Last summer, we decided to build a new shop. That meant cleaning out a bunch of old junk in the fence row and digging down to make a foundation. in the process, we disturbed legions of night crawlers (Lumbricus terrestris). They had made their homes in and around all the debris that had been dumped there half a century earlier, and came raging to the surface (really, can a worm rage?) when their homes were destroyed. Fishing, anyone? That’s what I think of when it comes to earthworms. But there’s lots more to them than slimy wiggly fish bait. Bring the robins back.
In fact, they fascinated Charles Darwin for decades. His last book was all about them, titled: “The Formation of Vegetable Mould, Through the Action of Worms (1881). So, what’s the deal?
Somewhere in my elementary school education, I learned that worms eat dirt. And they do. But what they’re after is the organic material in the dirt. They have a tube within a tube structure that allows the dirt to pass from their mouth at the front end, through the alimentary canal, where various stages of processing (including a gizzard for grinding their food) capture whatever organic material is to be had, and then at the end, deposit the castings or leftovers at the back end. This process has major benefits for soil. First, the worms help to break down organic material in the soil, transforming it into humus which frees the nutrients the plants need. Second, the worms aerate the soil, that is loosen it and make space for pockets of air. Plant roots actually need air to function, and the worms help with that. The third benefit, of course, is to the birds and the fisherfolk who use the worms for food and bait.
What I also learned, but which turns out not to be true, is that you can cut a worm in half and have two worms. This is only partly true. If a nightcrawler loses its tail, it can grow another, smaller, less effective one. If it loses its head, it dies. Nightcrawlers do have a primitive brain that coordinates their movements and processes their sensory inputs. Without the brain, it dies.
What they didn’t teach me in elementary school is that these worms are hermaphrodites. That is, they have both male and female sex organs with the sperm producers at the back end, and the egg producer at the front end. Two worms lie next to each other, and line up so that the sperm factory of one worm lines up with the clitellum, a whitish band near the front end of the worm where the eggs are produced., on the other worm. Once they’re lined up, they send packets of sperm over, and the clitellum produces a mucus sheath and nutrients. The worms separate and slide their slick, slimy bodies backward out of the clitellum ring. This sliding process captures the eggs and sperm packets in the ring, and once the worm is out, the ends dry out and seal, creating a cocoon where the eggs are fertilized and embryos develop. When conditions are just right, baby worms hatch, looking like miniatures of their parents. A worm can live from four to six years, and can mate many times a year!
They live in vertical burrows that can be up to six feet deep, and can eat their body weight each day. They’re reddish-brown and covered in a coating of slime that helps them move through the soil. They have a mouth at the front, and above the mouth opening is a fleshy protuberance that can sense the environment and also closes the mouth when the worm is resting. They don’t have eyes, but do have light-sensitive organs that warn them when they’re on the surface. They like to stay where it’s dark and moist. They have segmented bodies that move by contracting some segments and extending others, and they have little hairs on these segments that they can use to anchor themselves and control their movements. And they don’t have lungs—they breath through their skin. Because of this, the skin has to remain moist to allow gas exchange, and if they dry out, they will suffocate and die.
The ground on Owl Acres is full of nightcrawlers. Soon spring will bring the robins back, and they’ll start feasting on the worms as they rise from their winter slumber down below the frost line. All seems to be in balance. But wait—these little “intestines of the earth” as Aristotle is said to have dubbed them, are not native to Owl Acres. They came, like so many other living things, across the ocean, aided by humans, from their native Europe and Asia. So before Europeans settled the prairie around here, what did the robins eat?
Photo by Ryan Hodnett