Freshwater
Guides
Argia translata
Dusky Dancer
Argia translata, commonly known as the Dusky Dancer, is a damselfly species in the family Coenagrionidae. It is native to eastern and southern North America and has also been documented in parts of Central and South America. The species is relatively well-observed, with over 11,000 records on iNaturalist, suggesting it is not uncommon in suitable habitats. As with other members of the genus Argia, it is associated with freshwater environments where it completes its aquatic larval development before emerging as a flying adult.
Argyractini
Argyractini is a tribe of aquatic moths within the subfamily Acentropinae (Crambidae). The tribe includes several genera of small to medium-sized moths whose larvae are adapted to life in freshwater habitats. Adults are generally nocturnal and are attracted to light. The group is primarily distributed in the New World, with most species occurring in the Neotropical region.
Argyractis drumalis
Argyractis drumalis is a small aquatic moth in the family Crambidae, subfamily Acentropinae. It is endemic to Florida and associated with freshwater aquatic habitats. The species is named for Fort Drum, its type locality. Adults are active year-round with peak presence from February through November.
Arrenuridae
Arrenuridae is a family of water mites (Hydrachnidia) in the order Trombidiformes, containing at least three genera and approximately 110 described species. Members are primarily freshwater predators as adults and deutonymphs, with larvae that parasitize aquatic insects. The family exhibits complex mating behaviors mediated by chemical communication, including female-emitted sex pheromones that trigger male responses.
Arrenurus
water mites
Arrenurus is the largest genus of water mites, comprising approximately 950 species with cosmopolitan distribution in lentic freshwater habitats. Adults are heavily sclerotized, predatory, and exhibit marked sexual dimorphism—males possess diagnostic caudal modifications used in mating, while female taxonomy remains problematic. The life cycle includes seven stages: egg, inactive prelarva, parasitic larva, protonymph, deutonymph, tritonymph, and adult. Larvae are ectoparasites of aquatic insects, particularly Odonata (dragonflies and damselflies), but also Diptera and Coleoptera, utilizing hosts for both nutrition and phoretic dispersal.
Arrenurus problecornis
Arrenurus problecornis is a species of water mite (family Arrenuridae) described by Cook in 1976. Like other members of the genus Arrenurus, it is part of the subgenus Arrenurus, which is characterized by parasitic larvae that attach to odonate hosts (dragonflies and damselflies). The species belongs to the diverse radiation of water mites (Hydrachnidia), a group comprising over 6,000 species of predatory freshwater arachnids with complex life histories involving parasitic larval stages and free-living predatory adults.
Arthropleidae
flatheaded mayflies
Arthropleidae is a family of mayflies in the order Ephemeroptera, characterized by flattened heads. The family contains at least two genera: the extant Arthroplea and the extinct Electrogenia. Members are aquatic insects with life cycles involving aquatic nymphal stages and short-lived winged adults.
Aselloidea
Waterslaters and allies
Aselloidea is a superfamily of freshwater and subterranean isopods within the suborder Asellota. Members are primarily aquatic, with many lineages adapted to life in groundwater, caves, and karst systems. The superfamily includes families such as Asellidae (common freshwater isopods), Stenasellidae, and Atlantasellidae. Some representatives exhibit remarkable morphological specializations for subterranean existence, including reduced eyes and elongated appendages.
Asellota
Asellotes
Asellota is a suborder of isopod crustaceans comprising approximately one-quarter of all marine isopods. The group exhibits remarkable ecological diversity, occurring in marine, freshwater, and subterranean habitats from shallow coastal waters to abyssal depths, including hydrothermal vents. Members possess distinctive morphological specializations including a complex copulatory apparatus that distinguishes them from other isopods. The suborder has undergone multiple independent colonizations of deep-sea environments, with some lineages showing extensive radiation in these habitats.
Astacidae
Astacid Crayfishes, Freshwater Crayfish
Astacidae is a family of freshwater crayfish comprising four extant genera: Astacus, Austropotamobius, Pontastacus, and Pacifastacus. Members are native to Europe, western Asia, and western North America. The family is distinguished by a gonopore positioned on the coxa of the third pair of walking legs in males (fifth pair in females), a trait shared with all Astacoidea. Several species, particularly Pacifastacus leniusculus (signal crayfish), have become invasive outside their native ranges, carrying crayfish plague (Aphanomyces astaci) that threatens native European populations.
