Mayfly
Guides
Hexagenia bilineata
Emergent Mayfly
Hexagenia bilineata is a burrowing mayfly native to the Upper Mississippi Valley of North America. The aquatic nymphs construct U-shaped burrows in mud and silt, filtering organic detritus for food. Adults emerge synchronously in enormous numbers during summer evenings, creating spectacular swarms that have caused documented traffic hazards and infrastructure damage. The species exhibits mixed voltinism, with some populations completing development in one year while others require two years.
Hexagenia rigida
Great Olive-winged Drake
Hexagenia rigida is a burrowing mayfly (Ephemeroptera: Ephemeridae) native to North America. As a member of the common burrower mayfly genus, it spends most of its life as an aquatic nymph in lake and reservoir sediments, with adults emerging synchronously in large swarms. The species has a multi-year life cycle, typically requiring 3-4 years to complete development from egg to adult in northern climates. Laboratory studies indicate that larval growth and mortality are significantly influenced by food availability and density, with food limitation increasing size variation and mortality rates.
Homoeoneuria alleni
Homoeoneuria alleni is a species of mayfly (Ephemeroptera) in the family Oligoneuriidae, described by Pescador & Peters in 1980. The genus Homoeoneuria is part of the heptagenioid lineage of mayflies. This species is known from the Nearctic region, with records from North America and Middle America.
Ironodes
Ironodes is a genus of mayflies in the family Heptageniidae, first described by Traver in 1935. Members of this genus are part of the diverse Heptageniidae family, commonly known as flat-headed mayflies due to their distinctive head morphology. The genus is represented by relatively few observations, suggesting it may be uncommon, geographically restricted, or underreported in surveys.
Ironodes nitidus
Ironodes nitidus is a species of flat-headed mayfly in the family Heptageniidae. The species was described by Eaton in 1885. It belongs to a genus of mayflies found in North America, with records from the Nearctic region including Middle America and North America. The genus Ironodes is part of the diverse Heptageniidae family, which contains many species adapted to running water habitats.
Isonychia
Slate Drakes, Brushlegged Mayflies
Isonychia is a genus of mayflies comprising over 30 described species, commonly known as Slate Drakes or brushlegged mayflies. The genus is the sole member of the family Isonychiidae. Nymphs are notable for possessing raptorial forelegs adapted for predation, a trait uncommon among mayflies. Some species exhibit habitat generalist ecology while others are specialized to intermittent streams.
Isonychia arida
arid howdy mayfly
Isonychia arida is a species of brushlegged mayfly in the family Isonychiidae. It was described by Thomas Say in 1839, originally as Baetis arida. The species is found in North America and is known by the common name "arid howdy mayfly." Like other members of the genus Isonychia, it belongs to a group commonly referred to as "slate drakes" by anglers.
Isonychia bicolor
mahogany dun
Isonychia bicolor, commonly known as the mahogany dun, is a species of brushlegged mayfly in the family Isonychiidae. It is found in southeastern Canada and the eastern United States. Like all mayflies, it undergoes incomplete metamorphosis with aquatic nymphal stages and short-lived winged adults. The species is part of the EPT (Ephemeroptera-Plecoptera-Trichoptera) biological index used to assess water quality.
Isonychia campestris
Isonychia campestris is a filter-feeding mayfly species described by McDunnough in 1931. The immature nymphs inhabit lotic aquatic systems where they employ specialized morphological structures to capture suspended particulate matter from the water column. This species has been studied specifically for its filter feeding mechanisms, which involve interception and diffusive deposition of particles smaller than the pore spaces between filtering structures. The species occurs in the Nearctic region of North America.
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 obscura
brushlegged mayfly
Isonychia obscura is a species of brushlegged mayfly in the family Isonychiidae. It is native to North America. Like other members of the genus Isonychia, it is an aquatic insect with a life cycle that includes nymphal stages in water and brief adult stages. Adults are known as "slate drakes" among anglers.
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.
Iswaeon anoka
small minnow mayfly
Iswaeon anoka is a species of small minnow mayfly in the family Baetidae, first described by Daggy in 1945. The species is currently recognized under the genus Iswaeon, though it has been treated as a synonym of Heterocloeon anoka in some taxonomic databases. Like other members of Baetidae, it belongs to the diverse group of small mayflies commonly found in freshwater habitats.
