Stream-ecology
Guides
Acroneuria carolinensis
Carolina Stone
Acroneuria carolinensis, commonly known as the Carolina stone, is a predatory stonefly in the family Perlidae. It has a univoltine life cycle with emergence from late May through mid-July. Nymphs undergo an ontogenetic habitat shift, moving from leaf packs in slow water as small instars to cobble substrates in riffles as they grow larger. Adults are short-lived, do not feed, and are attracted to lights. The species functions as a top invertebrate predator in stream ecosystems.
Arctopsyche grandis
netspinning caddisfly
Arctopsyche grandis is a species of netspinning caddisfly in the family Hydropsychidae, found in North America. Larvae construct silk nets to capture food in flowing water and complete their development in approximately one year. The species has been studied in Central Idaho streams where it reaches high population densities on rocky substrates.
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.
Capniidae
small winter stoneflies, winter stoneflies
Capniidae, the small winter stoneflies, is one of the largest families in the order Plecoptera, comprising approximately 300 species distributed throughout the Holarctic region. Adults are active during winter months, often observed on snow-covered stream banks when most other insects are dormant. The family exhibits notable adaptations to cold environments, including antifreeze compounds and winglessness in some species, which has led to high endemism and restricted distributions. Their closest relatives are the rolled-winged stoneflies (Leuctridae).
Ceraclea
long-horned caddisfly
Ceraclea is a genus of long-horned caddisflies (family Leptoceridae) containing over 140 described species. Larvae are aquatic and construct portable cases using silk and various materials. Multiple species have been documented as freshwater sponge specialists, though feeding habits vary including detritivory. Life cycles range from univoltine to more complex multi-cohort patterns with variable overwintering strategies.
Corydalinae
Dobsonflies
Corydalinae is a subfamily of large megalopteran insects commonly known as dobsonflies. Adults are among the largest winged insects in their range, with males of some species possessing dramatically elongated mandibles used in intraspecific combat. Larvae, called hellgrammites, are aquatic predators inhabiting clean, fast-flowing streams. The subfamily contains nine genera distributed across the Americas, Asia, and South Africa, with notable Oriental genera including Neurhermes and Nevromus. Some Corydalinae species exhibit striking coloration patterns that likely represent Batesian mimicry of diurnal toxic moths.
Corydalus cornutus
Eastern Dobsonfly, Hellgrammite (larval form), Go-devil, Grampus
Corydalus cornutus, the eastern dobsonfly, is among the largest insects in eastern North America, with adults reaching 140 mm in length and wingspans up to 130 mm. The species exhibits pronounced sexual dimorphism: males possess elongated, sickle-shaped mandibles up to 40 mm long used in combat with rivals, while females have shorter, powerful mandibles capable of delivering a painful bite. The aquatic larval stage, known as hellgrammites, are apex invertebrate predators in fast-flowing streams, feeding on other aquatic insects for one to three years before emerging to pupate in terrestrial soil chambers. Adults are short-lived, non-predatory, and primarily nocturnal, attracted to lights near waterways.
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.
Epeorus longimanus
flatheaded mayfly
Epeorus longimanus is a flatheaded mayfly species in the family Heptageniidae. Nymphs inhabit stream riffles and show specific microhabitat preferences, being more abundant in areas with smaller sediment sizes, higher live periphyton biomass, and lower densities of invertebrate predators. The species is distributed across western North America from Alaska through the western United States to southwestern and northern Canada.
Ephemerella maculata
spiny crawler mayfly
Ephemerella maculata is a species of spiny crawler mayfly in the family Ephemerellidae. It exhibits a migratory life cycle involving upstream flight of adults, downstream drift of nymphs, and upstream crawling by nymphs to compensate for displacement. The species is found in North American streams.
Gammarus pseudolimnaeus
Northern Spring Amphipod
Gammarus pseudolimnaeus is a freshwater amphipod crustacean inhabiting lotic (flowing water) environments in North America. The species exhibits complex behavioral ecology, including size-selective predation vulnerability to fish predators such as brook trout and sculpins, and chemically-mediated responses to predation risk that influence reproductive behavior. Population dynamics are characterized by univoltine (single annual) generation cycles with high mortality during early life stages and winter periods. The species serves as an important prey item in stream food webs and has been extensively studied as a model organism for freshwater invertebrate ecology, toxicology, and predator-prey interactions.
freshwaterloticamphipodpredator-preybehavioral-ecologytoxicologyunivoltineNorth-Americamodel-organismstream-ecologysize-selective-predationchemical-ecologyparasitismacanthocephalacopper-toxicitymate-guardingcalceolimicrohabitat-selectionthigmotaxisdiel-activityseasonal-dynamicsproduction-ecologydriftbrook-troutsculpinOntarioVirginiaGammaridaecrustaceaninvertebratesenticaudataBousfield-1958Northern-Spring-AmphipodGlossosoma nigrior
little black caddisfly
Glossosoma nigrior is a caddisfly species in the family Glossosomatidae, commonly known as the little black caddisfly. It is native to North America and has been extensively studied in Michigan trout streams and Alabama streams. The species exhibits respiratory adaptations to flowing water conditions and serves as a dominant benthic grazer in stream ecosystems.
