Osioida

Osioida is a historical taxonomic term that has been used to refer to terrestrial isopods, a group of crustaceans within the order Isopoda. In modern classifications, the terrestrial isopods are placed in the suborder Oniscidea (also known as Oniscoidea) within Isopoda. As a result, Osioida is largely considered obsolete or synonymous with Oniscidea in current taxonomy, though it may still appear in older literature or regional classifications.

Members typically have a dorsoventrally flattened body adapted to life in leaf litter, soil, and other moist microhabitats. They possess a range of adaptations for terrestrial life, including modified respiratory structures that enable gas exchange in a mainly air-breathing environment. Many woodlice are detritivores, feeding on decaying plant material and fungi, and play a role in nutrient cycling and soil formation. Most species require moist conditions and are often active at night or under cover during the day to avoid desiccation.

Reproduction occurs sexually, with females carrying eggs in a brood pouch formed by specialized appendages on the thorax. The young hatch as miniature adults and undergo direct development, gradually reaching their adult form through molts. The distribution of terrestrial isopods is cosmopolitan, with high diversity in temperate and moist tropical regions; they are less common in extremely dry or exposed habitats.

In summary, Osioida refers to a former taxonomic concept associated with terrestrial isopods. Modern usage typically designates this group as Oniscidea, the woodlice and their relatives, a well-known and ecologically important component of soil and litter communities.