Sequoia National Park, Calif. ? Twenty-seven previously unknown species of spiders, centipedes, scorpion-like creatures and other animals have been discovered in the dark, damp caves beneath two national parks in the Sierra Nevada, biologists say.

The discoveries included a relative of the pill bug so translucent that its internal organs are visible, particularly its long, bright yellow liver. There was also a daddy long legs with jaws bigger than its body, and a tiny fluorescent orange spider.

While it is extremely rare to find new mammal or bird species on the surface, caves still hold an abundance of secrets. Like the deep sea, they are often difficult to reach and seldom explored.