Glowworms in Blue Mountains National Park, Australia

Subterranean stargazing. Glowworm caves in Australia

Down under the land in the Land Down Under, cave explorers may find these subterranean spaces illuminated by an unlikely light source. Fungus gnat larvae—more affectionately known as glowworms—speckle the walls and ceilings of caverns here in Australia during the warm season, from December to March.

To humans they're hypnotizingly harmless and add a little otherworldly charm to the caves in such places as Blue Mountains National Park, as seen in our photo. But if you're a fly or mosquito, beware! Glowworms dangle tiny, sticky silk strands that ensnare winged insects flying toward what looks like a starry night sky, but is in fact the cave ceiling, covered in glowworms, patiently waiting to reel in a deceived bug.