Japanese Spider Crabs
Known as takaashi gani in Japanese, literally “tall-legged crab,” these guy are the largest arthropods on Earth. With legs one-meter (over three-ft) long, the result is a full leg span of over 12 feet (3.8 meters).
The reason these guys are only at number five is because they’re actually quite docile despite their monster-like appearance. They prefer to blend in to the bottom of the ocean floor by covering themselves with sponges and other sea animals, consuming basically whatever they can find.
Still, we’d rather not take our chances meeting one in person. These guys are found off the southern coast of Honshu, the main Japanese island, so we recommend staying out of the ocean there.
If you absolutely must see one of these things for yourself, then you can do so at the Osaka Aquarium.