The threadworm is a parasitic nematode worm of the genus Enterobius (Oxyuris), which lives in the upper part of the human large intestine. The threadlike female worm, some 12 millimeters long, is larger than the make; it emerges from the anus in the evening to deposit its eggs, and later dies. If the eggs are swallowed and reach the intestine they develop directly into adult worms. Threadworms cause enterobiasis, a disease common in children throughout the world.