Pinworm (Enterobius vermicularis). Pinworm is a parasite living in the caecum and it occurs in men. Female individuals are about 1 cm long and 0,4 mm wide. Their rears are transparent and sharpened. Male individuals are several mm long and they can barely be seen with a human eye. The female live for about 4 weeks then they leave the body through the anus. They crawl in the groin skin and dry a minute or so later. The pinworm migration generally takes place in the evening, when people are asleep. Every parasite leaves about 11000 eggs behing while moving. From the majority of eggs invasive larvas are hatched whithin 6 hours. It sometimes happens that the larvas leave their egg shells on the anus skin and come back to large bowel. Generally the invasive eggs get to the same or another host through the mouth or nose. Having left the egg shells, the larvas initially stay in the ileum and grow up in the small bowel.