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Earthworms, Lowly Answers to Darwin’s Basic Questions

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By Bill Lawyer

I can’t remember the first time I ever dug into the ground in search of earthworms. But as a kid I was always turning over logs or looking in rocky streams to see what kind of strange animals I might encounter.

It wasn’t until I studied earth science in junior high school that I was able to put a name to the many macro-invertebrates I had encountered in the forests and fields.

My grandfather was a farmer with woodlots to manage, and when I visited he pointed out some of the most obvious critters — such things as millipedes, centipedes, ants, crayfish, frogs, toads, salamanders, and the like.

Which brings us to the subject of earthworms. I was assured that earthworms wouldn’t hurt me, but they certainly were not something that I would keep as pets.

When my children were growing up, however, they not only had a chance to find all kinds of critters around Rye’s nature preserves, but they also followed the adventures of the famous “Lowly Worm” in many of Richard Scarry’s children’s books.

Mostly, I learned about earthworms from my friends who fished. I knew that earthworms made good bait and that the best time to find them is at night.

I also knew that if I went out in a spring rain I’d be likely to encounter earthworms inching their way along the sidewalks.

Just a few weeks ago, I saw a whole herd of earthworms moving steadily down my driveway. At first glance I thought they were slender twigs, until I noticed that they were moving. Why?

Well, Dr. Chris Lowe, Lecturer in Waste and Environmental Management, University of Central Lancashire in Preston, UK, has the answer. It’s not what many scientists have thought, that they come out of the ground to avoid drowning.

Research has shown that earthworms can live for several days completely submerged in water. In fact, they breathe through their skin, which has to be moist or they’ll die.

Rather, it’s because being on a paved surface enables them to get to a desirable habitat much more easily. Scientists consider this travel place-to- place is the earthworm’s version of migration. They also migrate vertically from nearly on the surface in summer to much further down in the winter.

But that was only scratching the surface about these under-appreciated invertebrates.

The best example of this can be found in the research and writings of the venerable Charles Darwin. We often think of him as a high-level scientist developing proof of his theory of evolution. But, in fact, Darwin started raising and studying earthworms well before he went on his travels around the world collecting samples and taking notes of the many “exotic” creatures.

There are several reasons Darwin studied worms. First, if evolution is true of finches in the Galapagos, then it must be true of all forms of life. Second, he selected earthworms because they are very easy to handle and manage.

He also proved that while earthworms do not have eyes, they do have sensory organs that can differentiate between light and darkness. He didn’t do this with complex equipment, just simple oil lamps or candles of varying intensity of reflectors. Similarly, he showed that earthworms were deaf, but were sensitive to vibrations created by sound — from a piano, for example.

After many off-and-on continuations of his earthworm studies, Darwin finally decided to publish his findings in 1881. What’s surprising is that his book on the lowly earthworm sold nearly as many copies as the “Origin of Species,” published in 1859. That’s because not only was it a scientific masterpiece of research, but it contained valuable agricultural advice.

In North America, the earthworm continues to be the farmer’s friend, breaking down the soil for planting, and a good creature to find right in our backyard.

With images

Richard Scarry’s much-loved “Lowly Worm”

Painting of Charles Darwin in the 1830s by George Richmond

 

 

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