seen a total of three birdeaters in his career.

Scaring off predators

The Goliath birdeater has plenty of ways to scare off potential predators, including a behavior called stridulation in which it rubs the bristles on its first two legs and pedipalps together to create a hissing sound. The spider can also strike a spooky pose by arching the first two pairs of its legs back and "hinging back the fangs," so it's in perfect bite mode, according to the Natural History Museum. If that weren't enough, the Goliath can flick barbed hairs from its abdomen at potential enemies — the hairs can irritate the skin of such foes.

Growing up

The spiders take about two to three years go mature. And being a type of tarantula, the Goliath birdeater continues to molt into adulthood; that allows the creepy-crawlies to regenerate damaged or lost limbs, according to the Natural History Museum.

Up-Close

Here, a close-up look at a Goliath birdeater tarantula. The beast can grow as long as a child's forearm and weigh more than 6 oz. (170 grams), according to Naskrecki.

Huntsman Spider

Some sources say the giant huntsman spider, due to its sprawling leg span, is bigger than the Goliath birdeater. The huntsman's legs, rather than bending vertically relative to the body, have twisted joints that allow the legs to spread out forward and laterally sort of like a crab, according to the Australian Museum.

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.