Astacoidea
Northern Hemisphere Crayfishes
Astacoidea is a superfamily of freshwater crayfish restricted to the Northern Hemisphere. It comprises three families: Astacidae (Europe and western North America), Cambaridae (eastern North America), and Cambaroididae (eastern Asia). Members are distinguished from the Southern Hemisphere superfamily Parastacoidea by geographic distribution. Crayfish in this group possess ten walking legs, feather-like gills for respiration, and a segmented body with a hard exoskeleton. Many species construct burrows for shelter, with complexity varying from simple tunnels to elaborate multi-chambered systems.
Asynarchus
Asynarchus is a genus of caddisflies in the family Limnephilidae, first described by McLachlan in 1880. Species are found in small, cold, oligotrophic lakes and ponds across Eurasia and Northern America. The genus includes at least two species: A. contumax and A. lapponicus. Larvae and pupae of both species have been described from central Norway.
Atrichomelina
snail-killing flies
Atrichomelina is a genus of marsh flies (family Sciomyzidae) whose larvae are predators of freshwater snails. The genus was established by Cresson in 1920 and contains at least one described species, Atrichomelina pubera. Like other sciomyzids, members of this genus have aquatic or semi-aquatic immature stages that develop in association with mollusk hosts.
Aturus
Aturus is a genus of water mites in the family Aturidae, first described by Kramer in 1875. These mites are part of the diverse Trombidiformes order, which includes many aquatic and terrestrial predatory mites. The genus has a notably broad geographic distribution spanning multiple continents.
Baetidae
small mayflies, small minnow mayflies
Baetidae is the most species-diverse family of mayflies, comprising approximately 1,000 described species in 110-114 genera worldwide and representing about one-third of all mayfly diversity. Adults are among the smallest mayflies, rarely exceeding 10 mm in length excluding tails, with some species much smaller. The family has a cosmopolitan distribution except for New Zealand and occupies a relatively basal position in Ephemeroptera phylogeny.
Baetis notos
Baetis notos is a species of small minnow mayfly in the family Baetidae. It is found in Central America and North America, with its North American range extending across southern Mexico, the southern United States, and the northwestern United States. The species was described by Allen and Murvosh in 1987.
Banksiola
Traveller Sedges, Giant Casemakers
Banksiola is a genus of caddisflies in the family Phryganeidae, commonly known as giant casemakers or traveller sedges. The genus comprises approximately five described species distributed in North America. Larvae construct portable cases from plant material and are associated with freshwater habitats.
Bdelloidea
Bdelloid rotifers, bdelloids
Bdelloidea is a class of microscopic rotifers found in freshwater habitats worldwide, comprising over 450 described species. These organisms are distinguished by obligate parthenogenetic reproduction—no males have ever been observed—and their remarkable ability to survive extreme desiccation through anhydrobiosis. They range from 150–700 μm in length and can remain dormant for years, with documented cases of revival after 24,000 years frozen in Siberian permafrost. Bdelloids have been called 'ancient asexuals' due to their estimated 25+ million year history of asexual reproduction supported by fossil evidence.
Bellura
Bellura is a genus of moths in the family Noctuidae, established by Walker in 1865. The genus contains approximately eight described species distributed in North America. Caterpillars of at least some species are aquatic or semi-aquatic, feeding on aquatic plants such as water lilies. The genus is notable among Noctuidae for this aquatic larval ecology, which is relatively uncommon in the family.
Bellura gortynoides
White-tailed Diver Moth, white-tailed diver
Bellura gortynoides, commonly known as the white-tailed diver moth, is a North American noctuid moth whose aquatic caterpillars live submerged in freshwater habitats. The larvae feed on aquatic plants, including water lilies, and breathe by periodically surfacing to capture air through specialized spiracles. Adults are strictly nocturnal. The species belongs to the poorly studied group of aquatic moths, which have received limited scientific attention despite their unusual ecology.
