Aquatic
Guides
Dryopidae
long-toed water beetles
Dryopidae is a family of aquatic beetles in the superfamily Byrrhoidea, commonly known as long-toed water beetles. Adults possess dense hydrofuge hairs that enable underwater respiration and extended claws that give the family its common name. Despite being aquatic, adults cannot swim and instead cling to floating detritus. The family is distinguished from similar riffle beetles (Elmidae) by antennae that are not clubbed. Most species have terrestrial larvae, though the genus Stygoparnus has fully aquatic larvae and adults.
Dryops
long-toed water beetles
Dryops is a genus of long-toed water beetles in the family Dryopidae, with at least 20 described species and a worldwide distribution. The genus is particularly diverse in the Palaearctic region, where 34 species have been recorded. Members of this genus are aquatic beetles associated with freshwater habitats. Species such as Dryops rufipes and Dryops renateae have been documented from Turkey and Tajikistan respectively.
Dubiraphia giulianii
Giuliani's Dubiraphian Riffle Beetle
Dubiraphia giulianii is a species of riffle beetle (family Elmidae) described by Van Dyke in 1949. Like other elmid beetles, it is adapted to life in flowing water environments. The species is known from North America, though detailed biological information remains limited.
Dubiraphia harleyi
Dubiraphia harleyi is a species of riffle beetle in the family Elmidae, described by Barr in 1984. Riffle beetles are aquatic beetles that inhabit flowing water environments. The species is known from North America.
Dytiscidae
predaceous diving beetles, diving beetles
Dytiscidae, the predaceous diving beetles, is a family of aquatic beetles containing over 4,000 described species. Adults range from 0.9 mm to 4.75 cm in length, with most species between 1–2.5 cm. They are characterized by enlarged, flattened hind legs adapted for swimming and a streamlined, oval body shape that reduces drag underwater. The family exhibits remarkable chemical ecology, producing unique defensive steroids found nowhere else in the animal kingdom. Larvae, known as "water tigers," are elongate predators with sharp, pincer-like mandibles that inject digestive enzymes into prey.
Dytiscus
predaceous diving beetles
Dytiscus is a Holarctic genus of large predaceous diving beetles comprising 26 species. Adults range 2.2–4.4 cm in length and are fully aquatic, breathing air collected under their elytra. Both adults and larvae are active predators. The genus has been observed to reduce mosquito larva populations in wetland habitats.
Dytiscus fasciventris
Understriped Diving Beetle
Dytiscus fasciventris, the Understriped Diving Beetle, is a predaceous diving beetle in the family Dytiscidae. The species is found in North America, with records from Canada (Alberta, British Columbia) and the United States. Like other members of the genus Dytiscus, it is an aquatic predator inhabiting freshwater environments.
Dytiscus harrisii
Harris's diving beetle
Dytiscus harrisii, commonly known as Harris's diving beetle, is a predaceous diving beetle in the family Dytiscidae. It is one of the larger diving beetle species in North America. As a member of the genus Dytiscus, it is an aquatic predator inhabiting freshwater systems.
Dytiscus hybridus
Hybrid Predaceous Diving Beetle
Dytiscus hybridus is a species of predaceous diving beetle in the family Dytiscidae. It is found in North America, with confirmed records from Alberta and Manitoba in Canada. As a member of the genus Dytiscus, it is an aquatic predator, though specific details of its biology remain poorly documented in published sources.
Dytiscus marginicollis
giant green water beetle
Dytiscus marginicollis, commonly known as the giant green water beetle, is a predaceous diving beetle in the family Dytiscidae. It is among the larger species in the genus Dytiscus and is distributed across North America. Like other members of its genus, it is an aquatic predator inhabiting freshwater systems.
Elmidae
Riffle beetles
Elmidae, commonly known as riffle beetles, is a family of aquatic beetles in the superfamily Byrrhoidea containing over 150 genera and 1,500 described species. Both adults and larvae are primarily aquatic, inhabiting fast-flowing shallow areas of streams and rivers such as riffles. Adults breathe underwater using a plastron—a microfilm of air held by microscopic hairs on their body surface that enables oxygen diffusion from the water. The family has significant value in freshwater biomonitoring due to their sensitivity to water pollution.
Elminae
riffle beetles
Elminae is a subfamily of riffle beetles (family Elmidae) comprising at least 120 genera and over 1,300 described species. Members are primarily aquatic, inhabiting running water habitats across all major biogeographic regions. The subfamily exhibits considerable morphological diversity, with some genera showing pronounced secondary sexual dimorphism and miniaturization traits.
Elmini
riffle beetles
Elmini is a tribe of riffle beetles within the family Elmidae, comprising over 90 genera and approximately 1,200 described species in North America. These beetles are strictly aquatic as adults and larvae, inhabiting flowing water systems. The tribe represents a major radiation within the Elmidae, with species diversity concentrated in freshwater habitats.
