Mayflies
Guides
Acanthametropodidae
Acanthametropodidae is a family of sand-dwelling mayflies (Ephemeroptera) in the suborder Pisciforma. The family contains at least two genera—Acanthametropus and Analetris—with four described species. These insects are specialized for life in sandy substrates, a relatively uncommon habitat among mayflies.
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.
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.
Analetris
Analetris is a genus of sand-dwelling mayflies in the family Acanthametropodidae, established by Edmunds in 1972. The genus contains at least two species: the extant Analetris eximia and the extinct †Analetris secundus. Members of this genus are specialized inhabitants of riverine environments with unstable silty substrates. The best-studied species, A. eximia, is considered endangered due to habitat destruction from reservoir construction.
Baetiscidae
armored mayflies
Baetiscidae is a family of mayflies distinguished by their heavily armored nymphs bearing a robust, spiked thoracic notal shield that extends over part of the abdomen. The family contains a single extant genus, Baetisca, with approximately 12 species endemic to North America. Three extinct genera (Protobaetisca, Balticobaetisca, Koonwarrabaetisca) are known from Cretaceous and Eocene deposits, indicating a Pangean origin for the family by at least the Early Jurassic. Together with Prosopistomatidae, Baetiscidae forms the clade Carapacea, characterized by specialized larval armor.
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.
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.
Carapacea
Carapacea is a suborder of mayflies (Ephemeroptera) characterized by nymphs possessing a distinctive carapace-like structure formed from expanded and fused thoracic tergites. This morphological adaptation distinguishes them from other mayfly suborders. The group includes families such as Baetiscidae and Prosopistomatidae. Carapacean mayflies are primarily found in running water habitats.
Cinygmula
Cinygmula is a genus of flatheaded mayflies (Heptageniidae) comprising at least 30 described species. The genus is characterized by distinctive morphological features in some species, including pointed claws and a distinct frontal fold on the imago. Species occur in high-altitude alpine habitats across central Asia and the eastern Himalaya. The genus has been studied for its potential use as a bioindicator of aquatic contamination.
Cloeon
Double-gilled Pond Creepers
Cloeon is a cosmopolitan genus of mayflies in the family Baetidae, commonly known as Double-gilled Pond Creepers. Species in this genus are aquatic as larvae (naiads) and inhabit diverse freshwater environments. At least one species, C. dipterum, is known to give birth to live naiads rather than laying eggs externally. The genus has been studied for its tolerance to environmental stressors including temperature and oxygen fluctuations.
Drunella
Blue-winged Olives, Spiny Crawler Mayflies
Drunella is a genus of spiny crawler mayflies in the family Ephemerellidae, comprising at least 20 described species. These mayflies are aquatic insects with nymphs that inhabit stream environments and are significant components of freshwater food webs. Adults are important to fly fishermen, who commonly refer to them as "Blue-winged Olives" and imitate them with artificial flies. Some species, such as Drunella grandis (the green drake), are particularly valued as trout food sources.
Ecdyonurus
Ecdyonurus is a genus of mayflies in the family Heptageniidae, comprising approximately 66 described species distributed primarily across Europe and parts of North Africa and Asia. The genus is taxonomically well-studied, with multiple species described in recent decades from mountain regions including the Carpathians, Crimean Peninsula, and Aurès Mountains. Species within this genus are typically associated with running waters and have been subjects of ecological studies on larval growth and thermal biology.
Ephemeridae
Burrowing Mayflies
Ephemeridae is a family of large mayflies comprising approximately 150 described species distributed worldwide except Australia and Oceania. Adults range up to 35 mm in length and possess either two or three elongated caudal filaments. Many species exhibit distinctively patterned wings. The family is commonly known as "burrowing mayflies" due to the fossorial adaptations of their nymphs, which inhabit silty or sandy substrates in freshwater systems. Nymphs possess specialized morphological features including spur-like projections on foretibiae, dorsally positioned plumose and lanceolate abdominal gills, and mandibular tusks that facilitate burrowing behavior.
Habrophlebiodes
Habrophlebiodes is a genus of mayflies in the family Leptophlebiidae, established by Ulmer in 1920. The genus contains species distributed across Asia and the Americas, with at least four Asian species documented. Asian species include three endemics to China (H. gilliesi, H. tenella, H. zijinensis) plus H. prominens. The genus is divided into two distinct clades with morphological differences separating Asian and American species.
