Freshwater
Guides
Neoelmis caesa
riffle beetle
Neoelmis caesa is a species of riffle beetle in the family Elmidae. It is found in North America. As a member of the Elmidae, it inhabits aquatic environments, specifically riffle habitats in streams and rivers. The species was first described by LeConte in 1874.
Neogerris
Neogerris is a genus of water striders in the family Gerridae, established by Matsumura in 1913. The genus comprises approximately 13 described species distributed primarily in the Americas. These insects are adapted to life on the water surface, using their elongated middle and hind legs to skate across ponds, streams, and other freshwater habitats.
Neogerris hesione
Neogerris hesione is a water strider species in the family Gerridae. It inhabits freshwater surfaces across tropical and subtropical regions of the Americas. The species is well-documented with over 1,300 observations on iNaturalist.
Neohermes
Gray Fishflies
Neohermes is a genus of fishflies in the family Corydalidae containing approximately five described species. Species in this genus are aquatic insects associated with freshwater habitats, particularly intermittent streams. The genus is known for including long-lived aquatic species with specialized burrowing behaviors.
Neoleptophlebia memorialis
Neoleptophlebia memorialis is a species of mayfly in the family Leptophlebiidae, originally described by Eaton in 1884. As a member of this family, it belongs to a group of mayflies commonly known as prong-gilled mayflies, characterized by their distinctive gill structures. The species is part of the genus Neoleptophlebia, which contains several North American species. Very few observations of this species have been recorded, suggesting it may be rare, geographically restricted, or underreported.
Neoperla clymene
Coastal Stone
Neoperla clymene, commonly known as the coastal stone, is a stonefly species in the family Perlidae. It occurs in eastern North America, with documented records from Alabama, Florida, Georgia, Illinois, and Indiana. Like other perlid stoneflies, it inhabits freshwater environments where its larvae develop.
Neophylax
autumn mottled sedges
Neophylax is a genus of caddisflies commonly known as autumn mottled sedges, containing more than 30 described species. Larvae are aquatic case-builders that construct protective cases using silk and materials gathered from streambeds, including sand, stones, shells, and plant material. The genus exhibits notable life history diversity, with species showing temporal and spatial segregation in stream systems. Adults typically emerge in autumn, giving rise to the common name.
Neoplea
pygmy backswimmers
Neoplea is a genus of minute aquatic predatory true bugs in the family Pleidae, commonly known as pygmy backswimmers. The genus contains at least 25 described species distributed across North and South America, with numerous undescribed species. Members are small-bodied (approximately 1.5 mm), active predators in lentic freshwater habitats. The best-studied species, Neoplea striola, has been investigated for its potential role in trophic cascades in fishless subtropical ponds.
Neoporus dilatatus
Neoporus dilatatus is a species of predaceous diving beetle in the family Dytiscidae, subfamily Hydroporinae. It is a small aquatic beetle native to North America. The species was originally described as Hydroporus dilatatus by Fall in 1917 and later transferred to the genus Neoporus. Like other members of Dytiscidae, it is adapted to life in freshwater habitats.
Neoporus hebes
Neoporus hebes is a small diving beetle (family Dytiscidae) described by Fall in 1923. As a member of the subfamily Hydroporinae, it inhabits freshwater aquatic environments. The genus Neoporus comprises numerous small dytiscid species found primarily in North America. This species is among the lesser-documented members of the genus, with limited observational records available.
Neoporus lobatus
Neoporus lobatus is a species of diving beetle in the family Dytiscidae, first described by Sharp in 1882. It belongs to the subfamily Hydroporinae, a diverse group of small predatory aquatic beetles. The genus Neoporus comprises small dytiscids found primarily in North America. Like other members of its family, this species is aquatic and occupies freshwater habitats.
