Pulsationally stable (small dots) and unstable (circles) modes in n–log T_e plane for models along the evolutionary track of a M = 1.8 M_ȯ star. n is the radial order of oscillation and T_e is the effective temperature of the stellar model. Panel (a): the anisotropic equilibrium model; Panels (b)–(f): the quasi-anisotropic models with parameters given in Table 1, see the text for details.