Bellura vulnifica
Black-tailed Diver Moth, Black-tailed Diver
Bellura vulnifica, commonly known as the black-tailed diver moth, is a North American species in the family Noctuidae. The species is part of the aquatic moth genus Bellura, whose larvae are known to inhabit freshwater environments and feed on aquatic vegetation. Adults are nocturnal. The species is assigned Hodges number 9523.1.
Belostoma
giant water bugs, electric-light bugs, toe-biters
Belostoma is a genus of giant water bugs in the family Belostomatidae, comprising approximately 70 species organized into 16 subgroups. These aquatic predators are native to freshwater habitats throughout the Americas, with highest diversity in tropical South America. The genus is distinguished by male paternal care, where males carry eggs cemented to their backs until hatching. Species range in body length from 15 to 41.5 mm.
Belostoma confusum
Belostoma confusum is a species of giant water bug in the family Belostomatidae, described by Lauck in 1959. As a member of this family, it is an aquatic predator found in freshwater habitats. The species occurs in North America and Middle America based on distribution records. Like other Belostoma species, it possesses raptorial forelegs adapted for capturing prey and likely exhibits the reversed sexual size dimorphism characteristic of the genus, where females are larger than males and males carry eggs on their backs.
Belostoma fusciventre
Belostoma fusciventre is a species of giant water bug in the family Belostomatidae, first described by Dufour in 1863. Like other members of the genus Belostoma, it is an aquatic predator inhabiting freshwater environments. The species is known from Middle America and North America, though specific details about its biology and ecology remain limited in available literature.
Belostoma minor
giant water bug
Belostoma minor is a species of giant water bug in the family Belostomatidae. It occurs in the northern Caribbean bioregion, with documented records from Cuba, the Dominican Republic, Jamaica, Puerto Rico, the U.S. Virgin Islands, and southern Florida. Like other members of its genus, it is an aquatic predator. The species was described by Palisot de Beauvois in 1820.
Belostoma testaceum
giant water bug
Belostoma testaceum is a species of giant water bug in the family Belostomatidae. It is found in the eastern United States, ranging from New York south to southern Florida and west to Texas and Michigan. Like other members of its family, it is an aquatic predator inhabiting freshwater environments.
Belostomatidae
giant water bugs, toe-biters, Indian toe-biters, electric-light bugs, alligator ticks, alligator fleas
Belostomatidae is a family of large freshwater hemipteran insects comprising approximately 170 species worldwide. Members are the largest insects in the order Hemiptera, with some species exceeding 12 cm in length. They are aggressive predators found in ponds, marshes, and slow-flowing streams, feeding on aquatic invertebrates, fish, amphibians, and even small vertebrates. The family exhibits remarkable paternal care, with males of many species carrying eggs on their backs until hatching. Several species are consumed as food in Southeast Asia.
Benthalia
Benthalia is a genus of non-biting midges in the family Chironomidae, established by Lipina in 1939. The genus is currently treated as a synonym of Einfeldia in the Catalogue of Life, reflecting ongoing taxonomic revision in the Chironomini tribe. Species historically placed in Benthalia are primarily benthic, inhabiting the bottom sediments of aquatic environments.
Berosus peregrinus
Berosus peregrinus is a water scavenger beetle (Hydrophilidae) native to North America and the Caribbean. It inhabits freshwater environments including marshes, ponds, and sluggish streams. Like other members of its genus, it is adapted to aquatic life and contributes to decomposition of organic material in aquatic ecosystems.
Bidessini
Bidessini is a tribe of predaceous diving beetles within the family Dytiscidae, comprising at least 40 genera and over 630 described species. Members are small to minute aquatic beetles found across diverse freshwater habitats worldwide, with notable radiations in Australia, South America, and Madagascar. The tribe includes both surface-dwelling (epigean) and subterranean (stygobitic) species, with several genera exhibiting convergent adaptations to groundwater environments.