Glossosomatidae
tortoise-case makers, saddle-case makers, little black caddisflies
Glossosomatidae is a family of caddisflies (order Trichoptera) containing 23 genera across three subfamilies. Larvae construct distinctive domed cases from pebbles bound with silk, giving rise to the common names "tortoise-case makers" or "saddle-case makers." The family has a worldwide distribution with particular diversity in the Americas. Larvae are primarily found in cool, fast-flowing streams where they serve as important bioindicators of water quality due to their sensitivity to pollution and long aquatic life stages.
Goeridae
Armour-ballast Caddisflies
Goeridae is a family of caddisflies (Trichoptera) comprising approximately 12 genera and at least 160 described species. Larvae are primarily lotic, inhabiting streams and rivers, with some species occupying madicolous habitats such as wet cliff faces. The family is distinguished by larval case construction incorporating ballast stones for weight and stability. Adults exhibit highly modified male genitalia and maxillary palps in some species. Goeridae has a Holarctic distribution with records from North America, Europe, and Asia.
Habrophlebia vibrans
pronggilled mayfly
A small stream-dwelling mayfly with a 2-year life cycle, notable for its extended development compared to most mayflies. Adults emerge synchronously in June. Nymphs inhabit gravel substrates and show distinct drift patterns across life stages. The species has been studied in Québec populations, where it reaches final sizes of approximately 5 mm before emergence.
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.
Homoplectra
homoplectran caddisflies
Homoplectra is a genus of netspinning caddisflies in the family Hydropsychidae, established by Ross in 1938. The genus comprises approximately 11 described species distributed in North America and Japan. As members of Hydropsychidae, larvae construct fixed capture nets to filter food from flowing water. The genus includes the recently described species H. gracilis from Japanese headwater streams.
Hydropsyche occidentalis
Hydropsyche occidentalis is a filter-feeding caddisfly species in the family Hydropsychidae, found in lotic (flowing water) streams of North America. It constructs fixed capture nets to filter organic particles from the water column, playing a significant role in stream ecosystem function. The species has been studied for its bioenergetics and contribution to controlling organic transport in streams, where it can comprise a substantial portion of invertebrate biomass in suitable habitats.
Hydropsychidae
Net-spinning Caddisflies
Hydropsychidae, commonly known as net-spinning caddisflies, is a family of aquatic insects in the order Trichoptera. Larvae construct silk nets at the openings of their retreats to capture food particles from flowing water. The family is globally distributed in freshwater habitats and serves as important bioindicators of stream health. Larvae exhibit unique behaviors including territorial defense through stridulation and competitive interactions for retreat ownership.
Isoperlinae
Stripetail Stoneflies, Springflies
Isoperlinae is a subfamily of stoneflies in the family Perlodidae, distributed across the Palaearctic and Nearctic regions. Members are commonly known as stripetails or springflies. The subfamily includes approximately 12 genera, with Isoperla being the most speciose and well-known. These stoneflies are aquatic insects whose nymphs inhabit running waters.
Lara avara
riffle beetle
Lara avara is a xylophagous riffle beetle in the family Elmidae. It inhabits freshwater streams in western North America, where larvae feed on submerged decaying wood. The life cycle spans 4–6 years, with extended larval development and brief adult emergence from May to August. The species contributes to aquatic wood decomposition through larval feeding and fecal production.
Micrasema
humpless casemaker caddisflies
Micrasema is a genus of caddisflies (order Trichoptera) in the family Brachycentridae, commonly referred to as humpless casemaker caddisflies. The genus contains more than 70 described species. Larvae are aquatic and construct portable cases from plant material. At least one species, Micrasema quadriloba, has been studied as a grazing insect in stream ecosystems.
Naucoridae
creeping water bugs, saucer bugs
Naucoridae is a family of aquatic predatory true bugs comprising approximately 400 species in 46 genera across five subfamilies. Members are commonly known as creeping water bugs or saucer bugs due to their dorsoventrally flattened, oval body shape. They inhabit freshwater environments worldwide with greatest diversity in tropical regions, ranging from still waters to torrential streams. Most species are lotic, occurring in flowing waters rather than lentic habitats. They are predatory, feeding on other small invertebrates using piercing-sucking mouthparts.
Ostrocerca
forestflies
Ostrocerca is a genus of spring stoneflies (Plecoptera) in the family Nemouridae, containing six described species distributed in eastern North America. Members are small to medium-sized stoneflies commonly known as forestflies. The genus was established by Ricker in 1952. Species are distinguished by subtle morphological differences in wing venation and genitalia.
