This family of lice are parasites of seals and the river otter, and are the only insects that infest aquatic hosts.

Because some marine mammals, such as fur seals, have a layer of air trapped under their waterproof coats that insulates them against cold water, their lice actually live in a mostly dry, warm habitat.

Other mammals have blubber for insulation, so their skin is in contact with the water; their lice parasites live in a cold aquatic environment.

Species also have various egg-laying habits, with some laying them singly or in clusters, and some cementing them to the hairs of the host animal.

Proechinophthirus fluctus lives under the fur, while Antarctophthirus callorhini prefers parts with naked skin, such as the nostrils and eyelids of the host.