Waitomo Caves, North Island, New Zealand

You’d better know how to glow if your name is luminosa, or Arachnocampa luminosa to be precise. The light emitting New Zealand glowworm is one of nature’s most marvelous inventions, even though (and ironically), it is easily disturbed by light. That’s why you have to go deep into caves, grottos or dark, damp places in the forest to find them, preferably without your camera or flashlight. The caves of New Zealand’s North Island are great places to see them. The Arachnocampa luminosa is actually a fungus gnat that goes through 4 developmental stages during its lifetime. During three of those the insect has the ability to glow.

Shortly before they die, female adult gnats create nests and attach their eggs to the ceiling of the cave. The eggs hatch and larvae emerge. To feed itself, each larva produces silk and mucous to hang threads (snares) from the dark ceiling of the cave. Like a spider’s web, insects are caught in the snares, retrieved and eaten by the larva. To attract the insects, the larva creates a blueish-green glow in its abdomen, perhaps to fool the insects into believing they are under starry skies.

The larva stage is the longest in the gnat’s life; it will last 6 to 12 months depending on food availability. When the larva pupates, the pupa also glows but this time to attract a mate. Hanging vertically from a short thread, the female pupa glows especially bright, attracting adult male gnats which wait just outside the door for the female adult to emerge. Once she has freed herself from her prison, the female mates with her patient partner and the cycle starts all over again. Adult fungus gnats only live a few days. Their sole purpose in life appears to be reproduction. By the way, adult gnats cannot be caught in the snares. They are too big and can free themselves. 

Our boat is gliding silently through the cave while we are watching in amazement the ceiling lit up like a star-filled sky on a clear night. It is a wonderous and surreal experience. As picture-taking was strictly forbidden inside the cave, I don’t have pictures of my own to show you, but I hope you get an idea of the beauty of this place.