Equivalent width of the Li i 6708 Å feature (EW(Li)) versus V − I. Objects selected as candidate members are marked with blue diamonds; red circles mark objects that are potential members based on their photospheric Li content, but fall outside the sequence of members in the colour–magnitude diagram (see Fig. 4). Triangles mark upper limits. The solid red lines show theoretical isochrones at 10 Myr and 20 Myr from the models of Baraffe et al. (1998, see text), reddened with E(V − I) = 0.055. The dashed line marks the upper envelope of EW(Li) for IC 2391 and IC 2602 at ages ≃50 Myr.