Location of the several classes of pulsating WD stars in the log T_eff − log g plane, marked with dots of different colours. In parenthesis we include the number of known members of each class. Two post-VLTP (Very Late Thermal Pulse) evolutionary tracks are plotted for reference. We also show the theoretical blue edge of the instability strip for the GW Vir stars, V777 Her stars, the DQV stars (Córsico et al. 2006, 2009a,b, respectively), the ZZ Ceti stars (Fontaine & Brassard 2008), and the pulsating low-mass WDs. For this last class, we show the blue edge according to Hermes et al. (2013a; dotted red line), Córsico et al. (2012; solid red line), and Steinfadt et al. (2010; dashed red line). For reference, we also include two evolutionary tracks of low-mass He-core white dwarfs from Althaus et al. (2013). Small black dots correspond to low-mass WDs that are non-variable or have not been observed yet to assess variability.