Some scientists estimate that there are approximately 50,000 earthworms per acre of moist soil. Earthworms live in deep, dark, long, and narrow tunnels or burrows under the ground, They cannot tolerate heat and sun and so during the summer they come up to the surface only at night. They also leave their burrows when it rains because it is easier for them to move on the wet surface. After a rain you will notice multitudes of earthworms on the surface. The wet ground allows them to move without drying out. In this way, earthworms have helped produce the fertile humus that covers the land. As a result the layers of soil are thoroughly mixed, seeds are covered and enabled to germinate, and over long periods of time stones and other objects on the surface are buried. This process has even buried and preserved ancient buildings. Each year earthworm castings cover each acre with as as much as 18 tons of rich soil.When earthworms die, usually in the dry summer, the organic material making up their bodies is gradually released providing additional nutrients for plants.

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