Illustration of the ms-WR, w-WR, wb-WR, and w-WR formation channels of WR stars. Shown are evolution tracks calculated at a metallicity Z = 0.008 (≈Z_LMC) with the BPASS code for single stars with initial masses M_i = 100, 50, and 25 M_⊙ (upper, middle, and dashed lower tracks, respectively). Also plotted are BPASS binary evolution tracks with M_i = 50 M_⊙, P_i = 25 d, q_i = 0.7 (upper), and M_i = 25 M_⊙, P_i = 25 d, q_i = 0.7 (lower). The colors correspond to surface hydrogen mass fractions (blue: 0.4 <  X_H <  0.74, red: 0.2 <  X_H <  0.4, orange: 0.05 <  X_H <  0.2, green: X_H <  0.05). Empirically, stars found in the dashed region are not expected to show a WR spectrum (see Sect. 6.1.3).