Adult Annelid earthworms range from less than 1/2 inch long to a record-breaking 22 feet in length. One giant earthworm species averages 54 inches.
Annelid earthworms have three body regions made up of little rings called segments. Each segment is divided from the others by an internal septa and consists of a fluid-filled cavity called a coelom.
Most Annelid earthworms are red, brown or pink. Bluish-colored earthworms live in the Philippines, while the United Kingdom is home to a green earthworm species.
Earthworms lay eggs within a tiny, hard cocoon. Eggs hatch as quickly as two weeks in warm weather and as long as three months in cold weather.
Earthworm bodies are covered with chemoreceptors, which are minute-sense organs. Annelid earthworms use chemoreceptors to sense chemicals in the soil and to taste their food.
More than 1 million earthworms can live in one acre of land. Charles Darwin studied earthworms for about 39 years.