Answer/Explanation:
Nocturnal ⇒ occurring or active at night
Reason 1; During the day earthworms mostly stay in their burrows underground
Reason 2; At night they come up on to the surface to feed
Knowing that; They have receptor cells in their skin that are sensitive to light and touch. Worms breathe through their skin. It's imperative for them to stay cool and moist in order to continue breathing. If they came out during the day the sun would dry them out and they would not be able to breathe.
~Lenvy~