Earthworm (Lumbricus terrestris and relatives)

InvertebrateAnnelidSoil engineer

Overview

Earthworms are segmented worms — annelids — that live in soil and rank among the most important animals in land ecosystems, despite being rarely seen. The common earthworm (Lumbricus terrestris) is a familiar reference species. An earthworm's body is built from many similar ring-like segments, with a smooth, often paler band (the clitellum) toward the front that has a role in reproduction.

By burrowing, feeding, and producing nutrient-rich castings, earthworms mix, aerate, and enrich the soil — work so significant that Charles Darwin devoted a whole book to it.

Note: “earthworm” covers many species worldwide; some are introduced outside their native ranges, where their effects on soils and forests can be mixed. Treat general statements accordingly and verify specifics.

Habitat & Range

Earthworms live in soils across much of the world, from gardens, grasslands, and farmland to forests, wherever the ground is moist enough and contains organic matter. Different species occupy different soil layers — from surface leaf litter to deep vertical burrows.

Diet

Earthworms feed on dead and decaying organic matter — leaves, roots, and other plant material — along with the microbes and fine particles in soil. They draw food into their burrows and pass soil through their gut, extracting nutrients and leaving behind nutrient-rich castings that enrich the earth.

Behavior

Earthworms move by waves of muscle contraction, gripping the soil with tiny bristles (setae) on each segment. They breathe through their moist skin, which is why they need damp conditions and may come to the surface after heavy rain. Earthworms are hermaphrodites — each has both male and female organs — but two worms still pair up to exchange sperm, after which the clitellum forms a cocoon that holds the developing eggs.

Human Interaction & Conservation

Earthworms are hugely beneficial to gardening and agriculture: their burrowing aerates soil and improves drainage, and their castings boost fertility, which is why they are valued in composting (vermiculture) and as indicators of healthy soil. In some regions, however, introduced earthworms can alter native forest soils, so their role is not universally positive. Consult authoritative sources for specifics.

More photos of the earthworm