Freshwater
Guides
Hydrachna
Hydrachna is a genus of water mites comprising over 80 described species and representing the sole genus in the family Hydrachnidae. These mites are obligate aquatic arachnids found in freshwater habitats. The larvae are ectoparasites of aquatic insects, particularly water beetles and water boatmen, attaching to the thorax and abdomen of hosts. Some host species have developed apparent immunity to parasitism after prolonged exposure.
Hydrachnoidea
water mites
Hydrachnoidea is a superfamily of aquatic mites commonly known as water mites. Members are exclusively freshwater dwellers, representing one of the most diverse radiations of arachnids into aquatic environments. The group includes several families with distinct morphological adaptations for underwater life.
Hydraena americana
Hydraena americana is a species of minute moss beetle in the family Hydraenidae, described by Manfred Jäch in 1993. It belongs to the subgenus Holcohydraena. The species is known from eastern North America, with records from Canada and the northeastern United States. Like other members of its genus, it is an aquatic beetle inhabiting small freshwater habitats.
Hydraena pacifica
Hydraena pacifica is a species of minute aquatic beetle in the family Hydraenidae, first described by Perkins in 1980. The species belongs to the genus Hydraena, commonly known as long-palped water beetles, characterized by their enlarged maxillary palps. It is distributed across western North America from Canada through the western United States. The species epithet 'pacifica' refers to its occurrence in the Pacific region of North America.
Hydraena pensylvanica
Hydraena pensylvanica is a species of minute aquatic beetle in the family Hydraenidae, first described by Kiesenwetter in 1849. Despite its specific epithet suggesting a Pennsylvania origin, this species occurs across eastern North America. Like other members of the genus Hydraena, it inhabits shallow freshwater habitats. The species is poorly documented in recent literature, with only a handful of observations recorded on community science platforms.
Hydrobiomorpha
Hydrobiomorpha is a genus of water scavenger beetles in the family Hydrophilidae, established by Blackburn in 1888. The genus contains 56 extant described species distributed across tropical and subtropical regions, with additional fossil species known from the Cenozoic. Members are aquatic beetles associated with freshwater habitats.
Hydrobiomorpha casta
Hydrobiomorpha casta is a water scavenger beetle in the family Hydrophilidae. The species is distributed across the Caribbean, Central America, and southeastern North America. It is one of approximately 125 species in the genus Hydrobiomorpha, a group of aquatic beetles adapted to freshwater habitats.
Hydrochus callosus
Hydrochus callosus is a species of water scavenger beetle in the family Hydrochidae, first described by John Lawrence LeConte in 1855. The species is found in the southeastern United States, with records from Alabama, Arkansas, Florida, Georgia, Louisiana, Mississippi, South Carolina, and Texas. Hydrochidae are small aquatic beetles typically associated with freshwater habitats.
Hydrocolus
Hydrocolus is a genus of small predaceous diving beetles in the family Dytiscidae, subfamily Hydroporinae. The genus was erected in 2000 to accommodate several species previously placed in related genera, particularly Hydroporus. It contains approximately twelve described species distributed primarily in North America, with some species known from northern Europe. Species are associated with lentic and lotic freshwater habitats.
Hydrocolus stagnalis
Hydroporus Diving Beetle
Hydrocolus stagnalis is a small predaceous diving beetle in the family Dytiscidae, native to North America. Formerly classified under Hydroporus, it was reassigned to the genus Hydrocolus. The species is documented from western Canada, including Alberta and British Columbia. As a member of the Hydroporinae subfamily, it inhabits freshwater environments.
Hydrophilus insularis
Hydrophilus insularis is a water scavenger beetle in the family Hydrophilidae. It is distributed across a broad geographic range from northern South America through the Caribbean, Central America, and Mexico into the southern United States. The species is aquatic and belongs to a genus known for scavenging behavior in freshwater habitats.
Hydroporinae
Hydroporinae is a large subfamily of predaceous diving beetles (family Dytiscidae) containing at least 2,200 described species. Members are primarily aquatic, inhabiting diverse freshwater habitats from lentic pools to lotic streams across all continents except Antarctica. The subfamily exhibits remarkable diversity in body size, with some species among the smallest diving beetles known. Many species are habitat specialists, including stygobiont forms adapted to subterranean waters.
Hydroporini
Hydroporini is a tribe of predaceous diving beetles in the family Dytiscidae, containing at least 730 described species. Members are primarily aquatic, inhabiting freshwater environments including streams, rivers, and groundwater systems. The tribe exhibits a broad geographic distribution spanning Australia, New Guinea, Europe, and other regions, with notable diversity hotspots in south-western Australia.
Hydropsyche alhedra
Hydropsyche alhedra is a species of caddisfly described by Ross in 1939. The species is currently recognized as a synonym of Ceratopsyche alhedra, reflecting taxonomic revisions that have moved this taxon to the genus Ceratopsyche. It belongs to the family Hydropsychidae, a group of net-spinning caddisflies known for constructing capture nets in flowing water.
Hydropsyche betteni
Common Netspinner
Hydropsyche betteni is a species of netspinning caddisfly in the family Hydropsychidae, described by Ross in 1938. It is one of the most widespread and commonly encountered members of its genus in North America. Like other hydropsychids, the larvae construct fixed capture nets to filter food from flowing water. The species is well-documented in freshwater biomonitoring studies due to its abundance and sensitivity to water quality.
Hydropsyche californica
Hydropsyche californica is a species of net-spinning caddisfly (Trichoptera: Hydropsychidae) described by Banks in 1899. It inhabits freshwater benthic environments and has been extensively studied as a bioindicator for metal contamination in aquatic ecosystems, particularly in relation to mine drainage. Research has demonstrated its utility for monitoring cadmium, copper, lead, and zinc exposure in rivers.
Hydropsyche simulans
Hydropsyche simulans is a species of net-spinning caddisfly in the family Hydropsychidae, described by Ross in 1938. Like other members of its genus, it is an aquatic insect whose larvae construct silk nets to capture food in flowing water. The species occurs in North America and is part of the diverse fauna of caddisflies that are ecologically important in freshwater ecosystems and relevant to fly fishing.
Hydropsyche walkeri
Hydropsyche walkeri is a species of net-spinning caddisfly in the family Hydropsychidae. Originally described by Betten and Mosely in 1940, it is currently treated as a synonym of Ceratopsyche walkeri. The species belongs to a diverse genus of aquatic insects whose larvae construct elaborate silk nets to capture food in flowing water. Like other hydropsychids, it is associated with freshwater lotic habitats.
Hydroptila
microcaddisflies
Hydroptila is a large genus of microcaddisflies (family Hydroptilidae) with worldwide distribution. Adults are small, typically collected using ultraviolet light traps near freshwater habitats. Larvae are known as "purse-case makers" that construct portable cases from silk and environmental materials such as filamentous algae. The genus exhibits substantial species diversity, with numerous regional endemics documented across Europe, Asia, and the Americas.
Hydroptila callia
microcaddisfly
Hydroptila callia is a species of microcaddisfly described by Denning in 1948. It belongs to the family Hydroptilidae, the smallest caddisflies, characterized by reduced wing venation and distinctive larval cases. The species is known from North America, with its type locality in the United States. Like other hydroptilids, adults are minute insects typically associated with freshwater habitats.
Hydroptila grandiosa
microcaddisfly
Hydroptila grandiosa is a species of microcaddisfly in the family Hydroptilidae, described by Ross in 1938. As a member of the order Trichoptera, it belongs to a group of aquatic insects closely related to moths and butterflies. The species is recorded from North America. Microcaddisflies in this genus are generally small-bodied and associated with freshwater habitats.
Hydroptila icona
Hydroptila icona is a species of microcaddisfly described by Mosely in 1937. It belongs to the family Hydroptilidae, commonly known as microcaddisflies due to their small size. The species is known from Central America and surrounding regions. Like other members of its genus, it is associated with freshwater habitats. Specific biological details remain poorly documented.
Hydroptila rono
microcaddisfly
Hydroptila rono is a species of microcaddisfly (family Hydroptilidae) described by Ross in 1941. As a member of the order Trichoptera, it is an aquatic insect with larvae that develop in freshwater habitats. The species is known from North America, though specific details about its ecology and biology remain limited in available literature.
Hydroptiloidea
microcaddisflies, purse-case caddisflies
Hydroptiloidea is a superfamily of caddisflies (Trichoptera) containing the family Hydroptilidae. Members are distinguished by their minute size, rarely exceeding 5 mm, and the distinctive purse-shaped larval cases constructed only in the final instar. The group has a worldwide distribution and represents one of the most species-rich lineages within Trichoptera.
Hydrovatus
Hydrovatus is a genus of diving beetles in the family Dytiscidae, subfamily Hydroporinae, and tribe Hydrovatini. The genus comprises approximately 214 species globally, with documented presence across Asia, Europe, and the Americas. Members are aquatic beetles inhabiting lentic and slow-moving lotic freshwater environments. The genus was established by Motschulsky in 1853.
Hydrozetes
Beetle Mites
Hydrozetes is a genus of aquatic oribatid mites (family Hydrozetidae) distinguished by being obligately associated with freshwater habitats. All species in this genus are aquatic, occurring on water surfaces and in benthic zones of lakes, ponds, and other water bodies. The genus has been documented from the Paleocene fossil record through to extant populations across multiple continents. Some species achieve extremely high population densities, dominating benthic invertebrate communities in temporary and permanent water bodies.
Hydrozetidae
Hydrozetidae is a family of aquatic oribatid mites (water mites) within the order Oribatida, established by Grandjean in 1954. The family contains at least one genus, Hydrozetes, with at least 20 described species. These mites are distinguished by adaptations to freshwater habitats, including a reduced bothridium lacking a sensillus, monodactylous legs, and the absence of pteromorphae. Fossil evidence from the Late Paleocene of Canada demonstrates the family's ancient aquatic association with submerged vegetation.
Hydryphantoidea
Hydryphantoidea is a superfamily of prostigmatan mites within Trombidiformes, comprising approximately 250 described species across six families. Members are predominantly aquatic or semiaquatic, inhabiting freshwater habitats worldwide. The group includes the families Hydryphantidae, Hydrodromidae, Rhynchohydracaridae, Thermacaridae, Ctenothyadidae, and Teratothyadidae.
Hygrobatidae
water mites
Hygrobatidae is a family of prostigmatan mites in the order Trombidiformes, commonly known as water mites. The family comprises approximately 78 genera and over 100 described species, though estimates vary. Members are primarily aquatic, inhabiting springs, streams, and running waters across multiple continents. The genus Hygrobates includes a well-studied species complex (fluviatilis-complex) with ten or more morphologically similar species. Some species exhibit parasitic associations with amphibians.
Hygrotini
Hygrotini is a tribe of small diving beetles in the subfamily Hydroporinae. The tribe contains approximately 137 species, most of which inhabit freshwater environments. Multiple lineages have independently evolved tolerance to saline and hypersaline conditions, with some species surviving in concentrations more than double that of seawater.
Hygrotus falli
Hygrotus falli is a diving beetle species in the family Dytiscidae, originally described by Wallis in 1924 under the basionym Coelambus falli. The species belongs to a genus of small to medium-sized predatory diving beetles commonly found in freshwater habitats. As with other members of Dytiscidae, it is likely adapted to aquatic life with modified hind legs for swimming, though specific ecological details for this species remain poorly documented in available sources.
Hygrotus impressopunctatus
Hygrotus impressopunctatus is a small diving beetle in the family Dytiscidae, first described by Schaller in 1783. It belongs to the subfamily Hydroporinae and is native to Europe. The species has been recorded in freshwater habitats. GBIF data indicate potential presence in North America and Southern Asia, though European distribution is best documented.
Hygrotus picatus
Hygrotus picatus is a species of predaceous diving beetle in the family Dytiscidae. It is native to North America and belongs to a genus of small to medium-sized diving beetles commonly found in freshwater habitats. The species was first described by William Kirby in 1837. Like other members of Dytiscidae, it is adapted to aquatic life with streamlined bodies and modified hind legs for swimming.
Hygrotus sellatus
Hygrotus sellatus is a small diving beetle in the family Dytiscidae, described by LeConte in 1866. The species is known from North America, with limited observational records. As a member of the subfamily Hydroporinae, it inhabits freshwater aquatic environments.
Hylogomphus
clubtails
Hylogomphus is a genus of clubtail dragonflies (family Gomphidae) comprising six described species native to eastern North America. The genus was elevated from subgenus status within Gomphus in 2000, reflecting distinct morphological and phylogenetic characteristics. Species within this genus are associated with lotic freshwater habitats and exhibit conservative body plans typical of gomphid dragonflies.
Hylogomphus parvidens
Piedmont Clubtail
Hylogomphus parvidens, the Piedmont Clubtail, is a species of clubtail dragonfly endemic to the southeastern United States. It was transferred from the genus Gomphus to Hylogomphus in 2017 when Hylogomphus was elevated from subgenus to full genus rank. The species inhabits river systems and holds a stable population with no immediate conservation concerns.
Hyporhygma
Hyporhygma is a genus of non-biting midges (Chironomidae) described by Reiss in 1982. As a member of this large dipteran family, adults are characterized by reduced mouthparts and aquatic larval stages. The genus is part of the diverse chironomid fauna found in freshwater habitats worldwide.
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.
Illiesiella
Illiesiella is a genus of stoneflies in the family Leuctridae, commonly known as needleflies or rolled-winged stoneflies. These small, slender insects inhabit cool, clean freshwater environments. The genus was established to accommodate species previously placed in other leuctrid genera based on distinctive morphological characteristics. Members are found in the Holarctic region, with species distributed across Europe and parts of Asia.
Ilybius hypomelas
Ilybius hypomelas is a predaceous diving beetle in the family Dytiscidae, first described by Mannerheim in 1843. This species is part of a genus of small to medium-sized diving beetles commonly found in freshwater habitats. It is known from North America, with specific records from western Canadian provinces including Alberta and British Columbia. As a member of Dytiscidae, it is adapted for aquatic predation.
Ilybius opacus
Ilybius opacus is a predaceous diving beetle in the family Dytiscidae, distributed across North America and the Palearctic region. It is one of numerous species in the genus Ilybius, a group of medium-sized diving beetles typically associated with freshwater habitats. The species was described by Aubé in 1837 and remains a valid, accepted taxon in current classifications.
Ilybius quadrimaculatus
Ilybius quadrimaculatus is a predaceous diving beetle in the family Dytiscidae, first described by Aubé in 1838. The species occurs in North America, with records from Alberta and British Columbia in Canada. As a member of the subfamily Agabinae, it inhabits freshwater aquatic environments where it functions as an active predator.
Ilyocryptus
water fleas
Ilyocryptus is a genus of freshwater cladocerans (water fleas) in the family Ilyocryptidae. Species in this genus are characterized by a benthic lifestyle, inhabiting lake sediments and muddy substrates. The genus has a global distribution with notable diversity in the Neotropics and Far East. Several species groups have been identified, including the widespread I. spinifer group and the sarsi-group, with some taxa showing complex biogeographic patterns across transitional zones between boreal and tropical regions.
Insecta
Insects
Insects constitute the largest and most diverse class of arthropods, comprising more than one million described species with estimates of total species ranging from 2 to 30 million. They are characterized by a three-part body plan (head, thorax, abdomen), three pairs of jointed legs, compound eyes, and one pair of antennae. Insects occupy virtually every terrestrial and freshwater habitat, and many have colonized marine environments. Their ecological dominance stems from extraordinary diversity in form, function, and life history strategies.
Integripalpia
Integripalpia is a suborder of caddisflies (Trichoptera) distinguished by adults having unringed terminal segments on their maxillary palps. Larvae are aquatic and construct portable protective cases from debris beginning in the first instar, enlarging them through subsequent developmental stages. Case construction is often highly specific, with distinctive architectural patterns characteristic of particular families and genera. The suborder includes diverse lineages distributed across aquatic habitats worldwide.
Ischnura demorsa
Mexican Forktail
Ischnura demorsa, commonly known as the Mexican Forktail, is a narrow-winged damselfly in the family Coenagrionidae. It is a small, slender species found in freshwater habitats across Central America and the southwestern United States. The species is classified as Least Concern by the IUCN, with a stable population and no immediate threats to its survival. It is frequently observed in association with springs and rivers with emergent vegetation.
Ischnura posita
fragile forktail
Ischnura posita, commonly known as the fragile forktail, is a small damselfly species in the family Coenagrionidae. It measures 21–29 mm in body length and is native to most of eastern North America. The species is one of the more common damselflies along the east coast of the United States and is readily identified by distinctive exclamation mark-shaped shoulder stripes present in both sexes.
Ischnura verticalis
Eastern Forktail
Ischnura verticalis, the Eastern Forktail, is a small damselfly in the family Coenagrionidae. Larvae exhibit behavioral thermoregulation through depth selection in water columns, moving deeper at higher temperatures and shallower when cooler. Development is temperature- and prey-dependent, with faster development at higher temperatures and food availability. Males typically develop faster than females, with sexual differences in larval behavior and instar progression. Adults emerge over extended periods, with univoltine life cycles in temperate populations.
Isonychia intermedia
Isonychia intermedia is a species of mayfly in the family Isonychiidae. Like other members of its genus, it is an aquatic insect with a life cycle consisting of an extended nymphal stage in freshwater habitats followed by a brief adult stage. The species is found in North America and is part of the EPT (Ephemeroptera-Plecoptera-Trichoptera) assemblage used in water quality biomonitoring. Adults are known to anglers as 'slate drakes' due to their dark wing coloration.
Isonychia rufa
Isonychia rufa is a brushlegged mayfly species in the family Isonychiidae, first described by McDunnough in 1931. It belongs to the bicolor group within its genus. The species is found in larger rivers and streams of the Mississippi drainage system in central North America.