It is pointed out that the role of electrons in dynamics pair ion and negative positive plasmas cannot be neglected even at extremely low density electrons, i.e., ne0n+0≪mem+ (where nj0 background jth species mj mass particles j-species while j = e, +, −) because electron thermal velocity almost always larger than velocities ions, vT± ≪ vTe. An analysis electrostatic waves unmagnetized (NPIE) (...