Direct-development
Guides
Armadillidium vulgare
common pill-bug, common pill woodlouse, roly-poly, potato bug, doodle bug, carpenter
Armadillidium vulgare is a terrestrial isopod native to Mediterranean Europe that has become one of the most widespread woodlouse species globally through human-mediated dispersal. It is the most extensively studied terrestrial isopod and serves as a model organism for research on mitochondrial genome evolution, desiccation resistance, and conglobation behavior. The species exhibits remarkable morphological plasticity, including numerous color morphs maintained through selective breeding in the pet trade.
Caprellidae
Skeleton Shrimp, Ghost Shrimp
Caprellidae is a family of marine amphipods known as skeleton shrimps, characterized by their slender, threadlike bodies that provide camouflage among seaweed, hydroids, and bryozoans. They exhibit extreme sexual dimorphism, with males typically much larger than females. The family contains 88 genera across three subfamilies and is distributed worldwide in marine environments from intertidal zones to deep sea depths. Some species have been documented as invasive, spreading through biofouling on aquaculture equipment.
Crangonyx
cave amphipods, spring amphipods
Crangonyx is a genus of freshwater amphipod crustaceans in the family Crangonyctidae. Species inhabit diverse aquatic environments including surface waters (marshes, swamps, lakes, rivers) and subterranean habitats (caves, springs, groundwater systems). The genus includes both native and highly invasive species, with some taxa exhibiting troglobitic adaptations such as reduced eyes and elongated appendages. Several species have been introduced outside their native ranges, notably Crangonyx pseudogracilis and C. floridanus in Europe and Asia, where they interact competitively and predatorily with native amphipods.
Holoverticata
Woodlice and Pillbugs
Holoverticata is an infraorder of isopod crustaceans encompassing the familiar terrestrial woodlice and pillbugs. Members of this group are distinguished by their dorsoventrally flattened bodies, seven pairs of walking legs, and ability to occupy moist terrestrial habitats. The group includes species capable of conglobation (rolling into a ball) as well as those that remain flattened. This infraorder represents the most successful lineage of crustaceans to colonize land.
Idoteidae
Common Valvetails
Idoteidae is a family of aquatic isopod crustaceans in the suborder Valvifera, distributed globally in marine and freshwater habitats. The family includes approximately 20 genera and numerous species, with highest diversity in temperate coastal waters. Members range from free-living forms in macroalgae and seagrass beds to commensal species associated with other marine organisms. The family has been extensively studied in Australia, New Zealand, the northeastern Pacific, and the North Atlantic.
Jaera
Jaera is a genus of small marine isopods in the family Janiridae, comprising more than 20 described species. The genus is notable for the Jaera albifrons species complex, a group of closely related, sympatric species that exhibit fine-scale habitat partitioning along intertidal shores. These isopods are euryhaline, capable of osmoregulation across wide salinity ranges from freshwater-influenced areas to fully marine conditions. The group has been extensively studied for its ecological differentiation, reproductive isolation, and as a model for understanding speciation processes in marine environments.
Ligiidae
Rock Lice, Sea Slaters
Ligiidae is a family of large, dorsoventrally flattened terrestrial isopods commonly known as rock lice or sea slaters. These crustaceans inhabit rocky intertidal zones and adjacent coastal habitats, where they hide during daylight hours and emerge at night to scavenge. They represent the sole family within the infraorder Diplocheta and are distinguished from other woodlice by their elongated body form, large size (up to 30 mm), long antennae, and preference for marine-influenced environments. The family exhibits poor desiccation resistance and limited dispersal ability, leading to pronounced population isolation and cryptic genetic diversity across their range.
Notostraca
tadpole shrimp, shield shrimp
Notostraca is an order of small crustaceans commonly known as tadpole shrimp or shield shrimp. The group contains a single extant family, Triopsidae, with two genera: Triops and Lepidurus. These animals are considered living fossils, with morphologically similar forms dating back to the Late Devonian approximately 360 million years ago. They inhabit temporary freshwater pools, shallow lakes, and similar aquatic environments worldwide except Antarctica.
Oniscidae
sow bugs, woodlice
Oniscidae is a family of terrestrial isopods (woodlice) within the suborder Oniscidea. The family includes the common woodlouse Oniscus asellus and at least six confirmed genera: Oniscus, Oroniscus, Phalloniscus, Rabdoniscus, Rodoniscus, and Sardoniscus. Members are detritivores that contribute to decomposition and nutrient cycling in terrestrial ecosystems. Some species exhibit behavioral sensitivity to environmental contaminants, suggesting potential use as bioindicators.
Oniscidea
Woodlice, Pillbugs, Rock Slaters
Oniscidea is the suborder of terrestrial isopod crustaceans commonly known as woodlice, pillbugs, and rock slaters. This diverse group comprises over 5,000 described species that have successfully colonized land from ancestral marine isopod stock. They are characterized by a dorsoventrally flattened, segmented exoskeleton with seven pairs of walking legs, and occupy a wide range of habitats from forests and grasslands to caves and urban environments. Most species are nocturnal detritivores that play important roles in decomposition and nutrient cycling.
Peracarida
Amphipods, Isopods, and Allies
Peracarida is a superorder of malacostracan crustaceans comprising approximately 12,000 species across 13 orders. The group is defined by the presence of a marsupium (brood pouch) formed by oostegites—flattened plates on the basalmost leg segments of females. Members occupy marine, freshwater, and terrestrial habitats, ranging from minute interstitial forms to the giant isopod Bathynomus giganteus (76 cm) and giant amphipod Alicella gigantea (34 cm). The earliest known peracaridian, Oxyuropoda ligioides, dates to the Late Devonian (~360 mya).
Tanaidacea
Tanaids
Tanaidacea is a minor order of small, shrimp-like crustaceans within the class Malacostraca. The group contains approximately 940 described species, ranging from 0.5 to 120 mm in adult size. Tanaids are primarily marine benthic organisms that inhabit bottom sediments, with a few species occurring in freshwater. They exhibit direct development without a planktonic larval stage, with young emerging from the maternal marsupium as post-larvae called mancas. The fossil record extends to the Carboniferous period.