Fig. 5.

Eigenvalues of the internal equilibrium for a=0.8, b=10, c=1, d=9, $r_1=1$, and $r_2\in (1,5)$. The real parts of the eigenvalues are depicted by the solid curves, their imaginary parts by the dashed curves. Eigenvalues turn complex at $r_2\approx 2.01$, the Hopf bifurcation occurs at $r_2\approx 4.46$.