Most species are less than 10 mm long but some can be twice this length. They can swim but do so upside-down. They are brooders as are all isopods and females of some species develop deep cavities underneath to house the eggs and young. The family is the most commonly seen and most diverse of all isopods in southern Australia. Some of the many species are highly ornamented.
Males are often more elaborately sculptured with knobs and spikes than their mates.