Fig. 1. Life cycle of Enterobius vermicularis. 1a/b Whitish adult males (1a: 2–5 × 0.6 mm) and females (1b: 8–13 mm in length) live in the colon and rectum of man (especially children). 2/3 After copulation females migrate (at night) through the anus onto the perianal region, lay numerous (10 000) eggs and die. 4 Eggs embryonate within 6 h, forming the infectious first larval stage. 5 These eggs may be swallowed, or hatched larvae may enter the intestine directly via the anus, or erroneously via the vagina of women. 6 Inside the intestine the life cycle is completed within 4–6 weeks, leading to mature adults inside the colon. ES, esophagus; L, larva; TE, testis; UT, uterus; V, vulva