A cave of glowworms

It has been quite some time since we linked out to an Ed Yong story, and title notwithstanding this is as good as they come:

The Most Beautiful Death Trap

The ethereal allure of a cave full of glowworms masks a sinister purpose and a weird origin story.

At first, they look like stars. I see them as I gaze upward at the ceiling of a flooded, pitch-black cave—hundreds of blue pinpricks. As my eyes habituate to the darkness, more and more of them resolve, and I see that they are brighter and more densely packed than any starry field. And unlike the night sky, these lights don’t appear as a flat canvas, but as a textured one. Some are clearly closer to us than others and they move relative to each other, so the whole tableau seems to undulate gently as our boat sails beneath it. These lights are not astrological, but entomological. They are produced by insects called glowworms.

The word “glowworm” is sometimes used colloquially to describe fireflies and click beetles. The insects in the caves aren’t part of either group. They’re maggots—the larvae of small flies called fungus gnats. Hatching out of eggs that are laid on the ceilings of caves, the larvae spin hammocks of silk. From these hammocks, they lower up to 70 threads of silk—extremely strong, and coated with blobs of sticky mucus. These threads, which dangle downward like bead curtains, are traps, and the glowworms bait them by triggering a chemical reaction in their rear ends that emits blue light. The light lures in other insects that get entangled in the silk, and are eventually reeled in and devoured by the glowworms.

After 6 to 12 months of eating whatever they can ensnare, the larvae transform into adults, which lack mouths and never eat. Their only job, in the final few days of their lives, is to mate and create the next generation of glowing-bottomed, trap making juveniles.

These luminous insects are found in the dark and damp corners of New Zealand and Australia, and the Māori know them as “titiwai”—a word that refers to light reflected in water. That etymology reflects the glowworms’ habit of inhabiting damp and dark places, including riverbanks, tropical rain forests, and—most famously—caves like those at Waitomo. For thousands of tourists, these places are major attractions, where one can gaze at the ethereal beauty of a living, indoor star field. But for the thousands of moths, midges, and mayflies flitting around in the darkness, these are places of death…

Read the whole article here.