Labiobaetis
Labiobaetis is a genus of small mayflies in the family Baetidae, comprising over 150 described species distributed across tropical and temperate regions worldwide. The genus exhibits exceptional diversity in Southeast Asia, New Guinea, and Indonesia, with significant representation also in Africa, India, and western North America. Species identification relies primarily on larval morphology, particularly characters of the mouthparts, antennae, and gills. Adults are generally difficult to distinguish at the generic level.
Leptophlebia cupida
Early Brown Spinner, Black Quill
Leptophlebia cupida is a pronggilled mayfly species native to North America, commonly known as the early brown spinner or black quill. The species exhibits a univoltine life cycle with egg diapause during summer months. Nymphs develop through approximately 20-34 instars over 10 months, with emergence occurring from late April to mid-May. Adults are short-lived, non-feeding, and mate in swarms near streams.
Leptophlebia intermedia
Leptophlebia intermedia is a species of pronggilled mayfly in the family Leptophlebiidae. It was described by Traver in 1932. The species is found in North America.
Leptophlebia nebulosa
prong-gilled mayfly
Leptophlebia nebulosa is a species of prong-gilled mayfly in the family Leptophlebiidae. It is found in North America. The species belongs to a group characterized by their forked or prong-like gills, a distinctive morphological feature of the family Leptophlebiidae.
Leptophlebia pacifica
Leptophlebia pacifica is a species of pronggilled mayfly in the family Leptophlebiidae. It was described by McDunnough in 1933. The species occurs in North America within the Nearctic realm. As a member of Leptophlebiidae, it possesses the forked gills characteristic of this family.
Leucrocuta aphrodite
Leucrocuta aphrodite is a species of flatheaded mayfly in the family Heptageniidae. It inhabits freshwater streams and rivers in eastern North America. The species was described by McDunnough in 1926.
Leucrocuta hebe
flatheaded mayfly
Leucrocuta hebe is a species of flatheaded mayfly in the family Heptageniidae. This species is found across parts of North America, including the northern and southeastern United States and northern Canada. As a member of the order Ephemeroptera, it has an aquatic larval stage and a short-lived adult stage.
Leucrocuta juno
Leucrocuta juno is a species of flatheaded mayfly in the family Heptageniidae, described by McDunnough in 1924. It belongs to the order Ephemeroptera, a group of aquatic insects known for their brief adult lifespan. The species is native to North America and is part of a genus characterized by distinctive morphological features typical of heptageniid mayflies.
Leucrocuta minerva
Leucrocuta minerva is a species of mayfly in the family Heptageniidae, described by McDunnough in 1924. It belongs to a genus of small to medium-sized flat-headed mayflies commonly known as "little yellow quills" or similar vernacular names. Species in this genus are typically associated with running water habitats. The specific epithet "minerva" refers to the Roman goddess of wisdom, though the etymological reasoning behind this choice is not documented in available sources.
Leucrocuta thetis
Leucrocuta thetis is a species of flatheaded mayfly in the family Heptageniidae. It is known from North America. As a member of the Heptageniidae, it belongs to a group of mayflies commonly associated with running water habitats. The species was described by Traver in 1935.
Maccaffertium
flatheaded mayflies
Maccaffertium is a genus of mayflies in the family Heptageniidae, commonly known as flatheaded mayflies. The genus was established by Bednarik in 1979 and contains approximately 19–20 described species. Like other members of Heptageniidae, these mayflies are characterized by their flattened, streamlined bodies adapted for life in flowing water. The genus is found in North America, with species distributed across various freshwater habitats.
Maccaffertium exiguum
flatheaded mayfly
Maccaffertium exiguum is a species of flatheaded mayfly in the family Heptageniidae. This aquatic insect is native to North America, with a documented range extending across southeastern Canada and the eastern United States. Like other members of the genus, it develops through aquatic nymphal stages in freshwater habitats before emerging as a winged adult.
Maccaffertium luteum
Maccaffertium luteum is a species of flat-headed mayfly in the family Heptageniidae, originally described by Clemens in 1913. The genus Maccaffertium was historically treated as a subgenus of Stenonema but was elevated to full generic status based on morphological and phylogenetic studies. Like other members of its family, this species exhibits the characteristic subimago stage—a sexually immature winged form unique to mayflies that requires one final molt to reach reproductive adulthood.
