Earthworms are classified under 16 families, which include: Ocnerodrilidae, Sparganophilidae, Ailoscolidae, Almidae, Lumbricidae, Lutodrilidae, Exxidae, Eudrilidae, Glossoscolecidae, Octochaetidae, Hormogastridae, Microchaetidae, Acanthodrilidae, Criodrilidae, Alluroididae, and Megascolecidae.
Generally, earthworms are classified based on their different ecotypes or ecophysiological categories, which include the following:
- Compost earthworms: These earthworms are mostly found in compost areas, or in places with an abundance of rotting plants.
- Epigeic earthworms: These earthworms are found in rotting logs and leaf litter, and they consume partially decayed organic material.
- Anecic earthworms: These earthworms are notable for their ability to pull decaying matter into their burrows.
- Endogeic earthworms: These earthworms consume soil that is rich in organic matter.
The examples of earthworms studied in this section are drawn from these ecotypes.