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The Dirt on Soil Down & Dirty Field Guide Soil Safari

Night Crawler Night crawler
Lumbricus terrestris

Vital Statistics:
Length:9-30 cm (would fit in your hand).
Lifespan:3-6 years
Total Earthworm Population:up to 300 per square meter (several in each shovel of soil).

Natural History:
Our largest and most common species of earthworm is not native to North America. Night crawlers stowed away with European settlers bringing their favorite plants. Since then they've spread everywhere people have gone.

Earthworms have no teeth. That doesn't stop them from eating just about any dead organic matter they come across. They also swallow soil as they burrow. The microscopic animals in each bite of soil become worm food, too. An earthworm's gut is a great place for bacteria to grow. Earthworm castings add more bacteria back to the soil than the worm eats. More bacteria mean healthier soil. Together, all the worms in an area the size of a football field can eat about four tons of earth a year! All this adds to the humus in the soil.

It's a myth that earthworms come to the surface when it rains because they are drowning. Some scientists think that this behavior helps worms migrate to new territory or to find a mate. But no one knows for sure why they do it.

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Pictures: Saskatchewan Interactive/Dr. Jeff Bettany | Point Pelee National Park, Canada |
Jon C. Glase Ph.D.

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