Maccaffertium mediopunctatum
flat-headed mayfly
Maccaffertium mediopunctatum is a species of flat-headed mayfly in the family Heptageniidae. It occurs in Southeastern Canada and the Eastern United States. The species has two recognized subspecies: M. m. arwini and M. m. mediopunctatum. Like other members of its genus, it exhibits the unique mayfly developmental trait of having a fully winged subadult stage (subimago) that requires one additional molt to reach sexual maturity.
Maccaffertium mediopunctatum arwini
A subspecies of mayfly in the family Heptageniidae. Like other members of its genus, it exhibits the characteristic subimago stage—fully winged but sexually immature—unique among insects. Adults are short-lived, emerging from aquatic habitats to mate. The subspecific epithet honors an individual, following the pattern of other Maccaffertium subspecies.
Maccaffertium mediopunctatum mediopunctatum
Maccaffertium mediopunctatum mediopunctatum is a subspecies of mayfly in the family Heptageniidae. The genus Maccaffertium was established to accommodate species formerly placed in Heptagenia and related genera, distinguished by particular features of the male genitalia and wing venation. This subspecies is part of a group of flatheaded mayflies commonly found in North American streams and rivers. Subimagos (subadults) of this species exhibit the characteristic pale, milky-white coloration and opaque wings typical of the genus, with sexual dimorphism in eye size and abdominal claspers.
Maccaffertium meririvulanum
fresh flat-headed mayfly
Maccaffertium meririvulanum is a species of flatheaded mayfly in the family Heptageniidae, characterized by its distinctive flattened head morphology typical of this group. The species is known from North America, where it inhabits freshwater lotic environments. As with other members of the genus, it undergoes the unique mayfly developmental pattern involving a winged subadult (subimago) stage that molts once more to reach sexual maturity.
Maccaffertium mexicanum
flatheaded mayfly
A flatheaded mayfly species in the family Heptageniidae. Adults are attracted to light sources near aquatic habitats. The species possesses the unique mayfly trait of developing fully functional wings during the subimago (sub-adult) stage, requiring one additional molt to reach sexual maturity. Two subspecies are recognized: M. m. integrum and M. m. mexicanum.
Maccaffertium mexicanum integrum
Maccaffertium mexicanum integrum is a subspecies of mayfly in the family Heptageniidae. Like other members of its order, it undergoes a unique developmental process involving a winged subadult stage (subimago) that molts once more before reaching sexual maturity. The subspecies has been documented in the Nearctic and Neotropical regions, with observations from the Mississippi River lowlands of southeastern Missouri.
Maccaffertium modestum
flatheaded mayfly
Maccaffertium modestum is a species of flatheaded mayfly in the family Heptageniidae. It occurs in North America, specifically in the eastern United States and southeastern Canada. The species exhibits the characteristic subimago stage typical of mayflies, where fully functional wings develop before the final molt to adulthood.
Maccaffertium pudicum
flatheaded mayfly
Maccaffertium pudicum is a species of flatheaded mayfly in the family Heptageniidae. It is found in North America. The species exhibits the characteristic subimago stage typical of mayflies, where fully functional wings develop before the final molt to adulthood.
Maccaffertium smithae
Maccaffertium smithae is a species of flatheaded mayfly in the family Heptageniidae, described by Traver in 1937. As a member of the Heptageniidae family, it possesses the characteristic flattened head shape typical of this group. The species is known from North America, though specific details about its biology and ecology remain limited in the available literature.
Maccaffertium terminatum
flatheaded mayfly
Maccaffertium terminatum is a species of flatheaded mayfly in the family Heptageniidae. It is widely distributed across Canada and the Nearctic region. The species possesses the characteristic subimago stage typical of mayflies, where sexually immature adults with opaque, milky-white wings emerge from water before undergoing a final molt to the reproductive adult stage. Two subspecies are recognized: M. t. terminatum and M. t. placitum.
Maccaffertium terminatum placitum
Maccaffertium terminatum placitum is a subspecies of mayfly in the family Heptageniidae. Like other members of the genus, it exhibits the unique mayfly developmental trait of having a functional winged sub-adult stage (subimago) prior to the final molt to sexual maturity. The subimago is characterized by milky-white, opaque wings and paler body coloration compared to the transparent-winged adult. This subspecies is part of the Nearctic fauna of North America.
