Mayfly
Guides
Acentrella feropagus
Acentrella feropagus is a small mayfly species in the family Baetidae, described in 2000 from North American material. It belongs to a genus of minute, delicate mayflies commonly known as small minnow mayflies. The species is known from limited collection records in the Nearctic region.
Acentrella insignificans
Acentrella insignificans is a species of small minnow mayfly in the family Baetidae. It was originally described as Baetis insignificans by McDunnough in 1926. The species has a broad distribution across North America and Central America, with records extending from Alaska and northern Canada through the southwestern United States and into Mexico.
Acentrella nadineae
small minnow mayfly
Acentrella nadineae is a small minnow mayfly in the family Baetidae. The species was described in 2009 and remained known only from nymphs until successful rearing produced the first documented adults. It inhabits cool, clean, swift rocky streams across parts of the eastern and midwestern United States. Near final instar nymphs exhibit unusual madicolous behavior, living in thin water films on rock surfaces.
Acentrella turbida
Acentrella turbida is a small minnow mayfly in the family Baetidae, first described by McDunnough in 1924. It is one of the most widespread mayfly species in North America, occurring across the continent from Alaska and Canada through the continental United States to northern Mexico, with additional populations in Central America. The species was originally described under the genus Pseudocloeon before being transferred to Acentrella. It belongs to a diverse genus containing numerous small, delicate mayfly species often difficult to distinguish without close examination.
Acerpenna macdunnoughi
small minnow mayfly
Acerpenna macdunnoughi is a species of small minnow mayfly in the family Baetidae. Originally described as Baetis macdunnoughi by Ide in 1937, it was later transferred to the genus Acerpenna. The species is found in North America.
Ameletidae
combmouthed minnow mayflies
Ameletidae is a family of mayflies commonly known as combmouthed minnow mayflies. The family includes the speciose genus Ameletus, which reaches its greatest diversity in southwestern North America with up to 12 species co-occurring at single sites. The genus Metreletus has a trans-Palaearctic distribution with three recognized species. Ameletidae larvae are aquatic and occur in lotic habitats from small headwater streams to larger rivers.
Ameletus
Upland Summer Mayfly (A. inopinatus)
Ameletus is a genus of mayflies (Ephemeroptera) and the type genus of the family Ameletidae, circumscribed by Rev. A. E. Eaton in 1885. The genus is speciose, with approximately 30 bisexual species recognized in North America and additional species in Europe and Asia. Ameletus species occur in cold-water streams from small headwater brooks to larger rivers, with greatest diversity in mountainous regions of western North America. The genus includes A. inopinatus, the only predominantly montane mayfly species in the UK and a noted climate change indicator species.
Ameletus browni
purple marram
Ameletus browni is a mayfly species in the family Ameletidae, commonly known as the "purple marram." It was described by McDunnough in 1933 based on nymphal specimens collected in southern British Columbia. The species belongs to the Nearctic fauna and is found in northeastern North America, including Canada and the northeastern United States. Like other members of the genus Ameletus, it is associated with cool, clean freshwater habitats.
Ameletus celer
Ameletus celer is a Nearctic species of mayfly in the family Ameletidae, described by McDunnough in 1934. As a member of the genus Ameletus, it belongs to a group of mayflies commonly known as the "prong-gilled mayflies" due to the distinctive forked structure of their gills. The species occurs in North America, though specific ecological details remain poorly documented in the available literature.
Ameletus ludens
Ameletus ludens is a species of combmouthed minnow mayfly in the family Ameletidae, described by Needham in 1905. It belongs to the order Ephemeroptera, a group of aquatic insects known for their brief adult lifespans. The species is found in North America, though specific details about its ecology and life history remain limited in available sources.
Ameletus similior
Ameletus similior is a mayfly species (Ephemeroptera: Ameletidae) described by McDunnough in 1928. It occurs in western North America from southern British Columbia to Alberta, with identification keys also applicable to Saskatchewan, Montana, and northern Idaho and Washington. The species was previously known as A. monta, which has been synonymized with A. similior. Adult males have practically clear hyaline wings and differ from the similar A. alticolus in genitalic characters.
Ameletus subnotatus
combmouthed minnow mayfly
Ameletus subnotatus is a species of combmouthed minnow mayfly in the family Ameletidae. It is one of 13 bisexual Ameletus species documented in Alberta, Canada, where it occurs across virtually all hydrographic basins from small headwater streams to large rivers. The species is found throughout Canada and extends into the northern and southwestern United States.
