  In this study, pulsational and physical characteristics of two $\delta$ Scuti
stars, V775 Tau and V483 Tau, are analysed by using four-year high-precision
photometric data of STEREO satellite. Thus, it is aimed to gain new insights
into behaviours of these pulsators and evolution of $\delta$ Scuti, $\gamma$
Dor and Am type stars. The data are taken between 2007--2011 and examined with
the help of the Lomb-Scargle method. The detection precision in the four-year
combined data is around $10^{-5}$ c/d in frequency and $10^{-5}$ mag in
amplitude. It is revealed that V775 Tau exhibits weak pulsation characteristic
which is interpreted as the existence of the interaction between the helium
loss in the partial ionization zone and pulsation intensities. It is also
considered that the absence of strong pulsations is also related to the
evolution status of the star. Further, its periodogram shows low-frequency
peaks. If these oscillations are g-modes, V775 Tau can be thought to be one of
the rare stars that show all $\gamma$ Dor, $\delta$ Scuti and Am type
variations. V483 Tau is comparatively more luminous, hotter and has higher
rotational velocity. Therefore, although it shares the same region with V775
Tau in the H-R diagram, it is not considered to be an Am star. Yet, it exactly
overlaps with the $\gamma\,$ Dor stars. These clues as well as g-modes detected
in its periodogram indicate that V483\,Tau is a hybrid star. Finally, both V775
Tau and V483 Tau display period changes whose rates are between $10^{-3}$ and
$10^{-4}$ $yr^{-1}$. Considering the $\delta$ Scuti nature, it may be
speculated that these changes are non-evolutionary.
