These worms are creamy pink and have minute fleshy projections called parapodia which function during movement and respiration. Another distinguishing feature of these creatures is their large eversible proboscis which is armed with four poisonous jaws. Many a careless worm digger or fisherman has felt their painful bite. A bloodworm's body can grow to be fifteen inches in length and be three-eighth inches in diameter. Their growth is dependent upon diet, temperature and salinity.
Bloodworms are most abundant in the middle portion of the tidal flats.
They feed on marine worms, mollusks and other invertebrates while burrowing through mud or sand. In comparison to some other polychaetes, bloodworms are poor swimmers. However, they are excellent burrowers using their conical prostomium or lip, stiff parapodia, and peristaltic motion. Bloodworms sense through the use of tactile cells which are primarily located in their head area. An anterior brain receives impulses from a large ventral nerve cord, that runs from the anterior to the posterior end of the worm.