  We have used NASA's TESS mission to study catalogued delta Scuti stars. We
examined TESS light curves for 434 stars, including many for which few previous
observations exist. We found that 62 are not delta Scuti pulsators, with most
instead showing variability from binarity. For the 372 delta Scuti stars, we
provide a catalogue of the period and amplitude of the dominant pulsation mode.
Using Gaia DR3 parallaxes, we place the stars in the period-luminosity diagram
and confirm previous findings that most stars lie on a ridge that corresponds
to pulsation in the fundamental radial mode, and that many others fall on a
second ridge that is a factor two shorter in period. This second ridge is seen
more clearly than before, thanks to the revised periods and distances. We
demonstrate the value of the period-luminosity diagram in distinguishing delta
Scuti stars from short-period RR Lyrae stars, and we find several new examples
of high-frequency delta Scuti stars with regular sequences of overtone modes,
including XX Pyx and 29 Cyg. Finally, we revisit the sample of delta Scuti
stars observed by Kepler and show that they follow a tight period-density
relation, with a pulsation constant for the fundamental mode of Q = 0.0315 d.
