The species commonly known as “pinworms” that causes enterobiasis, a parasitic infestation of the large intestine. The small, white adult worms live in the cecum and adjacent portions of the colon; at night the females migrate to the anus and lay their eggs on the perianal skin. The eggs hatch by morning. Infestations cause irritation of the anal region and allergic reaction of the neighboring skin, accompanied by intense itching, which may result in loss of sleep, excessive irritability, and a secondary infection of the area around the anus as a result of the scratching. Distribution is worldwide.