  The mid-infrared (mid-IR) wavelength regime offers several advantages for
following the late-time evolution of supernovae (SNe). First, the peaks of the
SN spectral energy distributions shift toward longer wavelengths following the
photospheric phase. Second, mid-IR observations suffer less from effects of
interstellar extinction. Third, and perhaps most important, the mid-IR traces
dust formation and circumstellar interaction at late-times (>100 days) after
the radioactive ejecta component fades. The Spitzer Space Telescope has
provided substantial mid-IR observations of SNe since its launch in 2003. More
than 200 SNe have been targeted, but there are even more SNe that have been
observed serendipitously. Here we present the results of a comprehensive study
based on archival Spitzer/IRAC images of more than 1100 SN positions; from this
sample, 119 SNe of various subclasses have been detected, including 45 SNe with
previously unpublished mid-IR photometry. The photometry reveal significant
amounts of warm dust in some cases. We perform an in-depth analysis to
constrain the origin and heating mechanism of the dust, and present the
resulting statistics.
