Aquatic Insects of Michigan
by Ethan Bright, Museum of Zoology Insect Division and School of Natural Resources and Environment
University of Michigan
- Home
- Species Lists
- Coleoptera
- Diptera
- Ephemeroptera
- Acanthametropodidae
- Ameletidae
- Ametropodidae
- Arthropleidae
- Baetidae
- Baetiscidae
- Behningiidae
- Caenidae
- Ephemerellidae
- Ephemeridae
- Heptageniidae
- Isonychiidae
- Leptohyphidae
- Leptophlebiidae
- Metretopodidae
- Neoephemeridae
- Oligoneuriidae
- Palingeniidae
- Polymitarcyidae
- Potamanthidae
- Pseudironidae
- Siphlonuridae
- Heteroptera
- Hymenoptera
- Lepidoptera
- Megaloptera
- Neuroptera (Sisyridae)
- Odonata
- Orthoptera
- Plecoptera
- Trichoptera
- Other Orders
- Keys/Identification
- Aquatic Insects of Michigan
Introduction to the Ephemeroptera (Mayflies) of Michigan
Mayflies are most familar to people for their brief adult life stage, usually 1-4 days, although for some species it is very brief (e.g., Ephoron ca. 1 hour!). Ephemeroptera is an ancient paleopteran insect family, being older than the Odonata, with fossils appearing in Devonian rocks but appears more abundant in the Carboniferous and especially the Permian rocks. Today, although probably past their heyday in terms of species (now about > 2000 species), mayflies are still important in aquatic ecosystems, especially for fisheries in terms of periphyton and detrital processing, and are often abundant.
Mayflies are typical hemimetabolous insects (egg -> nymph -> adult), with the exception of a unique (among insects), winged, non-sexual stage (subimago, or "dun" among fly-fishers) prior to the sexually mature winged stage (imago, or "spinner") (nymph -> subimago ->imago). Adults are recognized by 2 pairs of wings held vertically on the back, although the hind pair is reduced or absent in some species. Eyes may be sexually dimorphic (many species), with males having well-developed sight (sometimes 360°) for mating with females on the wing. Mouthparts and digestion tract are degenerate in the adult stage.
The nymph stage usually lasts from 2 months to 2 years, with about 20-30 instars, depending on species and usually temperature. The last nymphal instar sees a quiescent degeneration with a breakdown of the digestion tract. The nymph-subimago transition occurs in water, and is very vulnerable to predators, which is why mayflies are such good fish bait. Wing pads must rapidly be inflated with hemolymph (about 2-3 minutes). In the Ephemerellidae, a common trout stream mayfly, hydrofuge hairs keep water away from the subimago body, permitting partial inflating as it rises to the water's surface. For some very shortlived adult stages, the subimago molt is incomplete and the whitish subimago cuticle remains with the adult body. The subimago looks like an adult, but usually has shorter legs and cerci, smokier wings due to 2 cuticle layers scattering light, less colorful bodies, and having sexual organs not fully ready. This "pre-adult" stage is short, usually lasting overnight. The adult "spinner" stage see a swarming mating ritual.
Adults are shortlived, mating once and dying. Swarming functions for mates to find each other. Males congregate around a characteristic structure, such as a tree, flying up and down in a characteristic, specieis-specific pattern.