Enallagma carunculatum
Tule Bluet
Enallagma carunculatum, commonly known as the tule bluet, is a species of damselfly in the family Coenagrionidae. It is native to North America and belongs to a genus that has been intensively studied by odonatologists, including taxonomic revisions by Rosser Garrison in 1984. As a member of the narrow-winged damselflies, it shares characteristics typical of the genus Enallagma, including slender bodies and aquatic larval stages. The species name 'carunculatum' refers to a small fleshy protuberance, likely describing a distinctive morphological feature.
Estelloxus
Estelloxus is a genus of mites in the family Lebertiidae, order Trombidiformes. The genus was established by Habeeb in 1963 and belongs to the superfamily Lebertioidea. Members of this genus are predatory or parasitic mites associated with freshwater or semi-aquatic habitats. The genus is poorly known, with limited published information on species diversity and biology.
Eubriinae
Eubriinae is a cosmopolitan subfamily of water penny beetles (Psephenidae) comprising approximately 15 genera and 144 species, with greatest diversity in Asia. Adults are distinguished by a convex dorsal body form, truncate or emarginate anterior pronotum with exposed head, non-tapering maxillary palpus apex, and five abdominal ventrites. Larvae are aquatic and exhibit a metapneustic respiratory system with spiracles positioned near the bases of paratergites VIII. The subfamily exhibits nearly worldwide distribution except Antarctica and some oceanic islands including New Zealand.
Eugaurax
frit flies
Eugaurax is a genus of frit flies (Chloropidae) established by Malloch in 1913. The genus contains 11 New World species, with North American representatives including leaf miners of aquatic plants. Larvae of E. floridensis mine tissues of arrowheads (Sagittaria spp.), while E. hydrocotyles is a leaf and stem miner of floating marshpennywort (Hydrocotyle ranunculoides). A species complex centered on E. quadrilineatus occurs throughout the Americas but its larval biology remains largely unknown.
Eurypterida
sea scorpions, eurypterids
Eurypterida is an extinct order of aquatic chelicerate arthropods commonly known as sea scorpions. They ranged from the Cambrian through the Permian periods, with their main diversification occurring during the Paleozoic. The group includes both marine and freshwater species, with body sizes ranging from a few centimeters to over two meters in some species. Eurypterids are characterized by a segmented body with a prosoma and opisthosoma, paired swimming paddles, and a terminal telson spine. They represent one of the largest arthropod groups in the fossil record and are significant for understanding early chelicerate evolution.
Eylais
Eylais is a genus of water mites in the family Eylaidae. The genus has cosmopolitan distribution. Larvae are ectoparasites of diving beetles (family Dytiscidae), attaching primarily to the ventral surface of the hindwings beneath the elytra.
Globia oblonga
Oblong Sedge Borer Moth, oblong sedge borer
Globia oblonga is a noctuid moth commonly known as the oblong sedge borer. First described by Grote in 1882, this species was formerly placed in the genus Capsula before that name was abandoned due to a homonym conflict with a mollusk genus. The species is notable for its specialized larval biology: early instars are leaf miners on emergent aquatic plants, while later instars transition to stem-boring below the water line. Adults are medium-sized moths with wingspans of 35–50 mm.
Gomphurus hybridus
Cocoa Clubtail
A medium-sized clubtail dragonfly endemic to eastern North America. Adults are active in late spring through mid-summer, with peak emergence typically in June. The species is named for the cocoa-brown coloration of mature males. Larvae develop in streams and rivers, requiring clean, flowing water with sandy or gravelly substrates. Like other gomphids, it is a predator both as aquatic nymph and aerial adult.
Gonielmis
Gonielmis is a genus of riffle beetles (family Elmidae) described by Sanderson in 1954. These beetles are aquatic insects associated with flowing water habitats. The genus belongs to the tribe Elmini within the subfamily Elminae. Taxonomic status varies between sources, with some treating it as a synonym of Heterlimnius while others recognize it as valid.
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.
Gyrinidae
Whirligig Beetles
Whirligig beetles (family Gyrinidae) are aquatic beetles that inhabit the surface film of freshwater habitats worldwide. The family comprises approximately 700 extant species in 15 genera. These beetles are instantly recognizable by their habit of swimming rapidly in circles on the water surface when alarmed, a behavior that gives them their common name. They possess divided compound eyes—upper portions adapted for vision above water and lower portions for underwater viewing—a unique adaptation among insects. Members of this family are active predators and scavengers that form conspicuous aggregations or "rafts" on the water surface, which serve defensive functions through enhanced predator detection and possible aposematic signaling.
Gyrinus
whirligig beetle
Gyrinus is a genus of small aquatic beetles in the family Gyrinidae, commonly known as whirligig beetles. Members are strictly aquatic and live almost exclusively on the water surface, where they form conspicuous aggregations called rafts. They are native to multiple biogeographic regions including the Palearctic, Nearctic, North Africa, Asia, and Australia. The genus is distinguished from the larger Dineutus by its smaller size, exposed scutellum, and more pointed elytral apices.
