When the ground is flooded by heavy rain, worms come to the surface because now they are too moist. The water surrounding the worm blocks (breathing) the emission of carbon dioxide through the worm's skin. The worm's body retains this gas. Thus the worms surfaces to release that gas by breathing.
Worms live in burrows underground. The burrows are created as the worm moves its muscular mucus coated body through the soil. Worms eat leaves, both decayed and fresh, and assorted plant material. They ingest soil too.
The gut, or food tube, runs from the mouth to the anus. The mouth of the worm has no teeth or jaws, it sucks in food and dirt. The material goes through the esophagus to the crop. Next stop is the gizzard where tiny stones in the soil work to grind the food. Then the material goes to the intestine where digested food goes into the blood stream and non digested material exits via the anus.
Worm poop, or castings, is beneficial to the soil thanks to minerals and improved texture brought about by worm processing.
The pointed end of the worm is the beginning, or head (left, in photo below). The thick band about 1/3 of the way down the worm is the saddle, or clitellum. The end of the worm (right, in photo below) is where the anus is located.
The outer body is made up of segments, or rings. Muscles run all along the worm under the segments. Outside of each segment are bristles made of chitin (the same stuff that makes up the exoskeleton of insects). These bristles are like little appendages. Indeed, if you have ever tried to pull a worm out of the ground and found it hard to do, it's because the worm was gripping the earth with those bristles. Sometimes worms get pulled apart during these battles. The worm can survive and regrow part of its body if not too much is lost.
The worm is a red blooded creature. Five sets of blood vessels are each run by a simple heart.
Worms are hermaphrodites. They exchange sperm to fertilize their eggs. Two worms lie side by side their seminal vesicles (located near the head) pressed against their clitellums. The sperm fertilizes the eggs stored in the clitellum. The fertilized eggs are cocooned and left in the warm soil. The baby worms hatch in 60-90 days.
The life span of a wild earthworm is about 2 years.