Left panel: relation between ν_max and the mean frequency of the envelope for δ Scuti stars (green triangles). The black line points to the 1:1 relation. Blue dashed lines are the limits for a significant departure from the solar case (3σ, see text). Right panel: distribution of stars according to their asymmetry (black histogram). The blue (red) histogram denotes the proportion of stars whose ν_max deviation from the mean frequency of the envelope towards lower (higher) frequencies is significantly higher than the solar case (see text).