Isopod
Guides
Pentidotea montereyensis
Pentidotea montereyensis is a marine isopod in the family Idoteidae, first described by Maloney in 1933. The species is found in the temperate northern Pacific Ocean and is associated with kelp and algal habitats. Like other idoteid isopods, it is dorsoventrally flattened and adapted for clinging to macroalgae. The species has been documented through 254 iNaturalist observations, indicating moderate contemporary recording effort.
Philoscia muscorum
Common Striped Woodlouse, Fast Woodlouse
Philoscia muscorum is a common European woodlouse notable for its rapid movement and distinctive appearance. It exhibits a unique life history strategy called year class splitting, where individuals from the same reproductive cohort diverge into two developmental pathways: faster-growing individuals mature and reproduce in their first year, while slower-growing individuals delay maturation until their second year. This species has successfully established introduced populations in eastern North America, including New England, the mid-Atlantic states, and the Pacific Northwest.
Porcellio scaber
Common Rough Woodlouse, Rough Woodlouse
Porcellio scaber is a European woodlouse species with a cosmopolitan distribution, now found across North America, South Africa, Australia, and sub-Antarctic islands through human-mediated dispersal. It is one of the most abundant and widespread terrestrial isopods in many regions, including the United Kingdom where it is considered one of the 'big five' woodlouse species. The species is notable for its rough, tuberculate exoskeleton and inability to conglobate (roll into a ball), instead relying on tonic immobility and chemical defenses when threatened. Research has documented individual personality traits in this species, expressed through consistent differences in defensive behavior duration.
Porcellio spinicornis
Brickwork Woodlouse
Porcellio spinicornis is a medium-sized terrestrial isopod in the family Porcellionidae, native to Europe and introduced to North America. It is distinguished by prominent spiny frontal lateral lobes, the feature referenced in its species name. The species is nocturnal and detritivorous, feeding on dead plant material. It exhibits direct development with eggs and juveniles carried in a fluid-filled marsupium until the first juvenile stage.
Porcellionides floria
Flowery Blue Isopod
Porcellionides floria is a species of terrestrial isopod (woodlouse) in the family Porcellionidae, first described by Garthwaite and Sassaman in 1985. The species has been recorded in North America and Mexico, with 89 observations documented on iNaturalist as of the source date. Like other members of its family, it is a detritivorous crustacean adapted to life on land.
Proporcellio vulcanius
Proporcellio vulcanius is a terrestrial isopod in the family Porcellionidae, described by Verhoeff in 1908. The species belongs to a genus characterized by reduced pleopodal lungs and adaptation to drier microhabitats compared to many woodlice. Records indicate presence across parts of Europe and northern Asia. The specific epithet 'vulcanius' suggests possible association with volcanic or warm habitats, though this has not been formally verified.
Rhinophoridae
Woodlouse Flies
Rhinophoridae is a small family of calyptrate flies (Diptera) comprising 33 genera and approximately 177 species. The family is distinguished by a highly specialized life history: larvae are obligate parasitoids of terrestrial isopods (woodlice), a feeding strategy unique among all insects. Adults lack morphological autapomorphies and are difficult to identify without examination of male terminalia or first-instar larvae. The group was historically considered primarily Palaearctic in distribution, but recent sampling has revealed substantial diversity in tropical and southern hemisphere regions.
Rhyscotus
armadillo woodlice
Rhyscotus is a genus of armadillo woodlice in the family Rhyscotidae, first described by Gustav Budde-Lund in 1885. The genus contains twelve recognized species distributed across multiple continents. Members of this genus are terrestrial isopods adapted to life on land.
Seroloidea
Seroloidea is a superfamily of marine isopod crustaceans within the suborder Sphaeromatidea. It comprises six families, four of which are extant and two extinct. The superfamily was established by Dana in 1852. Seroloidea is distinguished from other sphaeromatidean superfamilies by unique morphological characteristics of its constituent families, particularly the Serolidae.
Sphaeroma
pillbug, roly poly, marine pillbug
Sphaeroma is a genus of aquatic isopod crustaceans in the family Sphaeromatidae. These small crustaceans are commonly known as marine pillbugs or roly polies, though they are distinct from terrestrial isopods. The genus contains multiple species distributed across marine and estuarine environments globally. Some species, such as S. terebrans, are specialized wood-borers in mangrove habitats, while others inhabit rocky intertidal zones or construct burrows in soft sediments. The genus has been subject to recent taxonomic revision, with new species described from the northeastern Pacific and elsewhere.
Sphaeromatidae
seapills, Typical Seapills
Sphaeromatidae is a family of marine isopods commonly known as seapills, containing approximately 100 genera and 619 marine species with about 65 additional species in freshwater. Members are frequently encountered on rocky shores and in shelf waters of temperate zones. Many species exhibit dorsoventrally compressed body shapes, often with vaulted dorsums, though some are strongly flattened and scale-like. The family includes both free-living and symbiotic forms, with some genera associating with sponges or other marine organisms.
