Also with sufficiently high mass loss the blue loops do not emerge at all. We will not discuss effects of mass loss anymore in this paper because they do not change any qualitative results presented here. Despite this it has to be remembered that it is a common phenomenon and it should be enabled during construction of detailed asteroseismic models.

The bottom-left panel depicts the instability areas calculated for higher value of convective overshooting, $f=0.02$. The most important difference when compared to models with $f=0.01$ (central-left panel) is smaller extension of the blue loops and hence there are no unstable models present during this evolutionary phase.

In the bottom-right panel of Fig.\[fig1\] we present models calculated with $Z=0.015$, OPAL opacity tables and element diffusion. MESA calculates element diffusion by solving Burgler’s equations using the method and diffusion coefficients of Thoul et al. (1994). The effect of diffusion on the shape of evolution tracks and instability areas is negligible, both for models before and after core helium ignition. The small changes of abundances of chemical elements in the central regions of the star do not modify significantly a behaviour of pulsation modes. The minor differences of frequencies might be important during 