Earthworm

Earthworms are not insects but segmented worms belonging to the phylum Annelida. Scientists have described more than 7,000 species, living in soils on every continent except Antarctica. Their long, flexible bodies are divided into many ring-like segments and are covered with tiny bristles called setae, which help them grip the soil as they move. Because earthworms breathe through their moist skin, they must remain in damp environments to survive.

Most feed by swallowing soil mixed with dead leaves, roots, fungi, and other decaying organic matter. As this material passes through their digestive system, nutrients are broken down and returned to the soil in a form that plants can use more easily. Different species occupy different depths, with some living near the surface while others dig deep, permanent burrows. Earthworms play a vital role in maintaining healthy soils.

As they tunnel, they loosen and aerate the ground, allowing water, oxygen, and plant roots to penetrate more easily. Their castings, which are the material they excrete after digestion, enrich the soil with nutrients and beneficial microorganisms. Most earthworms are hermaphrodites, meaning each individual has both male and female reproductive organs, although they usually mate with another worm to exchange sperm before producing cocoons containing fertilized eggs.

Earthworms are also an important food source for birds, mammals, amphibians, reptiles, and many invertebrates. Healthy earthworm populations are often considered a sign of fertile, living soil, while pollution, intensive farming, and prolonged drought can reduce their numbers and affect soil quality.