From: Star Trek: The Next Generation
Caption: A holographic outline of a Tarchannen.
Planet: Tarchannen III. Non-sentient humanoid race, frightened by normal light and visitors who are visible to humanoid eyes only under ultraviolet light. Their species propagated by using a DNA strand implant in an alien host's thymus to reproduce via genetic metamorphosis, which can take years to gestate. The onset of symptoms can vary in time from days to only an hour.