Ages of the youngest stellar populations at the SN locations, estimated through the measured Hα EW and Starburst99 (Leitherer et al. 1999) (range denoted by solid line; see text). These set a lower limit (dashed line) to the age of the SN birthplace. The SN environments were ordered by ascending metallicity, and some key values are indicated on the righthand axis, but this is only for illustration purposes as this axis does not have any meaningful scale. The color coding is the same as in Fig. 2: blue for SNe Ib, red for SNe Ic and black for intermediate SNe Ib/c. The interloper type Ia SN 2007qw is in magenta. The horizontal dashed line separates the galaxies into two metallicity groups depending on whether a comparison with Z = 0.008 or Z = 0.02 models is more appropriate. The vertical dashed lines denote the predictions of the Geneva evolutionary codes for the lifetimes of single massive stars of 25 M_⊙ at Z = 0.02 and 30 M_⊙ at Z = 0.008 (Meynet & Maeder 2003, 2005). The allowed ages for single progenitors of SNe Ib/c are illustrated by the gray-shaded area.