Eggs may contain a developing embryo or a fully developed pinworm larva.

The small size and colourlessness of the eggs make them invisible to the naked eye, except in barely visible clumps of thousands of eggs. The eggs measure 50 to 60 μm by 20 to 30 μm, and have a thick shell flattened on one side. The eggs are translucent and have a surface that adheres to objects. The adult male is considerably smaller, measuring 2 to 5 mm long and 0.2 mm thick, and has a curved posterior end. The adult female has a sharply pointed posterior end, is 8 to 13 mm long, and 0.5 mm thick. Morphology Two female pinworms next to a ruler: The markings are 1 mm apart. gregorii is considered clinically identical to E. Regardless of its status as a distinct species, E. (2003) consider the evidence to be insufficient, and Hasegawa et al. Its existence is controversial, however Totkova et al. vermicularis, and has a slightly smaller spicule (i.e., sexual organ). Hugot (1983) claims another species affects humans, Enterobius gregorii, which is supposedly a sister species of E. Chimpanzees are host to Enterobius anthropopitheci, which is morphologically distinguishable from the human pinworm. Humans are hosts only to Enterobius vermicularis (formerly Oxyurias vermicularis). The pinworm (genus Enterobius) is a type of roundworm (nematode), and three species of pinworm have been identified with certainty. In British usage, however, pinworm refers to Strongyloides, while Enterobius is called threadworm. Throughout this article, the word 'pinworm' refers to Enterobius. Enterobius gregorii, another human species is morphologically indistinguishable from Enterobius vermicularis except the spicule size. Humans are the only natural host of Enterobius vermicularis. Enterobius vermicularis is common in human children and transmitted via the faecal-oral route. Other species seen in primates include Enterobius buckleyi in Orangutan and Enterobius anthropopitheci in chimpanzee. Other than human, Enterobius vermicularis were reported from bonnet macaque. The medical condition associated with pinworm infestation is known as pinworm infection ( enterobiasis) (a type of helminthiasis) or less precisely as oxyuriasis in reference to the family Oxyuridae. It is a nematode (roundworm) and a common intestinal parasite or helminth, especially in humans. The pinworm ( species Enterobius vermicularis), also known as threadworm (in the United Kingdom, Australia and New Zealand) or seatworm, is a parasitic worm. Enterobius vermicularis ( Linnaeus, 1758) (human pinworm).Enterobius interlabiata Sandosham, 1950.Enterobius gregorii (Hugot, 1983) (disputed).Enterobius callithricis Solomon, 1932.Enterobius brevicauda Sandosham, 1950.Enterobius anthropopitheci (Gedoelst, 1916) (chimpanzee pinworm).

Pinworms (U.S.)/Threadworms (U.K.) ( Enterobius vermicularis) For the genus of nematodes, see Oxyuris (nematode).

Pooping pin worms