Sphaeromatidea
Seapills and allies
Sphaeromatidea is a suborder of isopod crustaceans established by Wägele in 1989, containing approximately 8587 recorded observations. The suborder comprises seven extant families across two superfamilies: Seroloidea (including Serolidae, Basserolidae, Bathynataliidae, and Plakarthriidae) and Sphaeromatoidea (including Sphaeromatidae, Ancinidae, and Tecticipitidae), plus three extinct families. Members exhibit substantial morphological diversity, with some species having colonized freshwater habitats from marine ancestors.
Sphaeromatoidea
Seapills
Sphaeromatoidea is a superfamily of isopod crustaceans commonly known as seapills. Members of this group are characterized by their ability to conglobate—roll into a ball when disturbed. The superfamily includes approximately 1,000 described species distributed across multiple families, primarily in marine and estuarine habitats. These isopods are distinguished from related groups by specific morphological features of the pleon and uropods.
Stenasellidae
Stenasellidae is a family of stygobiotic (obligate subterranean aquatic) isopods in the suborder Asellota. The family comprises approximately 10 genera including Stenasellus, Metastenasellus, and Parastenasellus, with species distributed across groundwater habitats in Africa, the Middle East, southern Europe, and Southeast Asia. These crustaceans are exclusively adapted to life in continental underground waters including caves, wells, and interstitial aquifers. Their evolutionary history has been shaped by Quaternary climatic events including aridification in tropical zones and glaciations in temperate regions.
Tecticipitidae
Hidehorns
Tecticipitidae is a family of marine isopod crustaceans established by Iverson in 1982. The family belongs to the suborder Sphaeromatidea and is commonly referred to as "Hidehorns." As a sphaeromatid family, its members are likely characterized by body forms adapted to living in interstitial spaces or under hard substrates in marine environments. The family is poorly represented in public biodiversity databases, with only nine observations recorded on iNaturalist and no distribution records available through GBIF.
Thermosphaeroma
Thermosphaeroma is a genus of isopod crustaceans in the family Sphaeromatidae, endemic to thermal springs of the southwestern United States and central Mexico. The genus contains nine described species, most of which are critically endangered or extinct in the wild due to groundwater extraction and habitat alteration. These isopods exhibit specialized adaptations to thermo-mineral spring environments, including temperature-dependent life histories and pronounced sexual dimorphism in uropod morphology. Several species have been studied for their complex social behaviors, including precopulatory mate-guarding and cannibalism.
Trichoniscidae
Trichoniscidae is a family of terrestrial isopods (woodlice) notable for containing the most abundant British woodlouse, *Trichoniscus pusillus*. The family exhibits exceptional ecological diversity, with many species occupying subterranean habitats in karst regions across Europe, while others have secondarily adapted to aquatic or amphibious lifestyles. Multiple genera contain troglobiotic (obligate cave-dwelling) species, particularly in the Dinaric Karst, which harbors significant diversity of this family. Some species demonstrate unique morphological adaptations for cave life, including elongated appendages and modified mouthparts.
Tylos
Calloused Beach Pillbugs
Tylos is a genus of terrestrial isopods (woodlice) in the family Tylidae, commonly known as calloused beach pillbugs. These crustaceans are specialized inhabitants of sandy coastal environments, living in the supralittoral zone above the driftline on ocean beaches. They exhibit remarkable adaptations for life in this harsh habitat, including powerful burrowing abilities, strong desiccation resistance, and behavioral synchronization with tidal and diel cycles. Most species are nocturnal, emerging at night to feed on beach-cast organic material such as kelp and other detritus.
Tylos niveus
Snowy Calloused Beach Pillbug
Tylos niveus is a coastal isopod in the family Tylidae, first described by Budde-Lund in 1885. A 2000 redescription provided a new diagnosis for the species and documented its expanded latitudinal distribution. The species has been recorded from sandy beach habitats in Brazil, with a new occurrence reported from Taquaras, Santa Catarina, extending its known range to 27°S.
Tylos punctatus
Spotted Calloused Beach Pillbug
Tylos punctatus is a large, strictly nocturnal sand-beach isopod inhabiting sheltered intertidal zones from southern California to Baja California. It exhibits remarkable behavioral adaptations to this harsh environment, including precise burrowing cycles synchronized with tidal patterns and seasonal dormancy. The species has an exceptionally slow life history for an isopod, with females breeding only once annually after reaching maturity at approximately three years of age.
Venezillo pisum
Venezillo pisum is a species of terrestrial isopod in the family Armadillidae, first described by Budde-Lund in 1885. The specific epithet 'pisum' (Latin for 'pea') likely refers to some aspect of its appearance or behavior, though the original description's reasoning is not preserved in available sources. As a member of the Oniscidea (woodlice and pill bugs), it is a detritivore inhabiting moist terrestrial environments. The species has been recorded in North America, though it may represent an introduced population given its original description from European material.