The dugesiid flatworms are related to the land flatworms, and are characterised by highly flexible bodies that are usually (but not always) flattened. Like many flatworms Neppia has two obvious eyes on top of the head, but unlike other common freshwater flatworms, Neppia has distinct ear-like auricles protruding from the sides of the head.
Neppia is sometimes referred to as the “mountain flatworm” because it is common in stony bottom mountain streams.
They are predators of other freshwater invertebrates, including snails and worms.
Neppia is found in many good quality mountain streams, but it has not been assigned tolerance values. The Phylum Platyhelminthes, which includes Neppia and other more pollution-tolerant flatworms, has been assigned low tolerance values of 3 (hard bottom sites) and 0.9 (soft bottom sites).