Bidessonotus
Bidessonotus is a genus of predaceous diving beetles in the family Dytiscidae, first described by Régimbart in 1895. The genus comprises approximately 30 described species distributed primarily in the Americas, with records from North America through Central America to northern South America. These small diving beetles inhabit freshwater environments and are members of the tribe Bidessini within the subfamily Hydroporinae. The genus was revised taxonomically by Young in 1990, who described numerous new species.
Bolotoperla rossi
Smoky Willowfly
Bolotoperla rossi is a species of stonefly in the family Taeniopterygidae, commonly known as the Smoky Willowfly. Originally described as Brachyptera rossi by Frison in 1942, it was later transferred to the genus Bolotoperla. This species belongs to the winter stonefly group, which are active during cold months when most other insects are dormant.
Bosmina
water flea
Bosmina is a genus of small cladoceran crustaceans commonly known as water fleas. Members are distinguished from the related genus Bosminopsis by having antennae that are separated at their bases rather than fused. Bosmina species are filter feeders that consume algae and protozoans approximately 1–3 μm in size, using a dual feeding mechanism involving mesh-like setules on the second and third legs for filtering while the first leg grasps particles. The genus exhibits notable morphological plasticity, particularly in posterior mucrones and anterior antennules, which vary in response to predation pressure. Some Bosmina species have become invasive outside their native ranges, posing threats to aquatic ecosystems.
Bosmina freyi
Bosmina freyi is a small cladoceran crustacean in the family Bosminidae, described by De Melo and Hebert in 1994. It inhabits freshwater environments, with documented populations in tropical eutrophic reservoirs. Research has examined morphological plasticity in this species, particularly variation in body size, mucron length, and antennule morphology in response to environmental conditions.
Brachycentridae
Humpless Casemaker Caddisflies
Brachycentridae is a family of caddisflies (order Trichoptera) commonly known as humpless casemaker caddisflies. The family contains approximately 100 species across 8 genera and is distributed across North America, Europe, and Asia. Larvae construct portable cases using plant material, rock fragments, or silk, with some species exhibiting specialized filter-feeding behaviors. The family was first described by Georg Ulmer in 1903 as a subfamily of Sericostomatidae before being elevated to family rank.
Brachycentrus
Grannom Caddisflies, Humpless Casemaker Caddisflies
Brachycentrus is a genus of caddisflies in the family Brachycentridae, commonly known as grannoms or humpless casemaker caddisflies. The genus contains at least 30 described species distributed across North America and Eurasia. Larvae are aquatic filter-feeders that construct portable cases from silk and environmental materials such as sand, small stones, or plant fragments. The genus is ecologically significant as an important prey item for trout and other freshwater fish.
Brachycentrus americanus
American Grammon
Brachycentrus americanus is a species of humpless casemaker caddisfly in the family Brachycentridae. Larvae construct portable cases and are sensitive to synthetic pyrethroid insecticides, exhibiting case-abandonment behavior upon exposure. The species displays diel periodicity in activity patterns, with predominantly nocturnal filtering behavior. It is most active in July and August in western and midwestern North America.
Brachycentrus incanus
Brachycentrus incanus is a species of caddisfly in the family Brachycentridae. The species was described by Hagen in 1861 and is known from the Nearctic region. Like other members of its family, it is associated with freshwater habitats where larvae construct portable cases.
Brachycercus
squaregilled mayflies
Brachycercus is a genus of small mayflies in the family Caenidae, commonly known as squaregilled mayflies. The genus is characterized by its distinctive square-shaped gills and is distributed primarily in the Palaearctic and Nearctic realms. At least six species have been described, including B. harrisella, which is the type species described by Curtis in 1835.
Branchinecta
fairy shrimp
Branchinecta is a genus of fairy shrimp (Anostraca) comprising approximately 50 species distributed across all continents except Australia. The genus includes the largest anostracan, Branchinecta gigas, reaching up to 10 cm in length, and the highest-altitude crustacean, B. brushi, recorded at 5,930 m elevation. Species occupy diverse temporary freshwater habitats from Arctic and Antarctic regions to high-elevation Andean pools. Two species, B. gaini and B. granulosa, have been synonymized based on molecular evidence showing insufficient genetic differentiation.
