World of Wonders

When we see things that aren’t, we miss the wonderful things that are.

The Cave Glow Worm

In dark rocky caverns, the cave glow worm catches insects the way an angler catches fish. The worm hangs dozens of silk threads from the cave ceiling like fishing lines from a boat. The threads can be up to 20 inches long, and are covered with droplets of the worm’s sticky mucous. When an insect flies too close, it’s caught by the line. The worm reels in its catch and enjoys its meal.

Like an angler, the cave worm attracts its prey with a lure. In an organ in its tail, a chemical reaction creates light that can easily be seen in the pitch darkness underground. Flies, mosquitoes and moths see the glow and fly toward it. In some caves, the light of thousands of worms makes the cave ceiling look like a starry night sky.

The cave glow worm (g. arachnocampa) is found mostly in New Zealand and Australia. The worm is actually the larva of a small, gnat-like fly. After nine months of catching prey and growing to over an inch in length, the larva becomes a pupa. Hanging by a strand of silk, the pupa wraps itself in a cocoon. Inside its silky hideaway, it magically transforms into an adult fly.

The female fly also glows, but she’s not trying to attract a meal. In fact, adult flies only live a day or two and don’t eat at all. The female adult uses light to attract a mate. Males wait patiently beside glowing cocoons until the female emerges. After the two flies mate, the female will lay her eggs–and the cycle begins again.

(From a recent project for young readers, about creatures that have evolved bioluminescence.)


Filed under: nature,

About me

I am a Toronto-based writer, author and photographer who is inspired and fascinated by science. Science is our best way of understanding the natural world, but it is much more than that. Science is culture, and its pursuit ultimately leads to meaning, values and wonder.  My interests include evolution, Darwin, the Galapagos Islands, secular humanism, religion, skepticism, climate change, and science culture.  For many years, I wrote and produced astronomy programs for the McLaughlin Planetarium of the Royal Ontario Museum. I am author of many books for young readers (Sterling Publishing and Penguin Young Readers, N.Y.) and articles for children's magazines. I also write non-fiction related to the themes reflected in this blog. You can read some of my longer non-fiction and view my photographs at, and follow me at


%d bloggers like this: