Freshwater
Guides
Graptocorixa californica
Graptocorixa californica is a species of water boatman in the family Corixidae, first described by Hungerford in 1925. It belongs to the tribe Graptocorixini within the subfamily Corixinae. The species is known to occur in North America, with its specific epithet suggesting a California distribution. Water boatmen in this family are aquatic insects found in freshwater habitats.
Graptocorixa serrulata
Graptocorixa serrulata is a species of water boatman (family Corixidae) in the order Hemiptera. It is a small aquatic true bug distributed across parts of North America and Middle America. As a member of the Graptocorixini tribe, it inhabits freshwater environments where it likely occupies the benthic zone typical of corixid beetles. The species was described by Philip Reese Uhler in 1897.
Gyretes torosus
Gyretes torosus is a species of whirligig beetle in the family Gyrinidae. The species was described from North America in 2004. As a member of Gyretes, it belongs to a genus that is common in the Ozark region and eastern North America. Like other whirligig beetles, it is presumed to inhabit the surface of freshwater bodies. The specific epithet 'torosus' refers to a muscular or bulging appearance, likely describing some aspect of the species' morphology.
Gyrinus maculiventris
whirligig beetle
Gyrinus maculiventris is a species of whirligig beetle in the family Gyrinidae. It inhabits freshwater surface habitats in North America. Like other members of its genus, it exhibits the characteristic rapid, erratic circling behavior on water surfaces that gives whirligig beetles their common name.
Gyrinus pectoralis
whirligig beetle
Gyrinus pectoralis is a species of whirligig beetle in the family Gyrinidae, first described by LeConte in 1868. It is found across North America, with records from Canada (Alberta, British Columbia, Labrador) and presumably throughout much of the United States. Like other whirligig beetles, it inhabits the surface waters of freshwater systems.
Gyrinus plicifer
whirligig beetle
Gyrinus plicifer is a species of whirligig beetle in the family Gyrinidae. It occurs in North America, with records from British Columbia, Canada. Like other members of the genus, it inhabits the surface of freshwater bodies where it forms aggregations. The species was described by LeConte in 1852.
Gyrinus pugionis
whirligig beetle
Gyrinus pugionis is a species of whirligig beetle in the family Gyrinidae, found in North America. Like other members of the genus, it inhabits the surface of freshwater bodies where it exhibits characteristic erratic, circular swimming patterns. The species was described by Fall in 1922. Specific details regarding its biology and ecology remain limited in published literature.
Hadziidae
Hadziidae is a family of amphipod crustaceans established by S. Karaman in 1943. Members are taxonomically difficult to distinguish from the closely related family Melitidae. The family includes both marine and freshwater-dwelling species, with some lineages having colonized subterranean habitats.
Halesochila
Halesochila is a monotypic genus of northern caddisflies in the family Limnephilidae, containing the single described species H. taylori. The genus was established by Banks in 1907. As a member of Limnephilidae, it belongs to a diverse family of case-making caddisflies commonly found in freshwater habitats.
Haliplidae
Crawling Water Beetles, haliplids
Haliplidae is a family of small aquatic beetles comprising approximately 200 species in five genera, representing the sole extant member of the superfamily Haliploidea. These beetles are characterized by their distinctive swimming behavior using alternating leg movements, which renders them relatively clumsy swimmers compared to other aquatic beetles. Consequently, they predominantly move by crawling along substrates rather than swimming. The family exhibits a cosmopolitan distribution in freshwater habitats worldwide.
Haliplus borealis
Haliplus borealis is a small aquatic beetle in the family Haliplidae, commonly known as crawling water beetles. The species occurs in North America with confirmed records from Alberta and Manitoba in Canada. Like other members of its genus, it inhabits freshwater environments. The species was described by LeConte in 1850. Available information on this species is limited, with only five observations documented on iNaturalist.
Haliplus cylindricus
Haliplus cylindricus is a species of crawling water beetle in the family Haliplidae, described by Roberts in 1913. The species belongs to a genus of small aquatic beetles commonly found in freshwater habitats. Very few observations of this species have been documented, with only two records in iNaturalist as of the available data. Like other haliplids, it is presumed to inhabit shallow, vegetated waters where it feeds on algae and small aquatic organisms.
Haliplus fulvus
Haliplus fulvus is a species of crawling water beetle in the family Haliplidae, widely distributed across Europe and North America. Adults are small beetles measuring 3.8–4.2 mm in length. The species is associated with aquatic habitats and has a holarctic distribution pattern.
Haliplus gracilis
crawling water beetle
Haliplus gracilis is a species of crawling water beetle in the family Haliplidae, described by Roberts in 1913. The species belongs to a genus of small aquatic beetles commonly found in freshwater habitats. Like other haliplids, it is adapted to life in and around water, with morphology suited for crawling rather than swimming.
Haliplus leopardus
Haliplus leopardus is a crawling water beetle in the family Haliplidae, first described by Roberts in 1913. The species is recorded from eastern North America, with confirmed observations in New Brunswick and Nova Scotia, Canada. As a member of Haliplidae, it inhabits freshwater environments. Very few observations of this species have been documented, with only three records in iNaturalist as of the knowledge cutoff.
Haliplus parvulus
Haliplus parvulus is a species of crawling water beetle in the family Haliplidae. Members of this genus are small, semi-aquatic beetles associated with freshwater habitats. Very few observations of this species exist in public databases.
Haliplus stagninus
Haliplus stagninus is a species of crawling water beetle in the family Haliplidae, described by Leech in 1948. It is known from North America, with records from the Canadian provinces of Alberta and British Columbia. As a member of Haliplidae, it belongs to a family of small aquatic beetles commonly associated with standing or slow-moving freshwater habitats. The species is poorly documented in public sources, with minimal observational data available.
Harpacticoida
Harpacticoid Copepods
Harpacticoida is an order of benthic copepods comprising approximately 463 genera and 3,000 species. Members are predominantly marine but include freshwater families (Ameiridae, Parastenocarididae, Canthocamptidae). They represent the second-largest meiofaunal group in marine sediments after nematodes and are also common in Arctic and Antarctic sea ice. A few species are planktonic or live in association with other organisms.
Helicopsyche
Speckled Peter, Spiral Caddisflies
Helicopsyche is a genus of caddisflies (Trichoptera: Helicopsychidae) containing more than 230 species with highest diversity in tropical and sub-tropical regions. The genus is represented on all major faunal regions worldwide. Larvae construct distinctive helical, snail-shell-like cases from sand grains and silk. Adults are known to fly fishers as the 'Speckled Peter'. The genus was first described by Siebold in 1856.
Helicopsyche borealis
Spectacled Snail-case Caddisfly
Helicopsyche borealis is a caddisfly species in the family Helicopsychidae, notable as one of only two Helicopsyche species to colonize temperate North America from a predominantly tropical genus. Larvae construct distinctive spiral, snail-like cases from sand grains cemented with silk. The species inhabits running waters across North America and plays a role as a collector-gatherer and scraper in stream ecosystems. Adults emerge in spring, and the life cycle is univoltine with egg diapause through summer.
Helicopsychidae
Snail-case Caddisflies
Helicopsychidae, commonly known as snail-case caddisflies, is a family of Trichoptera characterized by larvae that construct distinctive spiral, helix-shaped cases resembling snail shells. The family contains over 230 species distributed across all major faunal regions, divided into two genera: the monophyletic Rakiura and Helicopsyche. The subgenus Cochliopsyche is endemic to the Neotropical region between central Uruguay and southern Mexico. Species inhabit diverse freshwater environments including springs, streams, and rivers.
Helophoridae
water scavenger beetles, crawling water beetles
Helophoridae is a family of small aquatic beetles within the superfamily Hydrophiloidea, containing the single genus Helophorus. The family comprises approximately 191 species distributed primarily across the Holarctic region, with 150 species in the Palearctic and 41 in North America. A limited number of species occur in the Afrotropical region (six species), Central America, and the Indomalayan region (one species in northern India). Species inhabit diverse freshwater habitats including springs, ponds, temporary pools, and running waters, with many showing strong associations with specific hydrological regimes.
Heptagenia pulla
dusky flat-headed mayfly
Heptagenia pulla is a species of flat-headed mayfly in the family Heptageniidae, commonly known as the dusky flat-headed mayfly. The species was described by Clemens in 1913 and is native to the Nearctic region. Like other members of its genus, it is associated with flowing freshwater habitats. The specific epithet "pulla" refers to the dusky or dark coloration characteristic of this species.
Hesperocorixa atopodonta
water boatman
Hesperocorixa atopodonta is a species of water boatman described by Hungerford in 1927. It belongs to the family Corixidae, a group of aquatic true bugs known for their oar-like hind legs adapted for swimming. The species is native to North America and is part of the genus Hesperocorixa, which includes several similar aquatic insect species.
Hesperocorixa interrupta
Hesperocorixa interrupta is a species of water boatman in the family Corixidae, first described by Thomas Say in 1825. It belongs to a genus of aquatic true bugs distributed across North America. Water boatmen in this family are characterized by their oar-like hind legs adapted for swimming and their aquatic lifestyle in freshwater habitats.
Hesperocorixa kennicottii
Hesperocorixa kennicottii is a species of water boatman in the family Corixidae. It is a small aquatic true bug found in North American freshwater habitats. The species was described by Philip R. Uhler in 1897. Like other members of the genus Hesperocorixa, it is adapted to life in lentic and slow-moving waters.
Hesperocorixa laevigata
water boatman
Hesperocorixa laevigata is a species of water boatman (family Corixidae) described by Uhler in 1893. It is distributed across Central America and North America. As a member of the Nepomorpha, it is an aquatic true bug adapted to life in freshwater environments. The species is one of approximately 47 observed records on iNaturalist, indicating it is documented but not extensively studied.
Hesperocorixa lucida
Hesperocorixa lucida is a species of water boatman in the family Corixidae, described by Abbott in 1916. The species is recorded from North America and belongs to a genus of aquatic true bugs commonly found in freshwater habitats. Like other corixids, it is adapted to life in water with oar-like hind legs modified for swimming.
Hesperocorixa michiganensis
Hesperocorixa michiganensis is a species of water boatman (family Corixidae) described by Hungerford in 1926. It belongs to a genus of aquatic true bugs found in freshwater habitats. The species is recorded from North America, specifically within the Nearctic region. Like other Corixidae, it is adapted to underwater life with modified hind legs for swimming.
Hesperocorixa semilucida
Hesperocorixa semilucida is a species of water boatman in the family Corixidae, described by Walley in 1930. It belongs to a genus of aquatic true bugs found in freshwater habitats. The species is documented from North America. Like other Corixidae, it is an aquatic insect adapted to life in ponds, lakes, and slow-moving waters.
Hesperoperla hoguei
Banded Stone
Hesperoperla hoguei is a species of stonefly in the family Perlidae, commonly known as the banded stone. It is a member of the subfamily Acroneuriinae, a group of predatory stoneflies often associated with flowing freshwater habitats. The species was described by Baumann and Stark in 1980 and is known from western North America, particularly California. As with other perlid stoneflies, it likely inhabits cool, well-oxygenated streams.
Hesperophylax
Hesperophylax is a genus of northern caddisflies (Trichoptera: Limnephilidae) comprising seven described species distributed across western North America. The genus is characterized by morphological plasticity and broad habitat tolerance compared to other Trichoptera. Larvae construct portable protective cases and exhibit chemically-mediated antipredator behaviors. All species appear to be univoltine with extended adult flight periods.
Heterelmis obscura
Heterelmis obscura is a species of riffle beetle in the family Elmidae, first described by Sharp in 1882. It inhabits freshwater environments in Central and South America. Like other elmid beetles, it is fully aquatic throughout its life cycle, with adults possessing a plastron—a layer of air trapped by body hairs that enables underwater respiration.
Heterocheilidae
half-bridge flies
Heterocheilidae is a family of parasitic nematodes (phylum Nematoda) within the order Rhabditida and infraorder Ascaridomorpha. Members are intestinal parasites primarily infecting fish hosts, including elasmobranchs and teleosts. The family includes genera such as Brevimulticaecum, Ortleppascaris, and Dujardinascaris. Notably, the name 'Heterocheilidae' has also been applied to a family of dipteran insects (true flies), but this usage is taxonomically distinct and not accepted in current nematode classification.
Heterocloeon curiosum
curious small minnow mayfly
Heterocloeon curiosum is a small minnow mayfly in the family Baetidae, native to North America. It has been studied in Virginia river systems, where it demonstrates bivoltine life history with two summer generations. Reservoir construction with surface release can significantly alter its emergence timing, larval density, and fecundity through thermal regime changes.
Holopedium
water flea
Holopedium is the sole genus in the family Holopediidae, comprising approximately seven described species of planktonic cladocerans commonly known as water fleas. These crustaceans are distinguished by a gelatinous capsule surrounding the body, which serves as an inducible defense against predation. Species within this genus exhibit notable phenotypic plasticity in body size, capsule dimensions, and reproductive investment in response to predation pressure and food availability. The genus has been studied extensively for its population dynamics, predator-prey interactions, and responses to environmental stressors in freshwater lake systems.
Holopedium gibberum
Holopedium gibberum is a planktonic cladoceran distinguished by a large gelatinous mantle that encloses the body. The species exhibits pronounced phenotypic plasticity in mantle size as an inducible defense against invertebrate predators, particularly Chaoborus larvae. Populations show strong sensitivity to fish predation pressure, with distribution patterns reflecting avoidance of high-predation environments. The species demonstrates seasonal population dynamics tied to food availability and predation regimes, with reproductive investment varying in response to environmental stressors.
