Series of reared material from Montana provide the bases for the first descriptions of the adults of Caudatella edmundsi. Male adults are differentiated from congeners based on their having abdominal sterna with dark anterior corners and penes with the gonopores subparallel and projected dorsally. The first description of Caudatella eggs shows them to have a chorion without reticulations. Larvae of C. edmundsi usually are associated with moss in moderate to slow current regions of cool, clear, shaded streams.