Aquatic Insects of Michigan

by Ethan Bright, Museum of Zoology Insect Division and School of Natural Resources and Environment
University of Michigan

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Ephemeridae of Michigan - Identification


[under construction]

Adults (adapted from Burks 1953 and Edmunds et al. 1976)

    1a a. Pronotum of male shortened, about three times as wide as long Pentagenia vittigera (Walsh)
    b. Penes long and tubular
    c. Caudal filaments of female shorter than body
    also: large rivers
    1b a. Pronotum of male well developed, no more than twice as wide as long 2
    b. Penes variable, not long and tubular
    c. Caudal filaments of female longer than body
    2a(1b) a. Crossveins of wings crowded together near bullae Ephemera Linnaeus, 3
    b. Fore wings with distinct pattern of dark markings
    c. Terminal filament as long as cerci
    2b a. Crossveins of wings not crowded near bullae 4
    b. Wings without pattern of dark markings although crossveins may be darkened
    c. Terminal filament vestigial or distinctly shorter than cerci

    a. Hind wing with small, dark clouds surrounding the discal crossveins, making the wing appear spotted

    Ephemera simulans Walker
    b. Penis lobes of male relatively broad
    3b a. Hind wing not spotted, discal crossveins not surrounded by dark clouds as above Ephemera varia Eaton
    b. Penis lobes of male relatively narrow
    4a(2a) a. Head with frons greatly expanded below eyes
    Litobrancha recurvata (Morgan)
    b. Scutellum with only a shallow medioapical notch
    c. Penes of male recurved ventrally
    d. Wing uniformly tinted with dark drown
    4b a. Head with frons not extending below eyes Hexagenia Walsh, 5
    b. Scutellum with a deep medioapical notch
    c. Penes of male nor recurved
    d. Wing membrane hyaline or with dark spots or clouds, but never uniformly pigmented as above
    5a(4b) Males 6
    5b Females 8
    6a(5b) In dorsal view, mesal margin of penis lobes with an anteapical protuberance
    Hexagenia bilineata (Say)
    6b In dorsal view, mesal margin of penis lobe without an anteapical protuberance 7
    7a(6b) Apexes of penis lobes sharply incurved
    Hexagenia limbata (Serville)
    7b Apexes of penis lobes elongate and arcuate, tapering gradually to apices Hexagenia rigida McDunnough
    7c Apexes of penis lobes arcuate, but short and blunt Hexagenia atrocaudata McDunnough

    Hind wing with a broad, reddish or purplish-brown band at the posterior margin

    Hexagenia atrocaudata McDunnough

    Hind wing with a relatively narrow, sometimes discontinuous, dark brown band at the posterior margin, and two relatively large, brown sports in the disc of the wing
    Hexagenia bilineata (Say)
    also: Each discal crossvein surrounded by a small, brown cloud
    8c Hind wing without a darkened continuous posterior margin as above 9
    9a(8c) a. Hind wing membrane and veins hyaline, discal crossveins black Hexagenia rigida McDunnough
    b. Abdomen white or cream colored, with dorsal color pattern of dull red markings

    a. Hind wing membrane hyaline, veins partly or entirely yellowish or tan, and cross-veins black or brown both in discal and marginal areas of wing Hexagenia limbata (Serville)
    b. Abdomen yellow, tan or light brown, with a drown color pattern

Nymphs (adapted from McCafferty 1975)

    1a a. Mandibular tusks with a distinct lateral keel that is more or less toothed, and with some spurs
    Pentagenia vittigera (Walsh)
    b. Femora of prothoracic legs produced posteroproximally ventral to trochanters
    c. Terminal segment of labial palpi club-shaped, being broadly rounded apically
    1b a. Mandibular tusks without a distinct toothed keel 2
    b. Femora of prothoracic legs not produced proximally as above
    c. Terminal segment of labial palpi not club-shaped
    2a(1b) a. Frontal process of head distinctly bifurcate Ephemera Linnaeus, 3
    b. Small group of spurs basally and laterally on mandibular tusks
    c. Tibiae of prothoracic legs never emarginate apically, and not greatly flattened
    also: Abdomen with dark, longitudinal markings at least on some abdominal sternites, not appearing flattened or broadened dorsoventrally; caudal filaments no more than one-half the length of the body
    2b a. Frontal process of head rounded or somewhat truncate, never bifurcate 4
    b. Tusks without any spurs or spines
    c. Tibiae of prothoracic legs slightly to distinctly emarginate along the distal margin
    3a(2a) Both fore and hind wing pads heavily blotched with dark markings
    Ephemera simulans Walker
    3b Hind wing pads without dark blotches Ephemera varia Eaton
    also: Dark, longitudinal streaks sometimes discernible laterally along abomen
    4a(2b) a. Antennal segments without whorls of long setae over most of its length, with only short setae Litobrancha recurvata (Morgan)
    b. Small unfringed gills on Ab1 single, not branched
    c. Frontal process of head somewhat angulate with lateral margins slightly divergent from base
    4b a. Antennae with whorls of long setae on most segments Hexagenia Walsh, 5
    b. Small unfringed gills on Ab1 forked
    c. Frontal process of head rounded, conical or truncate
    5a(4b) a. Frontal process more or less truncate, often slightly emarginate Hexagenia atrocaudata McDunnough
    b. Pairs of round or somewhat elliptical, pale, dark margined spots sometimes apparent on both tergites and sternites of abdomen
    5b a. Frontal process not truncate, if anterior margin approaching straight, then lateral margins distinctly convergent anteriorly 6
    b. Never both abdominal tergites and sternites with pairs of pale, dark margined spots
    6a(5b) a. Frontal process narrowly conical Hexagenia rigida McDunnough
    b. Nymph of mature male with distinctive, nearly straight, developing penes
    6b a. Frontal process more or less rounded or broadly conical 7
    b. Nymph of mature male with developing penes curved
    7a(6b) a. Mesotarsal claws swollen for most of their length
    Hexagenia bilineata (Say)
    b. Developing penes of mature male nymph angulate and beak-like
    c. Frontal process sometimes somewhat conical
    7b a. Mesotarsal claws slender for most of their length Hexagenia limbata (Serville)
    b. Developing penes of mature male nymph more evenly curved
    c. Frontal process usually evenly rounded
    Burks BD. 1953. The mayflies, or Ephemeroptera, of Illinois. Illinois Natural History Survey Bulletin 26(1):1-216.
    Edmunds GF, Jensen SL, Berner L. 1976. The mayflies of North and Central America. University of Minnesota Press: Minneapolis, MN. x + 330 p.
    McCafferty WP. 1975. The burrowing mayflies of the United States (Ephemeroptera: Ephemeroidea). Transactions of the American Entomological Society 101:447-504.

Page created: June 16, 2003; Last edited: November 06, 2013 (EB)