The lugworm lives in muddy sand. It builds a U-shaped burrow that is strengthened with a lining of mucus, with two openings at the surface. The worm draws sand into the burrow through one of the openings. After it digests any food it finds in the sand, and then ejects the sand through the other opening. When the tide is low, the evidence that lugworms have been at work digesting food is seen by piles of mud.