Earthworms cannot stand dry conditions in the soil: their bodies must always be in contact with damp earth and even a few minutes’ exposure to the sunlight makes them dry up and die.
Earthworms spend most of their lives digging tunnels in the soil. It is quite surprising how they can burrow their way into even hard ground simply by using the strength of their muscles, for earthworms do not have any special physical equipment for digging.
They contract and expand in a rhythmic manner to force an aperture in the ground and then they push on with their head.
The earthworm then expels the ‘digested’ soil and leaves it as a worm-cast. It has been estimated that the yearly deposition above ground of soil by earthworms is between 7 and 16 tons per acre in England. Earthworms can grow up to 15 centimetres or more in length. In tropical countries some earthworms are as long as 2 metres.
Picture Credit : Google