Adults (adapted from Edmunds and Waltz 1996)
| 1a | a. Forewing venation greatly reduced, apparently only three or four longitudinal veins behind R1 | Oligoneuriidae, Homoeoneuria ammophila (Spieth) |
| b. Body dark | ||
| 1b | a. Forewing venation complete or moderately reduced, numerous longitudinal veins present behind R1 | 2 |
| b. Body color variable | ||
| 2a | a. Penes of male longer than forceps | Behningiidae, Dolania americana Edmunds and Traver |
| b. Antennae of female inserted on prominent anterolateral projections | ||
| c. Intercalary behind CuA of forewing subparallel to and almost as long as CuA, attached to CuA by seven or more unbranched crossveins | ||
| 2b | a. Penes of male shorter than forceps | 3 |
| b. Antennae of female not inserted as above | ||
| c. Intercalaries behind CuA variable; intercalary behind CuA much shorter, with few or no crossveins attaching it to CuA, or crossveins anastomosed, especially near wing margin | ||
| 3a | a. In forewings, base of veins MP2 and CuA strongly divergent from base of vein MP1 | 4 |
| b. MP2 strongly bent twoards CuA basally and sometimes fused at base with CuA | ||
| c. hind wings with numerous veins and crossveins; vein MA of hindwings unforked | ||
| 3b | a. In forewings, base of veins MP2 and CuA little divergent from vein MP1 (vein MP2 only may diverge from MP1), fork of MP usually more symmetrical | 7 |
| b. Hindwings variable, may be reduced or absent | ||
| c. If hind wings present, vein MA variable | ||
| 4a | a. Costal angulation of hindwings acute or at a right angle | Neoephemeridae, Neoephemera bicolor McDunnough |
| b. Forewing vein A1 unforked | ||
| c. Costal crossveins basal of forewing bullae weak or atrophied | ||
| 4b | a. Costal angulation of hindwings usually rounded, but if nearly acute or at right angles, froewing vein A1 forked near margin | 5 |
| b. Costal crossveins basal of forewing bullae well developed | ||
| 5a(4b) | a. Middle and hind legs of male and all legs of female feeble and nonfunctional | Polymitarcyidae, Ephoron Williamson |
| b. Color usually pale | ||
| c. Wings often somewhat translucent and colorless or with gray or purplish gray shading | ||
| also: Outer margin of forewing with dense network of reticulate veinlets | ||
| 5b | a. All legs of both sexes well-developed and functional | 6 |
| b. Color variable | ||
| 6a(5b) | a. Forewing vein A1 forked near wing margin | Potamanthidae, Anthopotamus McCafferty and Bae |
| b. Abdomen usually yellowish, in some species with reddish lateral stripes or spots on terga | ||
| 6b | a. Forewing vein A1 unforked, attached to hind margin by three or more veinlets | Ephemeridae |
| b. Abdomen of most species with striking dark pattern on terga and sterna | ||
| 7a(3b) | Cubital intercalaries of forewing consist of a series of veinlets, often forking or sinuate, attaching vein CuA to hind margin | 8 |
| 7b | Cubital intercalaries of forewing variable, but not as above, or sometimes absent | 11 |
| 8a(7a) | a. Remnants of gill tufts (often purplish colored) present at sides of vestigial maxillae and bases of fore coxae | Isonychiidae, Isonychia Eaton |
| b. Forelegs largely or entirely dark and middle and hind legs pale | ||
| c. Vein MP of hind wing forked near margin | ||
| d. Terminal filament vestigial | ||
| 8b | a. No gill tuft remnants on vestigial maxillae and fore coxae | 9 |
| b. Leg color not as above | ||
| c. Vein MP of hindwing forked near base to mid-length | ||
| d. Terminal filament variable | ||
| 9a(8b) | a. Three caudal filaments | Acanthametropodidae, Acanthametropus pecatonica (Burks) |
| b. Terminal filament distinctly longer than tergum 10 | ||
| c. Hind wing 0.5x or more as long as forewings | ||
| Habitat: rare, large rivers | ||
| 9b | a. Two apparent caudal filaments | 10 |
| b. Terminal filament vestigial | ||
| c. Hind wings < 1/2 long as forewings | ||
| 10a(9b) | a. Claws of each pair dissimilar (1 sharp, 1 blunt) | Ameletidae, Ameletus Eaton |
| b. Costal projection of hindwings acute | ||
| 10b | a. Claws of each pair similar, sharp | Siphlonuridae |
| b. Costal projection of hindwings obtuse or weak | ||
| 11a(7b) | Three well-developed caudal filaments and terminal filament present | 12 |