Paracapnia
small winter stoneflies
Paracapnia is a genus of small winter stoneflies in the family Capniidae, native to North America. The genus contains at least five described species, including the angulate snowfly (Paracapnia angulata) and the northeastern snowfly (Paracapnia opis). Members of this genus are notable for their tolerance of acidic stream conditions, with some species increasing in abundance in waters affected by acid precipitation.
Phanocerus clavicornis
riffle beetle
Phanocerus clavicornis is a small riffle beetle in the family Elmidae, measuring approximately 3 mm in length. The species exhibits a broad Neotropical distribution, ranging from Texas and the Caribbean through Central America to southeastern Brazil. Populations in Atlantic Rainforest streams demonstrate significant phenotypic plasticity in body size in response to hydraulic conditions, with smaller larvae occurring during periods of greater rainfall. Both larvae and adults are fully aquatic and occupy the same freshwater environments.
Plecoptera
stoneflies
Plecoptera, commonly known as stoneflies, comprises approximately 3,500 described species worldwide. This order represents one of the most primitive groups of Neoptera, with fossil relatives dating to the Carboniferous and Lower Permian periods, though modern diversity appears to be of Mesozoic origin. Stoneflies are found on every continent except Antarctica, with distinct populations in the Northern and Southern Hemispheres. All species are aquatic in their immature stages and are highly sensitive to water pollution, making them important bioindicators of stream and river health.
Potamyia
netspinning caddisflies
Potamyia is a genus of netspinning caddisflies in the family Hydropsychidae, containing more than 20 described species. Larvae are aquatic and inhabit streams, with five instars characterized by progressive increases in head capsule width. They are omnivorous filter-feeders that consume diatoms, green algae, filamentous algae, detritus, and arthropod fragments. The genus is distributed across Asia, with documented species in Thailand, China, and other regions.
Psephenus
water penny beetles
Psephenus is a genus of water penny beetles comprising approximately 13 described species. Larvae are aquatic, highly flattened, and cling to submerged stones in streams using ventral sucking discs. Adults are terrestrial, do not feed, and aggregate near water for mating. The genus exhibits strong associations with stream riffles and turbulent water environments.
Pycnopsyche gentilis
caddisfly
Pycnopsyche gentilis is a northern caddisfly in the family Limnephilidae. Larvae are shredders that inhabit allochthonous organic materials in freshwater streams, where they feed on leaf litter colonized by aquatic fungi. The species is contemporaneous with congeneric P. luculenta, though larvae differ in case materials and habitat preferences. Adult males exhibit temporal partitioning of flight activity, with distinct peak arrival times at light sources when active on the same night as congeners.
Pycnopsyche lepida
northern caddisfly
Pycnopsyche lepida is a species of northern caddisfly in the family Limnephilidae. It is found in North America. Larval ecology has been studied in Michigan streams, where microdistribution is limited by physical habitat factors.
Scirtidae
Marsh Beetles
Scirtidae is a family of small beetles commonly known as marsh beetles. Larvae are typically associated with stagnant water but can also occur in flowing water, while adults are found near water's edge in decomposing plant material. The family comprises more than 600 described species distributed among approximately 30-60 genera worldwide. Members are primarily aquatic or semi-aquatic in their larval stages, with adults showing strong affinity for moist riparian habitats.
Torrenticola
Torrenticola is a genus of water mites in the family Torrenticolidae, comprising over 400 described species globally and 90 species in North America alone. These mites are characteristic inhabitants of rocky and sandy streams, where they represent the dominant water mite genus. Recent taxonomic work has demonstrated that color markings, long overlooked by traditional acarology, serve as valuable diagnostic characters for species identification when combined with DNA sequencing and morphological analysis.
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.
Xylotopus par
Xylotopus par is an aquatic xylophagous midge in the family Chironomidae. The larvae colonize submerged wood substrates in freshwater streams, feeding on decaying wood. Populations exhibit plastic phenology, with development rates varying based on wood substrate quality—larvae in fresh, introduced wood can complete development in a single summer, while those in indigenous logs normally require a full year. The species has been studied for its unique bacterial associations in the larval midgut, where morphotypically uniform bacteria form a well-defined band in the posterior midgut's ectoperitrophic space.
Zapada cordillera
Cordilleran Forestfly
Zapada cordillera is a species of spring stonefly in the family Nemouridae, commonly known as the Cordilleran Forestfly. Described in 1971 from specimens in the western United States, this small aquatic insect is part of a genus whose nymphs are characterized by distinctive branched cervical gills retained into adulthood. As a member of the Nemouridae, it contributes to stream ecosystem function as a leaf-shredding detritivore and serves as an indicator of water quality in its montane habitat.