Neoporus mellitus
Neoporus mellitus is a small predaceous diving beetle (family Dytiscidae) in the subfamily Hydroporinae. Originally described by LeConte in 1855 as Hydroporus mellitus, the species was later transferred to the genus Neoporus. It is recorded from eastern North America, with confirmed observations in New Brunswick and Ontario, Canada. Like other members of the genus, it inhabits freshwater aquatic environments.
Neoporus vitiosus
Neoporus vitiosus is a small predaceous diving beetle in the family Dytiscidae, subfamily Hydroporinae. The species was described by LeConte in 1855 and is documented from North America, with specific records from Ontario and Québec in Canada. As a member of the Hydroporinae, it likely inhabits freshwater environments, though detailed ecological studies are limited.
Nepa
water scorpion
Nepa is a genus of aquatic true bugs in the family Nepidae, commonly known as water scorpions. These insects inhabit freshwater environments and are characterized by their elongated bodies, raptorial forelegs adapted for capturing prey, and a long respiratory siphon extending from the abdomen. The genus belongs to the subfamily Nepinae and is distinguished from related genera primarily by morphological features of the pronotum and respiratory siphon structure.
Nepidae
waterscorpions, water scorpions, water stick insects, needle bugs
Nepidae is a family of exclusively aquatic predatory true bugs containing approximately 250 species in 14 genera. Members are commonly called waterscorpions due to their superficial resemblance to scorpions, possessing raptorial forelegs and a long caudal respiratory siphon. The family is divided into two subfamilies: Nepinae (broad, flat-bodied 'water scorpions') and Ranatrinae (slender 'water stick insects'). They occur on all continents except Antarctica, inhabiting stagnant or slow-moving freshwater habitats.
Nepomorpha
true water bugs, water bugs
Nepomorpha is an infraorder of aquatic true bugs (Hemiptera: Heteroptera) comprising approximately 2,000 species worldwide. Members are characterized by reduced, weakly muscled antennae typically concealed against the head, and absent or vestigial ocelli. Most species inhabit freshwater environments, with the exception of the superfamily Ochteroidea, which occupies riparian zones along water margins. The group includes diverse forms such as giant water bugs, water scorpions, water boatmen, and backswimmers.
Neureclipsis
tube maker caddisflies
Neureclipsis is a genus of net-spinning caddisflies in the family Polycentropodidae, containing at least eight described species distributed across the Northern Hemisphere and Australia. Larvae construct elaborate silken catchnets to capture drifting invertebrate prey in lotic freshwater habitats. The genus includes the well-studied species N. bimaculata, whose life history and feeding ecology have been investigated in North American and European populations.
Nigronia fasciata
Banded Dark Fishfly
Nigronia fasciata is a species of dark fishfly in the family Corydalidae, order Megaloptera. Adults measure 22–28 mm in body length. The species occurs in the eastern United States and is not present in Canada. Like other fishflies, it has aquatic larval stages and terrestrial adults.
Notomicrus
Notomicrus is a genus of small water beetles in the family Noteridae, first described by Sharp in 1882. Species occur in freshwater habitats across the New World, from North America through Central America to South America and the Caribbean. The genus includes at least 13 described species, with several recent descriptions from Guadeloupe and Suriname. Some species exhibit unusual reproductive traits, including suspected obligate parthenogenesis.
Notonecta
backswimmers, common backswimmer, Milky Backswimmers
Notonecta is a genus of aquatic predatory insects commonly known as backswimmers, comprising approximately 70 species. They are distinguished by their habit of swimming upside down, using long hind legs modified as oars. The genus exhibits distinct morphological and behavioral traits that separate it from superficially similar water boatmen (family Corixidae), including triangular cross-section body shape, bold color patterns, and diurnal activity patterns. Notonecta species occupy diverse freshwater habitats and function as active predators of small aquatic organisms.
Notonecta insulata
backswimmer
Notonecta insulata is a species of backswimmer, an aquatic true bug in the family Notonectidae. It is found in North America, where it inhabits freshwater environments. Like other backswimmers, it swims upside down and is an active predator of small aquatic invertebrates. The species was described by Kirby in 1837.