Gyrinus gehringi
whirligig beetle
Gyrinus gehringi is a species of whirligig beetle in the family Gyrinidae, described by Chamberlain in 1929. The species is known from North America, with records from Canada including New Brunswick, Newfoundland, and Nova Scotia. Whirligig beetles in this genus are small to medium-sized aquatic beetles that live on the water surface, where they form conspicuous aggregations and exhibit rapid, erratic swimming behavior.
Gyrinus gibber
whirligig beetle
Gyrinus gibber is a species of whirligig beetle (family Gyrinidae) described by LeConte in 1868. Like other members of its family, it inhabits the water surface of freshwater habitats. The species occurs in North America, with records from Canada (New Brunswick, Ontario, Québec) and the United States. Whirligig beetles are named for their characteristic rapid, circling swimming patterns on water surfaces.
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 minutus
whirligig beetle
Gyrinus minutus is a small whirligig beetle with a Holarctic distribution spanning northern North America and Eurasia. It is distinguished from congeners by its weak swimming ability, solitary behavior among emergent vegetation, and near-absence of volatile defensive compounds. The species exhibits a shortened life cycle of approximately seven weeks from egg to adult and is capable of flight, allowing colonization of new water bodies throughout the summer.
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 picipes
whirligig beetle
Gyrinus picipes is a species of whirligig beetle in the family Gyrinidae. It is found in North America, with records from multiple Canadian provinces including Alberta, British Columbia, and Manitoba. Whirligig beetles in this genus are characterized by their distinctive habit of swimming in erratic, circling patterns on the water surface.
Gyrinus pleuralis
whirligig beetle
Gyrinus pleuralis is a species of whirligig beetle described by Fall in 1922. It is found in North America, with records from Canada (Alberta, British Columbia, Saskatchewan) and presumably the United States. As a member of the family Gyrinidae, it is an aquatic beetle that lives on the water surface, though specific details of its biology are poorly documented.
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 wallisi
whirligig beetle
Gyrinus wallisi is a species of whirligig beetle described by Fall in 1922. Members of the genus Gyrinus are small, surface-dwelling aquatic beetles known for their rapid, circular swimming patterns. This species occurs in North America, with records from Canada including Alberta, British Columbia, and Labrador.
Gyrinus woodruffi
whirligig beetle
Gyrinus woodruffi is a species of whirligig beetle in the family Gyrinidae, described by Fall in 1922. It is found in North America. Like other members of the genus Gyrinus, it is a small, aquatic beetle that lives on the water surface in aggregations known as "rafts."
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 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 longulus
crawling water beetle
Haliplus longulus is a species of crawling water beetle in the family Haliplidae. It occurs in North America with confirmed records from western Canada including Alberta and British Columbia. Like other members of Haliplidae, it inhabits aquatic environments. The species was described by LeConte in 1850. Observations remain sparse with only three documented records in iNaturalist.
Haliplus mimeticus
Warm Springs Crawling Water Beetle
Haliplus mimeticus is a small aquatic beetle in the family Haliplidae, commonly known as crawling water beetles. This species was described by Matheson in 1912 and is known from North and Middle America. It is associated with warm spring habitats, as suggested by its common name. The genus Haliplus comprises small beetles that inhabit aquatic environments, often found in vegetation at the margins of ponds, lakes, and slow-moving waters.
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.
Helichus
Helichus is a genus of small beetles in the family Dryopidae, found worldwide except Australia and Antarctica. Adults measure 1–8 mm and inhabit aquatic or riparian environments. The genus is notable for having terrestrial larvae despite the aquatic lifestyle of adults, a trait that may be unique among water-associated insects.
Helichus lithophilus
Contrasted Dryopid
Helichus lithophilus is a species of long-toed water beetle in the family Dryopidae, found in North America. It is commonly known as the Contrasted Dryopid. The species was originally described as Elmis lithophila by Germar in 1824. It belongs to a family of beetles adapted to aquatic and riparian habitats.
Helichus triangularis
Helichus triangularis is a species of long-toed water beetle in the family Dryopidae, described by Musgrave in 1935. The genus Helichus comprises aquatic beetles commonly associated with stream and river habitats. Records indicate presence in North America and Middle America, though specific details about this species' biology remain sparse.
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.
Hemerodromia
dance flies
Hemerodromia is a genus of dance flies (family Empididae) comprising at least 170 described species. Species are primarily associated with lotic freshwater habitats, particularly streams and rivers. Several species show obligate associations with calcareous water systems and tufa formations in limestone karst regions. The genus exhibits high diversity in tropical Southeast Asia, with significant undescribed species richness anticipated.
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 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.