Enterobius vermicularis

Enterobius vermicularis. Immature female pinworm (unstained, scanning power). This larva was recovered from the feces of a patient who had colitis. Its size and morphology indicate that it had been developing in the body for approximately 2 to 3 weeks. Note the absence of the anterior cephalic inflations and reproductive organs. The typical pinworm esophagus is apparent with the muscular and bulbous portions separated by a narrow isthmus. At the posterior end the pointed tail is separated from loose cuticle, which indicates that this worm is in the process of molting to the adult stage. Immature worms are rarely seen either in feces or in cellulose tape preparations.