Abstract
A re-examination of the life-cycle of the mouse pinworm, Aspiculuris tetraptera has shown that the infective eggs hatch in the lower intestine or in the caecum of the host, to release the first stage larvae. After moulting, these larvae migrate into the crypts of the colon; those larvae which do not migrate into the crypts apparently pass out of the host with the faeces. The larvae in the crypts, presumably the third stage, later return to the lumen of the colon where they mature into adults. Males are mature by about the 20th day and females by the 23rd day. Viable eggs are released by the females 24 days after infection.