Earthworms are the world's unsung heros. They loosen and mix up the soil, break down and recycle decaying plant matter and fertilise the soil by bringing nutrients closer to the surface. Birds often rely upon worms as a primary source of food. Because earthworms breathe through their skin, they have to come to the surface when it rains or risk drowning. Famously hermaphroditic, earthworms are both male and female in one body, though it still takes two worms to reproduce. Earthworms range in length from a tiny one millimetre to a massive three metres.

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