ABSTRACT
Isopod crustaceans exemplify the evolutionary transition of animals from aquatic to terrestrial habits, and genus Ligia exemplifies the prototypal land isopod. Morphological characteristics of ligiid pleopods and oostegites, physiological characteristics of oxygen consumption^water uptake, and nutrition, and behavioural characteristics of swimming and orienting ability, all number among ligiid features which are transitional between ancestral marine and fully terrestrial forms. While such features are transitional in the sense of sea-to-land evolution, they nonetheless adapt ligiids to be successful in their semiterrestrial habit.
