  Early-type dwarf galaxies dominate cluster populations, but their formation
and evolutionary histories are poorly understood. The ALFALFA (Arecibo Legacy
Fast ALFA) survey has completed observations of the Virgo Cluster in the
declination range of 6 - 16 degrees. Less than 2% of the early-type dwarf
population is detected, a significantly lower fraction than reported in
previous papers based on more limited samples. In contrast ~30 of the
irregular/BCD dwarf population is detected. The detected early-type galaxies
tend to be located in the outer regions of the cluster, with a concentration in
the direction of the M Cloud. Many show evidence for ongoing/recent star
formation. Galaxies such as these may be undergoing morphological transition
due to cluster environmental effects.
