Huge Millipedes, Old Crayfish Show Weird Evolution of Cave Life

Avid cavers aside, most humans tend to think of caves as dark, damp and dangerous. But to a host of animals, caves are actually quite hospitable.

Though some cave denizens arrive accidentally, perhaps swept underground by water flowing into a sinkhole or through a crack in a creek bed, most seek out caves as protective havens from the elements and predators; some have evolved over millennia to exploit a previously unoccupied niche.