Notonecta montezuma
Notonecta montezuma is a species of backswimmer in the family Notonectidae. It is an aquatic true bug found in North and Middle America. Like other backswimmers, it swims upside down using its long, oar-like hind legs. The species is part of the genus Notonecta, which contains backswimmers that are generally larger than water boatmen and more commonly encountered in open water habitats.
Notonecta unifasciata andersoni
Notonecta unifasciata andersoni is a subspecies of backswimmer (family Notonectidae) described by Hungerford in 1933. It belongs to the genus Notonecta, a group of aquatic true bugs known for their upside-down swimming posture. The subspecies is part of the widespread N. unifasciata species complex, which occurs across the Americas. As with other notonectids, it is presumed to be an aquatic predator, though specific biological details for this subspecies remain poorly documented in available literature.
Nyctiophylax
Nyctiophylax is a genus of caddisflies in the family Polycentropodidae, established by Brauer in 1865. Species in this genus are small, predatory caddisflies whose larvae construct silken retreats in freshwater habitats. The genus has been documented from Colombia, though its actual distribution likely extends more broadly across the Neotropics. Adults are generally small with reduced wing venation characteristic of the family.
Nymphulini
Nymphulini is a tribe of small moths in the subfamily Acentropinae (Crambidae), characterized by aquatic or semi-aquatic larval habits. The group includes numerous species whose larvae feed on submerged or emergent aquatic plants, making them among the few truly aquatic Lepidoptera. Adults are generally small with narrow wings and reduced mouthparts. The tribe is most diverse in tropical and subtropical regions, with some species extending into temperate zones.
Ochrotrichia
microcaddisfly
Ochrotrichia is a large genus of microcaddisflies (family Hydroptilidae) comprising approximately 226 extant species, making it the most species-rich microcaddisfly genus in the Neotropics. The genus is predominantly distributed in the Nearctic and Neotropical regions, with one exceptional African record from the Democratic Republic of the Congo. Species are primarily found in freshwater stream habitats.
Ochrotrichiinae
microcaddisflies
Ochrotrichiinae is a subfamily of microcaddisflies within the family Hydroptilidae, comprising approximately 430 species across nine genera. The subfamily is most diverse in the Neotropics, with additional representation in the Nearctic and Australasian regions, including an endemic genus in New Caledonia. Phylogenetic analyses support its monophyly with the exclusion of Dibusa. The subfamily originated in the New World during the early Cretaceous, approximately 116 million years ago, with subsequent dispersal to Australasia via trans-Antarctic routes.
Ochteridae
Velvety Shore Bugs
Ochteridae is a small family of true bugs (Hemiptera: Heteroptera: Nepomorpha) comprising approximately 80–90 described species in eight genera. Commonly known as velvety shore bugs, they are semi-aquatic insects inhabiting the margins of freshwater bodies worldwide, with highest diversity in tropical regions. The family is characterized by a velvety body texture, small size (4.5–9 mm), and distinctive antennal and leg sensilla adapted to riparian habitats. Recent taxonomic revisions have significantly expanded the known species diversity, particularly in Australia, Mesoamerica, and the Andes.
Ochterus banksi
velvety shore bug
Ochterus banksi is a species of velvety shore bug in the family Ochteridae, a group of small predatory true bugs associated with moist shoreline habitats. The species was described by Barber in 1913 and is found in North America. A taxonomic revision of the genus Ochterus synonymized O. flaviclavus under O. banksi, recognizing the former as an intraspecific color morph.
Odontoceridae
Mortarjoint Casemaker Caddisflies
Odontoceridae is a family of caddisflies (order Trichoptera) commonly known as mortarjoint casemakers. The family contains approximately 12 genera and at least 100 described species. Larvae are aquatic case-builders that typically construct cases from mineral particles such as sand and small stones. The family has a cosmopolitan distribution with representatives in North America, Europe, South America, and other regions. Adults are generally active during spring and summer months.