Heptageniidae
Stream Mayflies, Flat-headed Mayflies
Heptageniidae is a family of mayflies comprising over 500 described species, commonly known as stream mayflies or flat-headed mayflies. Members are generally small with three long tails, clear wings with prominent venation, and males possess large compound eyes that are not divided into upper and lower parts. The family is primarily distributed across the Holarctic, Oriental, and Afrotropical regions, with additional presence in Central American tropics and extreme northern South America. Nymphs are flattened in shape, typically dark in coloration, and inhabit fast-flowing streams where they exhibit diverse feeding strategies including herbivory, scavenging, and predation.
Heptagenioidea
Heptagenioidea is a superfamily of mayflies (Ephemeroptera) distributed across most global regions except the Arctic and Antarctic. The superfamily likely originated in the Jurassic period, coinciding with a shift from still-water to flowing-water breeding habitats. This ecological transition drove rapid radiation and morphological adaptations, including modifications to mouthparts and forelegs for passive feeding in current. Heptageniidae represents the most widely distributed family within this group.
Heterocloeon
small minnow mayflies
Heterocloeon is a genus of small minnow mayflies in the family Baetidae, containing approximately nine described species. These mayflies are part of the diverse Baetidae family, which is one of the largest families of mayflies. The genus was established by McDunnough in 1925. Species within this genus have been studied in relation to environmental modifications, particularly the effects of reservoir impoundment on their life history.
Homoeoneuria
brushleg mayflies
Homoeoneuria is a genus of brushleg mayflies in the family Oligoneuriidae, established by Eaton in 1881. The genus contains at least five described species, with confirmed records in North America (including the type species H. salviniae) and South America (Brazil, Peru, Argentina, and Colombia). A new species, H. (H.) watu, was described from Southeastern Brazil based on distinctive adult and nymphal morphological characters. The genus is poorly documented in northern South America, with recent confirmations extending its known range.
Isonychiidae
Brush-legged Mayflies
Isonychiidae is a monogeneric family of mayflies containing the single extant genus Isonychia Eaton, 1871, with approximately 37 species distributed across the Holarctic and Oriental regions. The family is characterized by distinctive brush-like or hairy legs in the adult stage, giving rise to the common name "brush-legged mayflies." Species inhabit flowing water habitats, with nymphs occurring on rocky substrates in streams and creeks. The family is among the earliest reported groups of Chinese Ephemeroptera and is relatively abundant at suitable sampling sites.
Leptohyphes
little stout crawler mayflies
Leptohyphes is a genus of small, robust mayflies in the family Leptohyphidae, commonly referred to as "little stout crawler mayflies." The genus contains approximately 18 described species distributed primarily in the Neotropics, with a concentration in South America. Species in this genus are characterized by their crawling behavior and compact body form. The genus was established by Eaton in 1882.
Macdunnoa
Macdunnoa is a genus of mayflies in the family Heptageniidae, established by Lehmkuhl in 1979. The genus belongs to the order Ephemeroptera, a group of aquatic insects known for their brief adult lifespan. Very few observations of this genus have been recorded, with only a single documented observation in iNaturalist. As a member of Heptageniidae, it is part of a diverse family of flat-headed mayflies commonly found in running water habitats.
Matriella
Matriella is a genus of mayflies in the family Ephemerellidae, established by Jacobus & McCafferty in 2008. As a relatively recently described genus within the spiny crawler mayfly family, it represents part of the ongoing taxonomic refinement of Ephemerellidae. The genus belongs to the order Ephemeroptera, an ancient group of aquatic insects with aquatic immature stages and terrestrial adults. Specific details about species diversity and biology within Matriella remain limited in available sources.
Metretopodidae
cleftfooted minnow mayflies
Metretopodidae is a family of mayflies in the order Ephemeroptera, commonly known as cleftfooted minnow mayflies. The family contains at least 3 genera (Metreplecton, Metretopus, Siphloplecton) and more than 20 described species. These mayflies are part of the diverse aquatic insect fauna associated with freshwater habitats.
