Linnaeus recognized only one species of earthworm and named it Lumbricus terrestris.
During the winter earwigs lie dormant; but in the early months of the year females with their eggs may be found in the soil, frequently in deserted earthworm burrows.
In Benhamia caecifera and at least one other earthworm there are numerous caeca, one pair to each segment.
The earthworms of England belong entirely to the three genera Lumbricus, Allolobophora and Allurus, which are further subdivided by some systematists; and these genera form the prevalent earthworm fauna of the Palaearctic region and are also very numerous in the Nearctic region.
There is a definite Annelid group (see Annelida), including the Archiannelida, the bristleworms (see Chaetopoda), of which the earthworm (q.v.) is the most familiar type, the Myzostomida, Hirudinea (see Leech) and the armed Gephyreans (see Echiuroidea).
In the development of the Acanthodrilid earthworm Octochaetus (F.