We've unearthed eight earthwormy facts:

  1. Most worms are very small, but there can be as many as 1 million per acre.

  2. Tunnelling earthworms let air into soil. This allows plant roots to grow more easily. Aerated soil also absorbs water more easily, reducing the risk of soil erosion.

  3. Worms expel what they eat as casts. Casts look like spaghetti mounds. They are higher in essential plant nutrients (like potassium) than ordinary topsoil.

  4. Worms can regenerate. But a worm chopped in half will not re-grow into two worms. Usually it's only the head end that lives on.

  5. Worms were one of the first multi-cellular animals to evolve. Fossil casts have been found dating back more than 600 million years. That's 300 million years before the dinosaurs.

  6. There are more than 1,800 species of earthworms in the world. The African giant earthworm can grow to 7 metres (22 feet).

  7. Worms cannot see or hear. They have between one and five pairs of hearts and are mostly muscle. Pound for pound they can be 1,000 times stronger than the strongest man.

  8. Want to compost your kitchen waste but don't have a garden? Try an indoor worm bin. The nutritionally-loaded worm casts can then be used as soil.

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