What is the external landmark on an earthworm?

The external landmark on an earthworm is the clitellum, a thickened, glandular band found near the anterior (front) end of the worm. It plays a crucial role in reproduction by secreting a cocoon for eggs during mating. The clitellum is usually more prominent and lighter in color than the surrounding segments, making it easily identifiable. Other external features include segments and setae, small bristle-like structures that aid in movement.