Wonderful Worms

There have been quite a few wet and cloudy mornings of late. On one such morning I was hurrying to work down the sidewalk between the school gym and the basketball court. I suddenly halted mid-stride and stared at an earthworm lying in my path. I looked at it as though I had never seen such an amazing creature before. For the past few weeks, I had been reading about worms in preparation for setting up 18 classroom worm bins at Mountain School. We had received a grant from the Los Alamos Public Schools Foundation to implement hands-on science lessons related to worms. So while I had read a lot, I hadn't actually seen a live worm in quite a while. I stood in the September mist transfixed as I reflected back on Amy Stewart's fascinating book The Earth Moved, On the Remarkable Achievements of Earthworms. Where was this worm's burrow and why did it travel across concrete and asphalt so far from the soft earth? Was it an endogeic, anecic, or epigeic species? Did it hear me or know I was there? How much soil had this one worm turned?

In her book, Amy Stewart weaves the work of today's oligochaetologists, scientists who study worms, with the historic story of Charles Darwin's final publication, The Formation of Vegetable Mold Through the Action of Worms, with Observations on Their Habits. It was another of Darwin's "groundbreaking" books. Until Darwin, scientists hadn't taken much interest in life underground and considered earthworms pests. As Darwin, "understood that tiny incremental changes in the environment can bring about the evolution of a species," he also understood, "that soil could over time, be transformed through the efforts of earthworms" (Stewart, 2004).

Darwin studied a worm called Lumbricus terrestris, the nightcrawler, which was most likely the worm that I had found on the sidewalk. It was reddish-brown along its dorsal side and light almost translucent underneath. The nightcrawler is classified as a deep soil or anecic worm and can live up to six years. As it tunnels through the soil, it eats decaying material along with a little soil to help with the function of its gizzard. Its vertical burrow can be an amazing eight feet deep where it stays during dry or cold periods. At night, they emerge in search of food, pulling small leaves and twigs into their burrows. At the entrance to their burrows are small piles of castings, or worm manure, that they leave behind. It is through their work that these small soft –bodied animals plough through the hardest and poorest dirt and turn it into rich fertile soil for new life.

Darwin had many questions about earthworms, which he tested with simple experiments. No small detail went unnoticed by Darwin. For example, he wanted to test whether worms made decisions about which end of a leaf to pull into their burrows. So Darwin went outside in the early mornings and carefully pulled leaves out of worm burrows to find out the answer. After checking 227 burrows, he found that 181 of them had leaves pulled in by their apex. Of course he was still curious and he designed more experiments to test the habits of his worms. Maybe you would like to try one of Darwin's worm experiments. Darwin wanted to know if worms could hear so he tested their reaction to quiet and loud noises. He found that his worms didn't behave differently around loud noises. Do you get the same results? As a second experiment, Darwin tested his worms' reactions to vibrations. He set his flowerpots of worms on top of a piano so they could feel the vibrations of the notes. Guess what the worms did when the C note was struck? They disappeared into their burrows. How do you think sensitivity to vibrations would help the earthworm survive? Darwin took good care of his worms and kept them in flowerpots filled will slightly damp soil. He kept them from freezing and fed them leaves. If you experiment with worms, be sure to take care of them too. Be curious and have fun.