Body elongated, outline interrupted between pereon and pleon, epimeres of pleon reduced. The flagellum of antennae is composed of three segments. Each eye is made up of a group of ocelli (from 7 to 20 in different species). Pleopodal lungs absent. Colours when live mottled brown, body size in different species 5-8mm. Runs fast when disturbed, and does not roll into a ball.
A common group in native New Zealand environments. Currently, nine species are described from New Zealand (Vandel, 1977). Genus-level classification is unresolved, and species-level identification is difficult and requires microscopic examination.