Metretopus
Metretopus is a genus of mayflies (Ephemeroptera) in the family Metretopodidae, containing at least two species: M. alter and M. borealis. These insects are found across northern regions of Europe, Russia, and North America. The genus has historically posed identification challenges, with M. alter frequently misidentified as M. borealis until morphological distinguishing characters were established.
Neoephemera
large squaregill mayflies
Neoephemera is a genus of large squaregill mayflies in the family Neoephemeridae, established by McDunnough in 1925. The genus contains approximately six extant species distributed across North America and Asia, plus one extinct species from the Eocene of Washington State. Species range from moderate to large size within the family, with body lengths varying considerably. The genus has been subject to taxonomic revision, with at least one species (N. projecta) transferred to a new genus Pulchephemera based on phylogenetic analysis of plesiomorphic characters.
Neoephemeridae
large squaregill mayflies
Neoephemeridae is a small family of mayflies in the suborder Furcatergalia, containing approximately 13-17 described species across four genera: Neoephemera (Nearctic), Ochernova (Central Asia), Leucorhoenanthus (West Palearctic), and Potamanthellus (East Palearctic and Oriental). Nymphs are characterized by distinctive fimbriate (fringed) dorsal-oriented gills on abdominal segments, giving rise to the common name "large squaregill mayflies." The family has a disjunct Holarctic-Oriental distribution with recent findings in southwestern and northwestern China linking previously isolated genera biogeographically.
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.
Palingeniidae
spiny-headed burrowing mayflies
Palingeniidae is a family of large mayflies commonly known as spiny-headed burrowing mayflies. Adults are characterized by having more than four longitudinal cross-veins on their wings, with males possessing short, wide pronota and well-developed legs in both sexes. Female cerci are shorter than the body. Nymphs are burrowers in muddy substrates of large rivers. The family includes notable species such as Palingenia longicauda, the largest European mayfly at up to 12 cm in length.
Paracloeodes
Paracloeodes is a genus of small minnow mayflies in the family Baetidae, established by Day in 1955. The genus contains at least 23 described species distributed across the Americas, with the highest diversity concentrated in the Neotropical region. Nymph-adult associations have been established for only nine species, indicating significant gaps in life stage knowledge. Recent taxonomic work has focused on describing new species and clarifying previously unknown adult stages, such as for P. carolinae.
Penelomax
Penelomax is a genus of spiny crawler mayflies in the family Ephemerellidae, established by Jacobus and McCafferty in 2008. The genus contains a single described species, Penelomax septentrionalis. These mayflies belong to the order Ephemeroptera, a group characterized by short adult lifespans and aquatic larval stages.
Plauditus
small minnow mayflies
Plauditus is a genus of small minnow mayflies in the family Baetidae, established by Lugo-Ortiz & McCafferty in 1998. The genus contains approximately 10 described species distributed in North America. These mayflies are aquatic insects with larvae that exhibit considerable morphological and color variation, particularly in abdominal patterning.
Siphlonuridae
primitive minnow mayfly
Siphlonuridae, commonly called primitive minnow mayflies, is a family of mayflies (Ephemeroptera) characterized by morphological traits considered ancestral within the order. Members are adapted to cool waters and occur across temperate regions of the Northern Hemisphere. The family includes approximately six extant genera: Ameletoides, Edmundsius, Parameletus, Siphlonisca, Siphlonurus, and the former genus Metretopus (now sometimes placed in Siphlonuridae). Nymphs inhabit diverse freshwater habitats including temporary ponds, streams, and floodplains, with habitat preferences often shifting during ontogeny.
Traverella
Traverella is a genus of pronggilled mayflies established by Edmunds in 1948. It belongs to the family Leptophlebiidae, one of the most diverse families within the order Ephemeroptera. The genus comprises 13 described species. Members of this genus, like other leptophlebiid mayflies, possess the characteristic forked gills on their abdominal segments that give the family its common name.
Tricorythodes
little stout crawler mayflies
Tricorythodes is a genus of small, robust mayflies in the family Leptohyphidae, commonly known as little stout crawler mayflies. The genus comprises approximately 16 described species distributed across the Americas. Nymphs are primarily found in stream habitats where they function as collector-gatherers, processing fine particulate organic matter. Species within this genus exhibit multivoltine life histories with development rates strongly influenced by temperature.