Evolutionary tracks of stars with initial masses 5.5 and 6.2 M_⊙ (α_ov = 0.2) near the first crossing of the instability strip. Dashed lines show the blue and red edges of the instability strip. The dotted line shows the mode switch boundary. The star symbols show the location of models with the pulsation period Π_⋆ = 3.969 d.