From: Star Trek: The Motion Picture
Caption: Ilia, a Deltan
This usually bald species hails from Delta IV, and is known for being highly developed in the arena of sexuality. In fact, Deltans in Starfleet are required to to take an Oath of Celibacy, so that they do not take advantage of less sexually advanced species. Enterprise navigator Ilia, who was killed by a probe from V'Ger, was a Deltan. Another served on the bridge crew of Captain Styles on the original U.S.S. Excelsior. The Delta IV delegation also has a seat at the Federation Council along with other UFP members.