Top and bottom left-hand graphs: Δe dynamicalmap for system HD 74156 as obtained from the numerical integration of a grid of 900 × 900 initial conditions in the (a₂, e₂) plane. Upperplot: corresponds to a semimajor axis a₂ ∈ [0.80, 0.95] au, and the bottom panel to a semimajor axis a₂ ∈ [0.95, 1.10] au. The integration time was set to 10³ yr, and escapes during this time span are highlighted in light yellow. The location of the middle planet is shown with a filled white circle. The libration widths of the most relevant MMRs determined analytically are highlighted in blue (resonances with the outer planet) and red (resonance with the inner planet). Top and bottomright-hand graphs: Megno map for the same plane. The set of initial conditions was reduced to a 300 × 300 grid, but the integration time was extended to 10⁴ yr.