Holopedium glacialis
A small freshwater cladoceran crustacean in the family Holopediidae. The species was described in 2007 from Nearctic material and is distinguished from congeners by genetic and morphological characteristics. Like other members of the genus, it possesses a distinctive gelatinous mantle that encloses the body.
Homophylax
Homophylax is a genus of caddisflies in the family Limnephilidae, described by Banks in 1900. It belongs to the tribe Chilostigmini within the subfamily Limnephilinae. As a limnephilid genus, its members are associated with freshwater habitats where larvae construct protective cases. The genus is poorly documented in public sources, with minimal observational records available.
Huleechius
Huleechius is a genus of riffle beetles in the family Elmidae, established by Brown in 1981. The genus contains at least two described species: Huleechius marroni and Huleechius spinipes. Like other elmids, these beetles are associated with freshwater habitats, particularly flowing water environments.
Huleechius marroni
Huleechius marroni is a species of riffle beetle (family Elmidae) described by Brown in 1981. It belongs to the genus Huleechius, a group of aquatic beetles adapted to flowing water habitats. The species is known from Middle America and North America. Like other elmids, it is presumed to inhabit freshwater streams and rivers, though specific ecological details remain poorly documented.
Husseyella turmalis
Husseyella turmalis is a small water strider in the family Veliidae, originally described as Microvelia turmalis by Drake & Harris in 1933. It belongs to the subfamily Microveliinae, a group of minute semiaquatic bugs that inhabit the surface film of freshwater habitats. The genus Husseyella is a small group within the Veliidae, and this species appears to have a limited number of documented observations.
Hyalella
Hyalella is a genus of freshwater amphipods found in the Americas, with species distributed across North, Central, and South America. The genus contains numerous endemic species, particularly in South America, and includes the widely studied H. azteca, which serves as a standard test organism in aquatic toxicology. Members occupy benthic habitats in lakes, streams, and springs, where they function as important components of freshwater food webs.
Hyalella azteca
scud, freshwater scud
Hyalella azteca is a widespread and abundant amphipod crustacean in North America, reaching 3–8 mm in length. It inhabits fresh and brackish waters across a broad geographic range from Central America to the Arctic tree line. The species is a significant food source for waterfowl and serves as a standard test organism in aquatic ecotoxicology and sediment toxicity assessments.
Hyalella wellborni
Hyalella wellborni is a freshwater amphipod species in the family Hyalellidae, described in 2015 from the southeastern United States. The genus Hyalella comprises small benthic crustaceans commonly known as scuds or sideswimmers, widespread in lakes, ponds, and streams. H. wellborni represents part of a taxonomically complex group where species delineation has historically relied on morphological and molecular analyses. The species is known from a limited number of observations, reflecting both its relatively recent description and the ongoing challenges in amphipod taxonomy.
Hydaticini
Hydaticini is a tribe of diving beetles (family Dytiscidae, subfamily Dytiscinae) established by Sharp in 1880. Members of this tribe are aquatic predators found in freshwater habitats. The tribe includes the genus Hydaticus, with species documented from the Neotropics including the Amazon basin and Brazilian highlands.
Hydaticus
Hydaticus is a genus of predatory diving beetles in the family Dytiscidae, comprising approximately 150 described species and 12 subspecies arranged in two subgenera: Hydaticus and Prodaticus. The genus has a cosmopolitan distribution spanning the Palearctic, Afrotropical, Nearctic, and Oriental regions. Members are aquatic predators found in freshwater habitats including streams, pools, and lentic environments.
Hydaticus cinctipennis
Hydaticus cinctipennis is a predaceous diving beetle in the family Dytiscidae. The species has been documented in North America and the Caribbean. As a member of the genus Hydaticus, it belongs to a group of aquatic beetles adapted to freshwater environments.
Hydaticus rimosus
Hydaticus rimosus is a diving beetle species in the family Dytiscidae, first described by Aubé in 1838. The species belongs to the genus Hydaticus, a group of predatory aquatic beetles commonly found in freshwater habitats. It occurs in the Caribbean and Middle America based on documented distribution records.
Hydatophylax
northern caddisfly
Hydatophylax is a genus of northern caddisflies (Trichoptera: Limnephilidae) comprising approximately 14 described species. Members are found in cool temperate regions of the Northern Hemisphere, including Scandinavia, Japan, and North America. The genus exhibits univoltine life cycles with larval development in freshwater streams.