Oecetis
long-horned caddisflies
Oecetis is a genus of long-horned caddisflies in the family Leptoceridae, containing over 500 described species worldwide. Adults are distinguished by exceptionally long maxillary palps and an unbranched forewing M vein. Larvae inhabit freshwater environments including lakes, streams, and rivers with sandy substrates. The genus is among the largest and most widely distributed caddisfly genera, occurring in all faunal regions.
Oecetis inconspicua
Inconspicuous Long-horned Caddisfly
Oecetis inconspicua is a species of long-horned caddisfly in the family Leptoceridae. It is found in North America, with additional records from Brazil. The species belongs to a family characterized by larvae that construct portable cases and adults with notably elongated antennae.
Oligoneuriidae
Brushlegged Mayflies, Brushleg Mayflies
Oligoneuriidae is a family of mayflies characterized by specialized filtering structures on their nymphs' forelegs, earning them the common name "brushlegged mayflies." The family exhibits a pantropical distribution with at least 68 described species across over a dozen genera, including both extant and extinct lineages from the Cretaceous period. Nymphs possess two rows of setae on the forelegs used for filter feeding and tufts of gills at the base of their maxillae. The family has been documented from freshwater habitats across Africa, South America, the Mediterranean region, and the Middle East, with some species showing extended multiyear life cycles.
Oligophlebodes
Oligophlebodes is a genus of caddisflies (order Trichoptera) in the family Uenoidae. It was established by German entomologist Georg Ulmer in 1905. The genus belongs to the subfamily Thremmatinae, a group of case-making caddisflies primarily associated with freshwater habitats. Species in this genus are found in the Northern Hemisphere, particularly in Asia and North America.
Oligostomis
giant casemakers
Oligostomis is a genus of giant casemaker caddisflies in the family Phryganeidae, established by Kolenati in 1848. The genus contains at least four described species distributed across the Northern Hemisphere. One species, O. ocelligera, has been documented inhabiting acidic mine drainage environments in Pennsylvania, demonstrating tolerance to extreme pH conditions. Members construct portable cases from plant material, characteristic of the family.
Oligostomis pardalis
Giant casemaker
Oligostomis pardalis is a species of giant casemaker caddisfly in the family Phryganeidae. It is found in North America, where it inhabits freshwater environments. The species was first described by Walker in 1852. Two subspecies are recognized: O. p. pardalis and O. p. redmani.
Optioservus immunis
Optioservus immunis is a species of riffle beetle in the family Elmidae, first described by Fall in 1925. It is one of thirteen Nearctic species in the genus, distinguished from congeners primarily by male genitalia and elytral pattern. The species was previously known under the synonym Optioservus cryophilus.
Optioservus ovalis
Optioservus ovalis is a species of riffle beetle in the family Elmidae, first described by LeConte in 1863. Riffle beetles are aquatic insects whose larvae and adults inhabit running water environments. The species is found in North America, with records from Canada and the United States. Like other elmid beetles, it is likely associated with clean, well-oxygenated streams and rivers.
Optioservus phaeus
Scott optioservus riffle beetle
Optioservus phaeus is a species of riffle beetle (family Elmidae) described by White in 1978. It belongs to a genus of small aquatic beetles inhabiting running waters. The species was described as part of a taxonomic revision based on male genitalia, elytral patterns, and geographic distribution. It is known from a highly restricted range in Kansas.
Orconectes erichsonianus
Erichson's Crayfish
Orconectes erichsonianus is a freshwater crayfish species described by Faxon in 1898, currently classified under the genus Faxonius. The species has been treated as a synonym in modern taxonomic revisions, with its current accepted name being Faxonius erichsonianus. It belongs to the family Cambaridae, a diverse group of North American crayfishes. The species is part of the complex taxonomic history of the genus Orconectes, which has undergone substantial revision based on molecular phylogenetics.
