Piotr Naskrecki was taking a nighttime walk in a rainforest in Guyana, when he heard rustling as if something were creeping underfoot.
When he turned on his flashlight, he expected to see a small mammal, such as a possum or a rat.
“When I turned on the light, I couldn’t quite understand what I was seeing,” said Naskrecki, an entomologist and photographer at Harvard University’s Museum of Comparative Zoology.
A moment later, he realized he was looking not at a brown, furry mammal, but an enormous, puppy-size spider.
Known as the South American Goliath birdeater (Theraphosa blondi), the colossal arachnid is the world’s largest spider, according to Guinness World Records.
Its leg span can reach up to a foot (30 centimeters), or about the size of “a child’s forearm,” with a body the size of “a large fist,” Naskrecki told Live Science.
And the spider can weigh more than 6 oz. (170 grams) — about as much as a young puppy, the scientist wrote on his blog. [See Photos of the Goliath Birdeater Spider]
Some sources say the giant huntsman spider, which has a larger leg span, is bigger than the birdeater.
But the huntsman is much more delicate than the hefty birdeater — comparing the two would be “like comparing a giraffe to an elephant,” Naskrecki said.
The birdeater’s enormous size is evident from the sounds it makes. “Its feet have hardened tips and claws that produce a very distinct, clicking sound, not unlike that of a horse’s hooves hitting the ground,” he wrote, but “not as loud.”