Ameletus validus
combmouthed minnow mayfly
Ameletus validus is a species of mayfly in the family Ameletidae, first described by McDunnough in 1923. It is one of approximately 30 bisexual species recognized in the genus Ameletus across North America. The species occurs in running waters from small headwater streams to large rivers, with documented populations in western North America including Alberta, British Columbia, and the western United States. Taxonomic work has clarified that adult wings are lightly and evenly suffused with brownish-amber, not speckled as previously miskeyed.
Ameletus velox
Ameletus velox is a North American mayfly species described by Dodds in 1923. It belongs to the family Ameletidae, a group of predatory mayflies known for their distinctive larval morphology and behavior. The species is part of the Nearctic fauna with documented presence in North America. As with other Ameletus species, it likely inhabits cool freshwater streams, though specific ecological details for this species remain limited in available literature.
Ameletus vernalis
combmouthed minnow mayfly
Ameletus vernalis is a species of combmouthed minnow mayfly in the family Ameletidae. It is found in southwestern Canada and the western United States, particularly in western Alberta where it occurs across diverse watersheds from small headwater streams to large rivers. The species was described by McDunnough in 1924, and its nymphs were associated with adults through field work in southern British Columbia in 1935.
Ametropus ammophilus
sand minnow
Ametropus ammophilus is a species of mayfly in the family Ametropodidae, commonly known as the sand minnow. It was described by Allen and Edmunds in 1976. The species is known from a restricted geographic range in western North America.
Anafroptilum
Anafroptilum is a genus of small mayflies in the family Baetidae. The genus was first described from the East Palaearctic and Nearctic regions, with a single species A. kazlauskasi known from the former and eight species from the latter. In 2016, two new species were described from Thailand, marking the first report of the genus from the Oriental Region. Species in this genus are characterized by the absence of hind wings in adults and distinctive larval morphological features.
Anafroptilum bifurcatum
Anafroptilum bifurcatum is a species of small mayfly in the family Baetidae, first described by McDunnough in 1924. The genus Anafroptilum was established to accommodate certain Baetidae species previously placed in other genera, distinguished by specific morphological features of the genitalia and wing venation. As a member of the Baetidae, it belongs to a diverse family of small, agile mayflies commonly known as blue-winged olives or small minnow mayflies.
Anafroptilum conturbatum
Anafroptilum conturbatum is a species of small mayfly in the family Baetidae. As a member of this diverse family, it inhabits freshwater environments where it contributes to aquatic food webs. The species was described by McCafferty and Waltz in 1995. Like other baetid mayflies, it likely has a short adult lifespan focused primarily on reproduction.
Anafroptilum minor
Anafroptilum minor is a species of small minnow mayfly in the family Baetidae. Like other members of this family, it is characterized by reduced wing venation and relatively simple morphology compared to other mayfly families. The genus Anafroptilum contains species that are typically associated with running water habitats. Specific ecological details for A. minor are limited in available literature.
Anthopotamus distinctus
Golden Drake, hacklegilled burrower mayfly
Anthopotamus distinctus is a species of mayfly in the family Potamanthidae, commonly known as the Golden Drake. It belongs to a group referred to as hacklegilled burrower mayflies, indicating specialized gill structures and burrowing behavior in the nymphal stage. The species is found in the Nearctic region of eastern North America.
Anthopotamus myops
hacklegilled burrower mayfly
Anthopotamus myops is a species of hacklegilled burrower mayfly in the family Potamanthidae. It inhabits freshwater environments in southeastern Canada and the eastern United States. As a member of the order Ephemeroptera, it has a short adult lifespan and aquatic nymphal stages.
Anthopotamus verticis
Walker's Tusked Sprawler
Anthopotamus verticis, commonly known as Walker's Tusked Sprawler, is a hacklegilled burrower mayfly in the family Potamanthidae. The species is found in southeastern Canada and parts of the northern and southeastern United States. As a member of the Potamanthidae, it belongs to a family of mayflies characterized by burrowing habits and distinctive gill structures.
Attenella margarita
spiny crawler mayfly
Attenella margarita is a species of spiny crawler mayfly in the family Ephemerellidae. It exhibits a disjunct east-west distribution pattern across North America, which is rare among mayflies. The species has been documented from the southern half of Canada and the continental United States, with a southeastern range extension to North Carolina representing approximately 1,300 km beyond previously known western localities.
Attenella soquele
Attenella soquele is a species of spiny crawler mayfly in the family Ephemerellidae. The species was described by Day in 1954 and is recognized as valid in current taxonomic databases. Members of the genus Attenella are characterized by their distinctive spiny abdominal tubercles and are primarily distributed in North America.
Baetis alius
small minnow mayfly
Baetis alius is a species of small minnow mayfly in the family Baetidae. It is found in the northwestern United States. As a member of the Baetis genus, it belongs to a diverse group of mayflies commonly known as blue-winged olives, though specific common names for this species are not well established.
