Earthworms do not live in deserts or regions where there is permafrost or permanent snow and ice. Typically only a few inches (7 or 8 centimeters) long, some members of this species have been known to grow to a snakelike 14 inches (35 centimeters).

Earthworms' bodies are made up of ringlike segments called annuli. These segments are covered in setae, or small bristles, which the worm uses to move and burrow. These terrestrial worms typically dwell in soil and moist leaf litter. Their bodies are characterized by a "tube within a tube" construction, with an outer muscular body wall surrounding a digestive tract that begins with the mouth in the first segment. As they burrow, they consume soil, extracting nutrients from decomposing organic matter like leaves and roots.

Earthworms are vital to soil health and to plants growing in it because they transport nutrients and minerals from below to the surface via their waste. An earthworm can eat up to a third of its body weight in a day.

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