Evolutionary tracks for metal-poor stars. The green track is for M_init = 40   M_⊙, Z = 10^-5 and for a rotational velocity that is v_rot = 555 km   s^-1 (Yoon et al. 2006). This model evolves homogeneously. The red track is for M_init = 85   M_⊙, Z = 10^-8 and v_rot = 800 km   s^-1 (Hirschi 2007). The blue pluses denote (L, T_eff) combinations for which mass-loss rates have been computed using abundance patterns that are typical for the surface composition of the evolutionary tracks.