Orconectes limosus
spiny-cheek crayfish
Orconectes limosus, commonly known as the spiny-cheek crayfish, is a freshwater crayfish native to North America that has become a widespread invasive species in Europe. First recorded in Belarus in 1997, it has demonstrated rapid upstream dispersal, spreading 177 km along the Neman River over 14 years. The species is now established in at least 8 river systems across the Neman, Narew and Western Bug basins. Surveys indicate potential competitive displacement of native crayfish species, as no native crayfish have been found co-occurring with O. limosus in invaded areas. The species exhibits notable social behaviors including mother-offspring recognition and kin-preferential interactions.
Orconectes obscurus
Orconectes obscurus is a freshwater crayfish species originally described by Hagen in 1870. It is currently classified as a synonym of Faxonius obscurus following taxonomic revision that transferred species from Orconectes to Faxonius. The species occurs in North America, with distribution records from Canada. Limited specific ecological information is available in the provided sources.
Orconectes propinquus
Northern Clearwater Crayfish
Orconectes propinquus, commonly known as the Northern Clearwater Crayfish, is a freshwater crayfish species in the family Cambaridae. It is native to northern North American clearwater habitats and has been the subject of ecological and physiological research comparing it to other crayfish species. The species shows specific habitat preferences for water depth, velocity, substrate type, and cover availability. It is sensitive to low pH conditions compared to some co-occurring crayfish species.
Orconectes validus
Orconectes validus is a species of freshwater crayfish in the family Cambaridae. The name is currently treated as a synonym of Faxonius validus. Original description dates to 1914 by Faxon. As a synonym, biological information specific to this nominal taxon is limited and may be conflated with the accepted name.
Oreodytes humboldtensis
Oreodytes humboldtensis is a species of predaceous diving beetle in the family Dytiscidae, described by Zimmerman in 1985. As a member of the genus Oreodytes, it belongs to a group of small diving beetles primarily associated with running water habitats. The species epithet suggests a connection to the Humboldt region, likely referring to Humboldt County or the broader Humboldt Bay area of coastal northern California. Like other Oreodytes species, it is presumed to be an aquatic predator in freshwater systems.
Oroperla
Oroperla is a genus of stoneflies in the family Perlodidae, established by Needham in 1933. Members of this genus are classified within the tribe Arcynopterygini and are part of the diverse Systellognatha infraorder. The genus is documented from western North America, specifically California and Nevada. As a perlodid stonefly, it likely inhabits cool, flowing freshwater systems typical of the family.
Osobenus
Osobenus is a genus of stoneflies in the family Perlodidae, first described by Ricker in 1952. The genus belongs to the tribe Diploperlini within the subfamily Perlodinae. Species in this genus are found in western North America, with records from British Columbia, Washington, Oregon, and California.
Osobenus yakimae
Yakima Springfly
Osobenus yakimae is a species of stonefly in the family Perlodidae, commonly known as the Yakima Springfly. It is distributed across the Pacific Northwest of North America, with records from British Columbia, Washington, Oregon, and California. As a member of the order Plecoptera, it is an aquatic insect with nymphal stages developing in freshwater habitats. The species was first described by Hoppe in 1938.
Oulimnius nitidulus
riffle beetle
Oulimnius nitidulus is a species of riffle beetle in the family Elmidae, described by LeConte in 1866. It is distributed across North America. Riffle beetles in this genus are aquatic insects adapted to flowing water environments. The species was originally described under the basionym Elmis nitidula.
Oxyethira
Oxyethira is a genus of microcaddisflies (Trichoptera: Hydroptilidae) comprising over 200 described species worldwide. The genus exhibits high species diversity with new species continuing to be described, particularly from under-sampled regions. Larvae are aquatic and construct distinctive silk cases in their final instar.