| 11b | Two well-developed caudal filaments present, terminal filament rudimentary or absent | 15 |
| 12a(11a) | a. Hind wings present and usually relatively large with one or more veins forked | 13 |
| b. Costal projection shorter than wing width | ||
| 12b | a. Hind wings small, with two or three simple veins only or absent | 19 |
| b. If hind wing present, costal projection long (1.5-3.0x width of wing) and straight, or recurved | ||
| 13a(12a) | a. Vein A-l of fore wings attached to hind margin by a series of veinlets | Ametropodidae, Ametropus neavei McDunnough |
| b. Two pairs of cubital intercalaries present, anterior pair long, posterior pair very short | ||
| 13b | a. Vein A-I not attached to hind margin as above | 14 |
| b. Cubital intercalaries not as above | ||
| 14a(13b) | a. Short, basally detached marginal intercalaries present between veins along entire outer margin of wings | Ephemerellidae |
| b. Genital forceps of male with one short terminal segment | ||
| 14b | a. No true basally detached marginal intercalaries in positions indicated above, usually absent along entire outer margin of wings | Leptophlebiidae |
| b. Genital forceps of male with two or three short terminal segments | ||
| 15a(11b) | a. Hind wings with numerous. long, free marginal intercalaries | Baetiscidae, Baetisca Walsh |
| b. Cubital intercalaries absent in fore wings with vein A1, terminating in outer margin of wings | ||
| 15b | a. Hind wings not as above, sometimes absent | 16 |
| b. Cubital intercalaries present in fore wings with vein A1 terminating in hind margin of wings | ||
| 16a(15b) | a. Short, basally detached, single or double marginal intercalaries present in each interspace of fore wings | Baetidae |
| b. Veins MA2 and MP2 detached basally from their respective sterns, hind wings small or absent | ||
| c. Penes of male membranous | ||
| d. Upper portion of eyes of male turbinate (raised on a stalk like portion) | ||
| 16b | a. Marginal intercalaries attached basally to other veins | 17 |
| b. MA2 and MP2 attached basally, hind wings relatively large | ||
| c. Penes of male well developed | ||
| d. Eyes of male not turbinate | ||
| 17a(16b) | a. Hind tarsi distinctly five segmented | Heptageniidae and Arthropleidae |
| b. Tarsi shorter than tibiae | ||
| c. Cubital intercalaries consist of two pairs similar to figure | ||
| 17b | a. Hind tarsi apparently four segmented | 18 |
| b. Basal segment fused or partially fused to tibiae, the fusion line being in basal half of tibiae plus tarsi | ||
| c. Cubital intercalaries consist of one or two pair | ||
| 18a(17b) | a. Eyes of male contiguous (touching) or nearly contiguous dorsally | Metretopodidae |
| b. Fore tarsi 3x length of fore tibiae | ||
| c. Abdomen of female with apical and basal segments subequal to middle segments in length and width | ||
| d. Subanal plate evenly convex | ||
| 18b | a. Eyes of male separated dorsally by twice width of median ocellus | Pseudironidae, Pseudiron centralis McDunnough |
| b. Fore tarsi two times length of fore tibiae | ||
| c. Abdomen of female long and slender, apical segments distinctly more elongate and slender than basal segments | ||
| d. Subanal plate with medial emargination | ||
| Habitat: large, sandy rivers, adults rarely collected | ||
| 19a(12b) | a. Vein MA of fore wings forming a more or less symmetrical fork, and veins MP2, and IMP extend less than three-fourths of distance to base of vein MP | Tricorythidae |
| b. Genital forceps of male two or three segmented | ||
| c. Thorax usually black or gray | ||
| 19b | a. Vein MA of fore wing not as above, MA2 attached basally by a crossvein, wing veins MP2 and IMP almost as lone as vein MP, and extend nearly to base | Caenidae |
| b. Genital forceps of male one segmented | ||
| c. Thorax usually brown | ||
Mature Nymphs
| 1a | Thoracic notum enlarged to form a shield extended to Ab6, gills enclosed beneath sheath |
Baetiscidae, Baetisca Walsh |
| 1b | Thoracic notum not enlarged, anterior abdominal gills exposed | 2 |
| 2a(1b) | a. Gills on Ab2-7 forked and elongate-lanceolate, with margins fringed | 3 |
| b. Usually with mandibular tusks projected forward and visible from above the head | ||