Baetis bicaudatus
small minnow mayfly
Baetis bicaudatus is a small minnow mayfly in the family Baetidae, described by Dodds in 1923. It inhabits streams across western North America from Alaska to the southwestern United States and northern Canada. The species is bivoltine, producing two generations annually, with distinct summer and winter generations that differ in size and susceptibility to parasitism. Adults exhibit characteristic mayfly behavior including swarming mating aggregations, while nymphs are important grazers on periphyton in stream ecosystems.
Baetis brunneicolor
Blue-winged Rusty Dun
Baetis brunneicolor is a small minnow mayfly species in the family Baetidae, described by McDunnough in 1925. It occurs across northern North America, with records from all of Canada and portions of the United States. As a member of the genus Baetis, it belongs to a diverse group of small, agile mayflies commonly known as blue-winged olives or small minnow mayflies.
Baetis notos
Baetis notos is a species of small minnow mayfly in the family Baetidae. It is found in Central America and North America, with its North American range extending across southern Mexico, the southern United States, and the northwestern United States. The species was described by Allen and Murvosh in 1987.
Baetis piscatoris
Baetis piscatoris is a species of mayfly in the family Baetidae, first described by Jay Traver in 1935. The species is known from the Nearctic region, with records from North America. As a member of the genus Baetis, it belongs to a diverse group of small to medium-sized mayflies commonly referred to as 'blue-winged olives' in angling contexts.
Baetisca berneri
Baetisca berneri is an armored mayfly species described from West Virginia streams. The species has been the subject of ecological life history research examining nymphal development and emergence patterns. It belongs to a genus characterized by distinctive armored nymphal forms adapted to lotic environments.
Baetisca lacustris
Baetisca lacustris is a species of armored mayfly in the family Baetiscidae. It was described by James Halliday McDunnough in 1932. The species is found in North America and belongs to a genus characterized by distinctive armored body plates.
Baetisca rogersi
Baetisca rogersi is a mayfly species in the family Baetiscidae, endemic to northwestern Florida. The species has been the subject of detailed life history and ecological research documenting its external morphology, developmental stages, seasonal distribution, and emergence patterns. Its ecology is influenced by specific environmental factors affecting growth and development.
Behningiidae
Sand-burrowing Mayflies, Tuskless Burrowing Mayflies
Behningiidae is a small, primitive family of burrowing mayflies with four described genera: three extant (Behningia, Dolania, Protobehningia) and one fossil (†Archaeobehningia). Nymphs inhabit sandy river sediments but lack the tusk-like mandibular projections typical of other burrowing mayfly families. The family has a Holarctic distribution, with Dolania occurring in North America and the remaining genera in northern Europe and Asia. Members are rarely collected due to their subterranean lifestyle.
Brachycercus nitidus
Brachycercus nitidus is a species of small squaregill mayfly in the family Caenidae, first described by Traver in 1932. The genus Brachycercus is part of the superfamily Caenoidea, a group characterized by reduced wing venation and other adaptations to lentic (still-water) habitats. As a member of the Caenidae, this species likely exhibits the family's typical traits including small body size, short antennae, and forewings with few crossveins. The specific epithet "nitidus" (Latin for "shiny" or "polished") may refer to a characteristic sheen of the cuticle, though this interpretation is speculative without direct examination of type material.
Caenis
Common Square-gills
Caenis is a genus of small mayflies in the family Caenidae, commonly known as "square-gilled mayflies." Adults are among the smallest mayflies, with some species measuring only 3–4 mm in body length. The genus is globally distributed across multiple continents and serves as an indicator taxon for aquatic ecosystem health. Nymphs inhabit various freshwater environments, and adults emerge in synchronized events.
Caenis hilaris
Caenis hilaris is a species of small square-gilled mayfly in the family Caenidae. It is found in North America. As a member of the order Ephemeroptera, it shares the characteristic life history of mayflies, with aquatic nymphal stages and short-lived winged adults.
Callibaetis
Speckled Duns
Callibaetis is a genus of small minnow mayflies in the family Baetidae, comprising at least 30 described species distributed across North and South America. The genus has been taxonomically problematic, with recent phylogenetic work confirming its monophyly and establishing four subgenera. Species occupy diverse lentic habitats including ponds, lakes, and wetlands, with some populations adapted to variable salinity conditions.
Callibaetis californicus
small minnow mayfly
Callibaetis californicus is a small minnow mayfly in the family Baetidae, first described by Banks in 1900. The species occurs across Central America and western North America, including all of Mexico and the western United States. As a member of the Baetidae, it belongs to one of the most diverse families of mayflies, commonly known as small minnow mayflies for their streamlined, fish-like nymphal form.
