Lumbricus terrestrius, the common earthworm is also known as the Rain Worm and Dew Worm, because it is often found on the surface after a rain or on a dewey morning. This worm can breath for quite a while under water, but it needs to come to the surface to mate. They die quickly if their skin dries out, or if they are exposed to the ultraviolet light of sun light, so rainy days are the perfect time to search for a mate. While they can breath under water, they can't eat or burrow there, so they starve quickly if trapped in a puddle.