Branchiopoda
Branchiopods
Branchiopoda is a class of small, primarily freshwater crustaceans unified by the presence of gills on their appendages—giving the group its name from Greek 'bránkhia' (gill) and 'poús' (foot). The class comprises fairy shrimp (Anostraca), tadpole shrimp (Notostraca), clam shrimp (Spinicaudata, Laevicaudata, Cyclestherida), and water fleas (Cladocera/Diplostraca), plus the extinct Devonian Lepidocaris. Most are filter-feeders on plankton and detritus, though notostracans are opportunistic omnivores. Many species inhabit temporary pools and produce desiccation-resistant resting eggs, allowing survival through dry periods.
Brevitentoria
caddisflies
Brevitentoria is an infraorder of Trichoptera (caddisflies) within the suborder Integripalpia, established by Weaver in 1984. It comprises families of case-making caddisflies characterized by shortened, reduced tentoria in the adult head skeleton. A comprehensive inventory in Espírito Santo State, Brazil documented 40 species from 3,420 adult specimens, including three newly described species in the genera Phylloicus, Helicopsyche (Feropsyche), and Marilia. The estimated total species richness for this infraorder in the state is approximately 72 species.
Brillia
Brillia is a genus of non-biting midges in the subfamily Orthocladiinae of the family Chironomidae. The genus exhibits remarkable cryptic diversity, with DNA barcoding studies revealing 30 Barcode Index Numbers and 158 unique haplotypes across 13 described species. East Asian and North American populations show complete genetic distinctness, suggesting long-term isolation. The larvae inhabit freshwater depositional zones and serve as sensitive bioindicators for ecosystem monitoring.
Brychius
crawling water beetles
Brychius is a genus of small aquatic beetles in the family Haliplidae, commonly known as crawling water beetles. The genus comprises five recognized species distributed across parts of Europe and North America. One species, Brychius hungerfordi, is federally endangered in the United States. Members of this genus inhabit freshwater environments and are associated with aquatic vegetation.
Bryelmis idahoensis
riffle beetle
Bryelmis idahoensis is a species of riffle beetle in the family Elmidae, described by Barr in 2011. Riffle beetles are aquatic insects that inhabit fast-flowing streams and rivers. The species is known from North America, with its specific epithet suggesting a connection to Idaho. As with other members of Elmidae, it likely has an aquatic larval stage and a partially aquatic adult stage, though specific biological details for this species remain undocumented in available sources.
Buenoa arida
Buenoa arida is a species of backswimmer in the family Notonectidae, first described by Truxal in 1953. The genus Buenoa comprises aquatic predatory insects that swim upside down. This species is part of a diverse group of true bugs adapted to freshwater environments.
Buenoa confusa
Buenoa confusa is a species of backswimmer (family Notonectidae) described by Truxal in 1953. It is distributed across the Caribbean, Central America, and North America. As a member of the genus Buenoa, it is an aquatic true bug that inhabits freshwater environments.
Buenoa platycnemis
Buenoa platycnemis is a species of backswimmer in the family Notonectidae. It is a predatory aquatic insect found in freshwater habitats across the Americas. The genus Buenoa is distinguished by males producing audible stridulatory sounds, a rare trait among aquatic Heteroptera. This species has been recorded from North, Central, and South America, including multiple states in Brazil.
Buenoa scimitra
backswimmer
Buenoa scimitra is a backswimmer (Hemiptera: Notonectidae) first described by Bare in 1925. It inhabits freshwater environments across North America, the Caribbean, and Middle America. The species is a documented predator of mosquito larvae and serves as a known host for the parasitic water mite Hydrachna virella, which attaches to multiple instars and adults.
Bythotrephes longimanus
Spiny Water Flea, Spiny Waterflea
Bythotrephes longimanus is a predatory planktonic cladoceran crustacean native to northern Europe and Asia that has become a significant invasive species in North America since its introduction to the Great Lakes in the 1980s. Adults reach up to 15 mm in length, with females growing substantially larger than males. The species exhibits cyclic parthenogenesis and produces distinctive morphological forms depending on reproductive mode and season. Its invasion has caused substantial ecological disruption through direct predation on native zooplankton and non-lethal effects that alter prey behavior and population dynamics.