Callibaetis ferrugineus
Red Speckled Dun
Callibaetis ferrugineus is a small minnow mayfly in the family Baetidae, commonly known as the Red Speckled Dun. The species is distributed across northern and southwestern Canada, the western United States, and Alaska. As with all mayflies, it undergoes incomplete metamorphosis with aquatic nymphal stages and short-lived adult stages. The species includes two recognized subspecies: C. f. ferrugineus and C. f. hageni.
Callibaetis ferrugineus ferrugineus
Callibaetis ferrugineus ferrugineus is a subspecies of small minnow mayfly in the family Baetidae. As a member of the genus Callibaetis, it belongs to a group of mayflies commonly known as pond mayflies or speckled mayflies. The subspecies is distributed in the Nearctic region, with records from North America including Vermont in the United States. Like other Baetidae, it has a relatively short adult lifespan focused on reproduction.
Callibaetis ferrugineus hageni
Callibaetis ferrugineus hageni is a subspecies of mayfly in the family Baetidae. The genus Callibaetis comprises small minnow mayflies found in aquatic habitats across North America. As with other mayflies in this genus, this subspecies has a multi-stage life cycle involving aquatic nymphs and short-lived winged adults. The subspecific epithet honors Hermann Hagen, a prominent 19th-century entomologist.
Callibaetis floridanus
small minnow mayfly
Callibaetis floridanus is a small minnow mayfly (Ephemeroptera: Baetidae) native to North and Central America. The species inhabits diverse aquatic environments including coastal ponds subject to saltwater intrusion and temporary wetlands (playas) in arid regions. Research demonstrates significant physiological plasticity in ion regulation, with populations capable of acclimating to salinities ranging from 113 to 9,921 µS/cm. Naiad development averages approximately 24 days from egg hatch to adulthood.
Callibaetis pallidus
small minnow mayfly
Callibaetis pallidus is a species of small minnow mayfly in the family Baetidae, first described by Banks in 1900. Like other members of the genus Callibaetis, it belongs to a group of mayflies commonly referred to as "small minnow mayflies" due to their streamlined bodies and swimming nymphal behavior. The species is documented from North America, though specific details about its ecology and distribution within this range remain limited in available literature.
Callibaetis pictus
Speckled Dun
Callibaetis pictus is a small minnow mayfly in the family Baetidae, commonly known as the Speckled Dun. It is distributed across Central America and North America, including all of Mexico and the northern and southwestern United States. Like other mayflies, it has an aquatic nymphal stage lasting months to years, followed by a brief adult lifespan measured in hours to days. The species is part of the EPT index (Ephemeroptera, Plecoptera, Trichoptera) used to assess water quality in environmental monitoring.
Callibaetis pretiosus
small minnow mayfly
Callibaetis pretiosus is a small minnow mayfly in the family Baetidae. The species was described by Banks in 1914 and is native to North America. Larvae have been documented in wet-weather pools, with records from the southeastern United States and a northward range extension to Pennsylvania. As a member of Ephemeroptera, it undergoes aquatic nymphal development followed by a brief terrestrial adult stage.
Caudatella
Caudatella is a genus of mayflies in the family Ephemerellidae, established by Edmunds in 1959. Species within this genus are primarily distributed in western North America, with documented occurrences in Montana and other regions. The genus has been subject to taxonomic revision, particularly regarding species complexes such as C. heterocaudata and C. hystrix. Larval stages are aquatic and associated with stream habitats.
Caudatella heterocaudata
A species of spiny crawler mayfly in the family Ephemerellidae, originally described by McDunnough in 1929. The species has undergone taxonomic revision, with Caudatella circia previously treated as distinct but now recognized as a synonym. Larvae possess diagnostic morphological characters that allow separation from the related C. hystrix complex.
Choroterpes
Choroterpes is a genus of mayflies in the family Leptophlebiidae, distributed across the Americas, Europe (excluding the British Isles), Africa, and Asia. The genus contains multiple subgenera, including the nominate subgenus Choroterpes and Neochoroterpes (North America). Nymphs are typically found in streams and rivers, often associated with leaf litter. The genus has been subject to taxonomic revision, with some species reassigned to new genera such as Tikuna.
Cinygma dimicki
Cinygma dimicki is a species of flat-headed mayfly in the family Heptageniidae, described by James Halliday McDunnough in 1934. It belongs to a genus of North American mayflies characterized by distinctive head morphology adapted for clinging to substrates in flowing water. The species is known from the Nearctic region, though specific ecological details remain poorly documented in published literature.