  The Blue Large-Amplitude Pulsators (BLAPs) constitute a new class of
pulsating stars. They are hot stars with effective temperatures of $T_{\rm
eff}\sim 30\,000$ K and surface gravities of $\log g \sim 4.9$, that pulsate
with periods in the range $\sim 20-40$ min. In Romero et al. (2018), we
proposed that BLAPs are hot low-mass He-core pre-white dwarf (WD) stars that
pulsate either in high-order non-radial $g$(gravity) modes or low-order radial
modes, including the fundamental radial mode. The theoretical modes with
periods in the observed range are unstable due to the $\kappa$ mechanism
associated with the $Z$ bump in the opacity at $\log T \sim 5.25$. In this
work, we extend the study of Romero et al. (2018) by assessing the rate of
period changes of nonradial $g$ modes and radial modes and comparing them with
the values measured for BLAPs, in an attempt to validate the proposed
evolutionary scenario, and to discern whether the observed modes are high-order
$g$ modes or radial modes.
