  We present an early broad-brush analysis of Herschel/PACS observations of
star-forming galaxies in 8 galaxy clusters drawn from our survey of 30 clusters
at z~0.2. We define a complete sample of 192 spectroscopically confirmed
cluster members down to L_TIR>3x10^10L_sun and L_K>0.25L_sun. The average
K-band and bolometric infrared luminosities of these galaxies both fade by a
factor of ~2 from clustercentric radii of 2r_200 to ~0.5r_200, indicating that
as galaxies enter the clusters ongoing star-formation stops first in the most
massive galaxies, and that the specific star-formation rate (SSFR) is
conserved. On smaller scales the average SSFR jumps by 25%, suggesting that in
cluster cores processes including ram pressure stripping may trigger a final
episode of star-formation that presumably exhausts the remaining gas. This
picture is consistent with our comparison of the Herschel-detected cluster
members with the cluster mass distributions, as measured in our previous
weak-lensing study of these clusters. For example, the spatial distribution of
the Herschel sources is positively correlated with the structures in the
weak-lensing mass maps at 5sigma significance, with the strongest signal seen
at intermediate group-like densities. The strong dependence of the total
cluster IR luminosity on cluster mass L_TIR propto M_virial^2 is also
consistent with accretion of galaxies and groups of galaxies (i.e. the
substructure mass function) driving the cluster IR luminosity. The most
surprising result is that roughly half of the Herschel-detected cluster members
have redder S_100/S_24 flux ratios than expected, based on the Rieke et al.
models. On average cluster members are redder than non-members, and the
fraction of red galaxies increases towards the cluster centers, both of which
indicate that these colors are not attributable to systematic photometric
errors. [Abridged]
