The Tarlac were one of two primitive races, the other being the Ellora, that were conquered by the Son’a in 2325. By 2375, both the Tarlac and the Ellora were fully integrated into the Son’a society as indentured servants. (Star Trek: Insurrection).
A Tarlac also appeared in Star Trek: Voyager but that was a special case.
All the Tarlacs were played by uncredited performers.
Michael Westmore was the makeup designer for both Star Trek: Insurrection and Star Trek: Voyager. Scott Wheeler worked on the Tarlac in Insurrection.
Star Trek: Voyager: ‘Life Line’ (1999): When the Doctor’s initial attempt to help his creator, Dr Zimmerman, is rebuffed he tries again, changing his holographic appearance to that of a Tarlac.
Star Trek: Insurrection (1998): Several Tarlac nurses served aboard Ru’afo's flagship in 2375. They assisted in the process of skin streching in the laboratory aboard the ship.