Ephemeroptera
Guides
Acentrella
small minnow mayflies
Acentrella is a genus of small minnow mayflies in the family Baetidae. The genus contains at least 26 species distributed across Europe, North America, Asia, and Africa. Nymphs of at least some species inhabit cool, clean, swift rocky streams. Adult stages of several species remain undescribed due to the difficulty of rearing nymphs to maturity.
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 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.
Ametropodidae
Ametropodidae is a family of mayflies in the order Ephemeroptera. The family contains at least three genera: Ametropus, Brevitibia, and Palaeometropus. Species within this family are primarily found in large river systems. The family is classified within the superfamily Baetoidea, which includes some of the most primitive living mayfly species.
Ametropus
sand minnows
Ametropus is a genus of mayflies (Ephemeroptera) commonly known as sand minnows, belonging to the family Ametropodidae. The genus contains at least three described species: A. ammophilus, A. fragilis, and A. neavei. Species in this genus are adapted to large river systems and exhibit specialized ecological traits including deep-water nymphal habitats and detritivorous feeding habits.
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 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
hacklegilled burrower mayflies
Anthopotamus is a genus of hacklegilled burrower mayflies in the family Potamanthidae, established by McCafferty & Bae in 1990. The genus contains at least four described species distributed in North America. Larvae are specialized burrowers in riverine substrates, notable for their fossorial lifestyle in the hyporheic zone using tusk-like structures for excavation. Adults are short-lived and primarily reproductive.
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.
Arthroplea bipunctata
flatheaded mayfly
Arthroplea bipunctata is a species of flatheaded mayfly in the family Heptageniidae (sometimes historically placed in Arthropleidae). It is known from North America, with records from the Nearctic region. The species was described by McDunnough in 1924, originally as Cinygma bipunctata. Like other flatheaded mayflies, it belongs to a group adapted to clinging in fast-flowing waters.
Arthropleidae
flatheaded mayflies
Arthropleidae is a family of mayflies in the order Ephemeroptera, characterized by flattened heads. The family contains at least two genera: the extant Arthroplea and the extinct Electrogenia. Members are aquatic insects with life cycles involving aquatic nymphal stages and short-lived winged adults.
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.
Baetidae
small mayflies, small minnow mayflies
Baetidae is the most species-diverse family of mayflies, comprising approximately 1,000 described species in 110-114 genera worldwide and representing about one-third of all mayfly diversity. Adults are among the smallest mayflies, rarely exceeding 10 mm in length excluding tails, with some species much smaller. The family has a cosmopolitan distribution except for New Zealand and occupies a relatively basal position in Ephemeroptera phylogeny.
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 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
squaregilled mayflies
Brachycercus is a genus of small mayflies in the family Caenidae, commonly known as squaregilled mayflies. The genus is characterized by its distinctive square-shaped gills and is distributed primarily in the Palaearctic and Nearctic realms. At least six species have been described, including B. harrisella, which is the type species described by Curtis in 1835.
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.
Caenoidea
Caenoidea is a superfamily of mayflies within the suborder Pannota, distinguished by the filamentous gills of their nymphs. It comprises four families: Baetiscidae, Caenidae, Neoephemeridae, and Prosopistomatidae. The filamentous gill structure serves as the primary diagnostic feature separating this group from the related superfamily Ephemerelloidea.
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 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 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.
Camelobaetidius
minnow mayflies
Camelobaetidius is a genus of small minnow mayflies in the family Baetidae, comprising at least 40 described species distributed across the Nearctic and Neotropical regions. The genus is one of the most studied within Baetidae, with nymphs commonly inhabiting lotic (flowing water) environments. Species are distinguished by specific morphological characters, particularly the spatulate (flattened, spoon-shaped) tarsal claws present in nymphs. The genus exhibits considerable diversity in Central and North America, with additional species described from Costa Rica and southeastern Brazil.
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.