Description: 20-50 mm in length. Erpobdellidae have large anterior suckers and no jaws or teeth. They are predators and typically engulf their prey. They can have 0, 3 or 4 pairs of eyes.

Habitat: 10 species occur in North America, young in cocoons are attached to hard substrates

Description: Anterior sucker fused to the head, protractible proboscis, no jaws, flattened bodies that are much wider than the head, 1-4 pairs of eyes. 7-39 mm in length.

Habitat: Occurs in streams, lakes and ponds.

Description: Less than 10 cm, however some can grow up to 40 cm long. Hirudinidae have 2 suckers at either end of body, have colorful patterns.

Habitat: Found in mostly still and slow moving warmer fresh waters, however can be found in cold, clear streams and rivers.

Description: Anterior sucker expanded, separate from the body, small mouth pore with a protrusible proboscis, more cylindrical body than the other families, 0-2 pairs of eyes. 1-2 cm in length.

Habitat: 10 species in North America