A suborder of the Isopoda which are parasitic on various crustaceans, mainly marine forms. The females are sometimes modified so strongly as to leave almost no indication of their isopod nature. The female pierces the host's skin with the aid of styliform mandibles to suck blood. It seizes the host's skin by means of its prehensile pereiopoda. The pleopoda are respiratory in function. The dwarf male attaches to the female, from which it takes nourishment, and retains its isopod structure. The first larva, the epicardium, is free-living, while the second, the microniscium, is temporarily ectoparasitic on Copepoda. The third larval stage, the cryptoniscium, is free-swimming and seeks a final host, on which it undergoes final development to the adult. The suborder is divided into two tribes, the Cryptoniscina and Bopyrina.