The Dopterians are a humanoid race who possess a similar brain structure to the Ferengi and, like them, are unreadable by telepaths such as Betazoids. In appearance their bald heads are covered with a slight mottling, and they have a Ferengi-like nose, a Lissepian-like extended cranium, and a ridge from the rear of the head to the stubby, pointed earflaps.
Constable Odo correctly concluded that a Dopterian pickpocket was responsible for the theft of Ambassador Lwaxana Troi's latinum hair brooch aboard Deep Space 9 in 2370, since she was unable to discern any emotions of guilt in her surroundings. (DS9: "The Forsaken") The USS Enterprise-D crew encountered a Dopterian named Gorta the same year, who was a discarded accomplice of the Duras sisters. (TNG: "Firstborn")