Earthworm is a metamerrically segmented animal. There are about 500 species of pheretima and 13 of them are found in India.
Phylum – Annelida
Class – Oligochaeta
Genus – Pheretima
Species – Posthuma
Earthworms live in a moist soil rich in dead organic matter or humus. They are abundantly found in old pastures, lawns and gardens. They live in a burrows and the burrows are flooded with water in rainy season; they leave the burrows and creep on the moist surface of the soil in order to respire in air.
The earthworm is nocturnal animal. During day time is lies passive in the burrow. The earthworm comes out of burrow during rainy season only when the burrows are flooded with rain.
(i) Burrowing: The earthworm makes its burrow by simply pushing the body through the soil if it is soft and by eating soil, if it is hard. Tentrance of the burrow is often covered with faccal castings, pebbles or leaves to keep away water and enemies. Walls of the burrow are cemented that slime secreted by skin glands to prevent their collapsing.
(ii) Feeding: the main food of earth worm is decaying organic matters of the soil. The worm takes food by sucking action. The organic matter is digested and absorbed in the alimentary canal and the residual matter is passed out as small pills called worm-castings. The worm casting appears as small heaps in the fields and gar dens during rainy season.
Earthworm breeds in the rainy season. It is hermaphrodite. During copulation mutual exchange of spermatozoa occurs between two worms. It occurs at night. Several spermatozoa these eggs are packed into an egg case or otheca. Oothecae are deposited just below the surface of the soil. Only one worm develops in the ootheca.
(iii) Regeneration: The earthworm possesses a good power of regeneration.