Matriella teresa
Matriella teresa is a species of spiny crawler mayfly in the family Ephemerellidae, described by Traver in 1934. It belongs to a genus of mayflies found in North America. As with other members of Ephemerellidae, it likely inhabits freshwater streams and rivers during its aquatic nymphal stage.
Metretopus borealis
Metretopus borealis is a mayfly species in the family Metretopodidae, originally described as Heptagenia borealis by Eaton in 1871. It is distributed across the Nearctic and Palearctic regions, with confirmed presence in North America. The species belongs to a small family of mayflies whose members are typically associated with cool, flowing waters.
Neocloeon
Neocloeon is a genus of mayflies in the family Baetidae. The species Neocloeon triangulifer has emerged as an important laboratory model organism for aquatic ecotoxicology and physiological studies due to its sensitivity to environmental stressors and ability to complete its life cycle in controlled conditions. The genus is distinguished by parthenogenetic reproduction in at least some populations, a trait that facilitates laboratory culture. Species in this genus inhabit freshwater streams and serve as bioindicators for water quality assessment.
Neoephemera purpurea
large squaregill mayfly
Neoephemera purpurea is a species of large squaregill mayfly in the family Neoephemeridae. It was originally described as Oreianthus purpureus by Traver in 1931. The species is known from North America, though specific details about its biology and ecology remain poorly documented.
Neoephemera youngi
Neoephemera youngi is a species of mayfly in the family Neoephemeridae, described by Berner in 1953. It belongs to a small family of mayflies with limited distribution records in the Nearctic region. Very little specific information about this species' biology, ecology, or appearance has been documented in accessible literature.
Neoleptophlebia assimilis
Southeastern Prong-gilled Mayfly
Neoleptophlebia assimilis is a species of prong-gilled mayfly in the family Leptophlebiidae. It is known from the southeastern United States. The species belongs to a genus characterized by gills with divided, finger-like lobes. Mayflies in this family are typically associated with running water habitats and serve as important indicators of water quality.
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.
Neoleptophlebia mollis
soft prong-gilled mayfly
Neoleptophlebia mollis is a species of prong-gilled mayfly in the family Leptophlebiidae. The species was first described by Eaton in 1871. It belongs to a genus characterized by forked gills on abdominal segments, a trait reflected in the common name "prong-gilled mayfly." The specific epithet "mollis" (Latin for "soft") likely refers to some aspect of the species' morphology or texture.
Nixe
Nixe is a genus of mayflies in the family Heptageniidae, established by Flowers in 1980. These aquatic insects belong to the order Ephemeroptera, characterized by their short adult lifespan and complex life cycles involving aquatic nymphal stages. The genus has been documented in 451 iNaturalist observations, indicating moderate levels of citizen science engagement. As heptageniid mayflies, members of this genus likely inhabit flowing water environments where their nymphs develop.
Nixe inconspicua
Nixe inconspicua is a species of flatheaded mayfly in the family Heptageniidae, first described by McDunnough in 1924. As a member of the Heptageniidae, it possesses the characteristic dorsoventrally flattened body form typical of this family. The species is known from North America, though specific details about its biology and ecology remain limited in the available literature.
Nixe lucidipennis
clear-winged flat-headed mayfly
Nixe lucidipennis is a species of flat-headed mayfly in the family Heptageniidae, distributed across North America. The species was described by Clemens in 1913. It is known from a limited number of observations, with records indicating presence in the Nearctic region. As a member of the genus Nixe, it belongs to a group of mayflies characterized by their flattened head morphology and association with running water habitats.
Pannota
Pannota is an infraorder of mayflies (Ephemeroptera) distinguished from its sister group Schistonota by the degree of wing pad fusion in final-stage nymphs: in Pannota, fusion along the mesothorax is less than half the fore-wing length, whereas in Schistonota it exceeds half. Nymphs are slow-moving crawlers with modified gill morphology, contrasting with the active swimmers, burrowers, and sprawlers of Schistonota. The group includes two superfamilies, Caenoidea and Ephemerelloidea, encompassing seven families. Members are important bioindicators of freshwater ecosystem health due to their sensitivity to pollution.
Paracloeodes minutus
small minnow mayfly
Paracloeodes minutus is a small minnow mayfly in the family Baetidae. It is found in Central America and North America, including southeastern Canada, northern Mexico, and the continental United States. The species was described by Daggy in 1945.