Creepy Critters: An Earthworm’s Secret Weapon

The earthworm found by Trond Larsen in Papua New Guinea, with his field assistant, Danil, in the background. (© CI/Photo by Trond Larsen)

Editor’s note: At CI, we’re dedicated to the protection of all life on Earth, recognizing that all species play a role in the healthy ecosystems that sustain us. However, even we’ll admit that some of them are less … cuddly … than others. In honor of Halloween, we asked CI scientists to recollect on some of their most harrowing wildlife encounters. Here is entomologist Trond Larsen’s story.

The dense fog thickened and swirled, trapping me like the caterpillar of a moth inside its white cocoon. Gaping out of the fog, the maw of a carnivorous pitcher plant hung expectantly from the nearby trunk of a palm-like pandanus tree. I warily picked my way around the tree, along a trail so narrow it permitted only one foot at a time between slick, gnarled roots. On either side of the knife-edge ridge, the mountain plummeted away into the clouds below.

I had been hiking all day through the rugged Saruwaged Mountains of Papua New Guinea’s Huon Peninsula, hundreds of miles from the nearest road. It had been over an hour since I had last seen Danil, my field assistant from the nearby village and only human companion. The grueling walk had already ascended and descended over 1,500 meters (4,921 feet) in elevation. With each step, pain seared through my knee where I had torn the ACL and PCL ligaments a week earlier. My clothes clung chillingly to my skin, waterlogged with sweat and rain.

I glanced down at my feet and saw a whirling, gyrating mass of brown tentacles. About 40 leeches, known by locals as ‘rubber snakes,’ stretched spastically in search of blood. It was hard to imagine that my bright red socks had been white only a few hours earlier. As I paused momentarily to pluck three leeches from my waist, five more grabbed onto my shoes from nearby.

In the trail ahead, I was startled to see a conspicuously yellow, bulbous shape protruding from a thick layer of sphagnum moss. As any naturalist would, I immediately grabbed the protruding end and began to pull. Eight inches later, I held a gigantic, writhing earthworm in my hand. All biologists are aware that brightly colored creatures are often well defended against attackers, a phenomenon known as aposematism. I had a pretty good sense that eating the worm would be a bad idea — but little did I know what was in store for me.

Mucilaginous slime began to flow from the worm, coating its already sticky body in an ooze presumably designed to repel predators. Confident and undeterred, I was curious to examine the unknown worm more closely, and brought it towards my face. In the same instant, fine jets of liquid shot out in all directions from multiple pores along the worm’s body. Burning pain hit my eyes, and I was temporarily blinded. Shocked, I dropped the worm to the ground and rubbed the noxious spray from my reddened eyes and face.


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Danil rounded the corner behind me and found me stooped over. Taking in the scene, he exclaimed, “Oh no, the yellow worm is very bad. It gives you bad sores.” Suddenly less worried about my now recovering eyesight, I began to wonder if my whole face would soon erupt into blisters. Thankfully, Danil went on to explain that the poisonous spray only hurts when it gets into cuts or mucous membranes. Nonetheless, when I asked him to hold the worm for a photograph, he begrudgingly accepted only when the worm was held as far away as possible on the end of a stick.

Part of the excitement of being a tropical ecologist is that you see and learn new things every day in the field. It turns out my ignorance in this case was justified; this earthworm species appears to be new to science, and the toxic spraying behavior has not been described in the scientific literature.

Despite the breadth of indigenous knowledge around the world, scientists still know relatively little about the world around us. So the next time you come upon a yellow worm, or any brightly colored critter for that matter, approach with caution. And consider safety goggles.

Trond Larsen is a research scientist in CI’s Science and Knowledge division. Check out more tales of creepy critter encounters.

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