Mass-emergence
Guides
Chauliodinae
Fishflies
Fishflies (subfamily Chauliodinae) are large, winged insects in the megalopteran family Corydalidae. Adults are distinguished from their close relatives, dobsonflies, by their relatively unremarkable mandibles and feathery antennae in males. Larvae are aquatic predators that inhabit clean, flowing streams, where they prey on other aquatic insects and small vertebrates. The subfamily contains approximately 15 genera and nearly 110 species distributed across North America, South America, Africa, Australia, and Asia.
Chironomidae
non-biting midges, chironomids, lake flies, bay flies, sand flies, muckleheads, muffleheads, Canadian soldiers, American soldiers, blind mosquitoes, chizzywinks, bloodworms (larval stage)
Chironomidae is a large family of non-biting midges with over 10,000 described species globally. Adults are frequently mistaken for mosquitoes due to their similar body shape, but they lack wing scales and piercing mouthparts. The family exhibits remarkable ecological versatility, with larvae inhabiting diverse aquatic and terrestrial environments from Antarctic glaciers to tropical lakes. Males possess distinctive plumose antennae. Larvae of some species contain hemoglobin analogs that produce bright red coloration, earning them the common name 'bloodworms.'
Ephemeroptera
mayflies, Canadian soldiers, shadflies, fishflies, up-winged flies
Mayflies (Ephemeroptera) represent the oldest known winged insects, with fossil evidence dating to approximately 350 million years ago in the lower Carboniferous. The order contains over 3,000 described species across more than 400 genera and 42 families worldwide. Adults are characterized by short lifespans—typically hours to days—and a unique subimaginal stage where the winged but sexually immature subimago undergoes a final molt to become a reproductive imago. Larvae are exclusively aquatic and serve as important indicators of water quality in freshwater ecosystems.
Ephoron album
Say's Burrowing White Mayfly, White Fly
Ephoron album is a burrowing mayfly native to eastern and central North America, notable for synchronized mass emergences ('superhatches') involving millions of individuals in late summer evenings. Adults have pale milky-white wings and live less than 24 hours without feeding. Nymphs inhabit silty riverbeds and develop for several months to one year before emergence. The species was first described by Thomas Say in 1823 during the Long expedition to the Mississippi headwaters.
Hexagenia atrocaudata
Lake Hex
Hexagenia atrocaudata is a burrowing mayfly species in the family Ephemeridae, known from North American lakes and rivers. As a member of the common burrower mayflies, it spends the vast majority of its life as an aquatic nymph in bottom sediments, emerging as a short-lived winged adult for reproduction. Adults lack functional mouthparts and do not feed. Mass synchronous emergences can occur, producing swarms that attract fish and anglers alike. The species serves as an important indicator of clean freshwater ecosystems and provides substantial food resources for aquatic and terrestrial predators.
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 limbata
Giant Mayfly, Golden Mayfly, Big Michigan Mayfly, Great Leadwing Drake, Fishfly
Hexagenia limbata is a large burrowing mayfly native to North America, widely distributed across lakes and slow-moving rivers. Nymphs construct U-shaped burrows in muddy substrates and serve as important prey for fish and other aquatic predators. Adults emerge in synchronized mass events known as "hatches," living only 1–3 days without feeding, solely to mate and reproduce. The species is economically significant to sport fishing and serves as a bioindicator of clean freshwater ecosystems.
Ithonidae
moth lacewings, giant lacewings
Ithonidae is a small family of neuropteran insects comprising ten living genera and over a dozen extinct genera known from fossils. The family represents one of the most primitive lineages within Neuroptera. Adults are medium to large-sized with distinctive wing venation. Larvae exhibit a highly unusual grub-like (scarabaeiform) body form with stout mandibles, unique among lacewings, and lead a subterranean lifestyle. The modern distribution is notably disjunct, with genera occurring in Australia, the Americas, and Asia, while fossil evidence indicates a formerly broader global range from the Early Jurassic to Late Eocene.
Magicicada
Periodical Cicadas
Magicicada is a genus of periodical cicadas found in eastern North America, comprising seven species that emerge in synchronized mass events after 13- or 17-year underground development periods. These cicadas are among the longest-lived insects, spending nearly their entire lives as nymphs feeding on tree root xylem before emerging to molt, mate, and die within weeks. The genus is famous for its prime-numbered periodicity, predator satiation strategy, and the formation of distinct geographic broods that emerge on different schedules.
Megapurpuricenus
Megapurpuricenus is a monotypic genus of long-horned beetles in the family Cerambycidae, established by Eya in 2015. The sole described species, M. magnificus, is notable for its spectacular appearance and highly synchronized emergence pattern. Adults emerge en masse every three years for approximately two weeks following the first summer monsoon rains, creating a brief but intense reproductive window. The genus is endemic to a limited number of locations in the southwestern United States, where it develops as larvae in the trunks of living oak trees.
Megapurpuricenus magnificus
Texas Canyon Longhorn Beetle
Megapurpuricenus magnificus is a spectacular longhorn beetle (Cerambycidae) known for its massive size and striking red-and-black coloration. It is the sole species in its genus and exhibits a remarkable synchronized mass emergence every three years following the first summer monsoon rains. Adults are powerful fliers that congregate high in oak canopies for a brief reproductive period lasting approximately two weeks. The species has an extremely restricted distribution, occurring only in a few canyon systems in southeastern Arizona and historically in the Huachuca Mountains.
Neotibicen canicularis
dog-day cicada, dog-day harvestfly, heatbug, Northern Dog-day Cicada
Neotibicen canicularis is an annual cicada species found across much of North America, commonly known as the dog-day cicada or dog-day harvestfly. Unlike periodical cicadas that emerge in synchronized broods every 13 or 17 years, this species appears every summer, though individuals require several years to develop underground. Adults are active during the hot midsummer period traditionally called the "dog days." The species has been documented as a host for multiple flesh fly parasitoids in the family Sarcophagidae, including several first-record associations.
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Little Specklewings
Pacarina is a genus of cicadas in the family Cicadidae, distributed in the Neotropical region. The genus remained poorly known until 2020, when the first definitive host plant and rearing records were published. Twenty-nine adults emerged from the soil of a potted Dracaena trifasciata plant in Panama, revealing that nymphs develop underground feeding on host plant roots. These reared specimens likely represent an undescribed species, highlighting how much remains unknown about this genus.
Plecia nearctica
lovebug, honeymoon fly, double-headed bug
Plecia nearctica, commonly known as the lovebug or honeymoon fly, is a march fly (family Bibionidae) native to parts of Central America and the southeastern United States. The species is renowned for its mass synchronous emergences of adults, which form conspicuous mating swarms along highways and roads. Males and females remain coupled in copula for 2–3 days, often flying while attached. Adults do not feed and rely entirely on fat reserves accumulated during larval development. The species has expanded its range northward since its original description from Louisiana and Mississippi in 1940.
Smicridea fasciatella
net-spinning caddisfly
Smicridea fasciatella is a net-spinning caddisfly in the family Hydropsychidae. It is the primary species responsible for nuisance swarming events along the Colorado River in Bullhead City, Arizona, where synchronized mass emergence of adults creates significant quality-of-life impacts for residents. The species belongs to the fasciatella species group, which occurs across the Americas from the southwestern United States through Central America and South America. Like other hydropsychid caddisflies, its larvae are aquatic filter-feeders that construct capture nets to obtain food from flowing water.