HR diagram showing the location of Am stars. The filled circles are the Am stars which were found to pulsate, while the open circles are the Am stars which were not found to pulsate. The solid lines indicate the location of the ZAMS and the fundamental radial mode red and blue edges of the instability strip (Dupret et al. 2005). The large cross indicates the typical uncertainties in log T_eff and log L. The dots are the δ Sct stars from the catalogue of Rodríguez et al. (2000).