Kaua'i Cave wolf spider
Only known to live in a few lava tubes on the Hawaiian island of Kaua'i, this eight-legged predator is called the blind wolf spider by locals and is one of the rarest creatures in the world. In fact, researchers have never documented more than 30 spiders at a time.
The wolf spider's closest living surface-dwelling relative has large eyes, like most types of wolf spider, but the Kaua'i wolf spider has completely lost its eyes because of the realm where it lives in isolation and darkness.
Its favorite prey is another cave-dwelling creature, the Kaua'i cave amphipod, of which only 90 individuals are known to exist.