The term ‘Earthworm’ is a collective name for a group of organisms within the class Oligochaeta which means 'few bristles'. Oligochaeta is a class in the phylum Annelida which means ‘little ring’, these little rings refers to segments found on all Annelids. Earthworms are distinguished from other groups of Oligochaeta by their ecology.
Earthworms are predominantly terrestrial, though they can be found in some freshwater environments such soils of river banks and at the bottom of lakes. Earthworms are found on all continents. Earthworms need a moist environment due to their method of respiration, as they diffuse oxygen and carbon dioxide through their skin. Their skin produces a film of mucous for the process to occur, and therefore has to be moist for respiration to take place.
An Earthworm has a long segmented body, which has a mouth at one end and an anus at the other. The mouth is closer to the clitellum, which is commonly called the saddle, found around a third of the way down the body. An earthworm moves via a line of bristles called setae, which can be found in pairs on each segment.
To find more out about the biology of an earthworm please visit our Earthworm Biology page.