Eggs are deposited at night by the gravid females.
Eggs are ingested via person-to-person transmission through the handling of contaminated surfaces (such as clothing, linen, curtains, and carpeting), or airbourne eggs may be inhaled and swallowed. Self-infection may also occur if eggs are transferred from to the mouth by fingers that have scratched the perianal area.
After ingestion, larvae hatch from the eggs in the small intestine. The adults then migrate to the colon. The life span of the adults is about two months. Adults mate in the colon, and the males die after mating.
Gravid females migrate nocturnally to the anus and ovideposit eggs in the perianal area. The females die after laying their eggs. The time period from ingestion of infective eggs to the ovideposition of eggs by females is approximately one month.
The larvae develop and the eggs become infection within 4-6 hours. Newly hatched larvae may also migrate back into the anus, and this is known as retroinfection.
Diagram from http://www.drnatura.com/parasites.html#Enterobiasis