| c. If tusks absent, head and thorax with pads of long spines | ||
| 2b | a. Gills on Ab2-7 variable | 6 |
| b. If gills forked and elongate-lancelotae, margins not fringed | ||
| c. Tusks rarely present on mandibles | ||
| 3a(2a) | a. Head and prothorax with dorsal pad pad of long spines on each side | Behningiidae, Dolania americana Edmunds and Traver |
| b. Without mandibular tusks | ||
| c. Gills ventral | ||
| 3b | a. Head and prothorax without pads of spines | 4 |
| b. Mandibular tusks present | ||
| c. Gills lateral or dorsal | ||
| 4a(3b) | a. Legs unmodified, not expanded | Potamanthidae, Anthopotamus McCafferty and Bae |
| b. Abdominal gills held laterally | ||
| 4b | a. Foretibiae fossorial, more or less modibied, either expanded or with tubercles | 5 |
| b. Abdominal gills held dorsally | ||
| 5a(4b) | a. In lateral view, mandibular tusks curved upright | Ephemeridae |
| b. Ventral apex of hind tibiae projected into distinct acute point | ||
| 5b | a. In lateral view, mandibular tusks not curved upright | Polymitarcyidae, Ephoron Williamson |
| b. Ventral apex of hind tibiae rounded | ||
| 6a(2b) | Double row of long setae on inner margins of femora and tibiae of forelegs | 7 |
| 6b | Long setae absent on forelegs, or not arranged as above | 8 |
| 7a(6a) | a. Gills on Ab1 ventral | Oligoneuriidae, Homoeoneuria ammophila (Spieth) |
| b. Fibrils longer than gill plate | ||
| note: rare | ||
| 7b | a. Gills on Ab1 dorsolateral, similar in position and structure to other gills | Isonychiidae, Isonychia Eaton |
| b. Fibrils shorter than gill plates | ||
| note: Nymphs minnowlike, strong swimmers; common | ||
| 8a(7b) | Gills on Ab2 operculate or semioperculate (covering succeeding pairs) | 9 |
| 8b | Gills on Ab2 neither operculate or semioperculate, either similar to those on succeeding segments, or absent | 11 |
| 9a(8a) | a. Gills on Ab2 triangular or subtriangular, do not meet medially | Leptohyphidae, Tricorythodes Ulmer |
| b. Gill lamellae on Ab3-6 simple, without fringed margins | ||
| also: Forefemora with transverse row of long setae | ||
| 9b | a. Gills on Ab2 quadrate, meeting or almost meeting medially | 10 |
| b. Gill lamellae on Ab3-6 with fringed margins | ||
| 10a(9b) | a. Mesonotum with distinct rounded lobe on anteriolateral corners | Neoephemeridae, Neoephemera bicolor McDunnough |
| b. Operculate gills fused medially | ||
| c. Developing hind wingpads present | ||
| 10b | a. Mesonotum without anterolateral lobes | Caenidae |
| b. Operculate gills not fused medially | ||
| c. Without developing hind wingpads | ||
| 11a(8b) | a. Gills absent from Ab2, rudimentary or absent on Ab1, and present or absent on Ab3 | Ephemerellidae |
| b. Gills on Ab3-7 or 4-7 consist of anterior (dorsal) oval lamella and posterior (ventral) lamella with numerous lobes | ||
| c. Paired tubercles often present on abdominal terga | ||
| 11b | a. Gills present on Ab2, either Ab1-5, 1-7, or 2-7 | 12 |
| b. Paired tubercles rearely present on abdominal terga | ||
| 12a(11b) | a. Body distinctly flattened dorsoventrally | 13 |
| b. Head flattened | ||
| c. Eyes and antennae dorsal | ||
| d. Mandibles not visible in dorsal view | ||
| 12b | a. Body not flattened, or if flattened, mandibles visible and forming part of the flattened dorsal surface of head | 14 |
| 13a(12a) | a. Claws as long or longer than tarsi | Pseudironidae, Pseudiron centralis McDunnough |
| b. Tibiae and tarsi bowed | ||
| Habitat: large sandy rivers | ||
| 13b | a. Claws much shorter than tarsi | Heptageniidae and Arthropleidae |
| b. Tibiae and tarsi straight | ||
| 14a(12b) | a. Claws of forelegs differ in structure from those on middle- and hindlegs | 15 |
| b. Claws of middle and hindlegs long and slender, about as long as tibiae | ||
| 14b | a. Claws of all legs similar in structure, usually sharply pointed, rarely spatulate | 16 |
| b. Claws variable in length, if those of middle and hind legs long and slender, then usually shorter than tibiae | ||
| 15a(14a) | a. Claws on forelegs simple, with long slender denticles | Ametropodidae, Ametropus neavei McDunnough |
| b. Spinous pad present on forecoxae | ||
| 15b | a. Claws on forelegs bifid | Metretopodidae |
| b. Without spinous pad on forecoxae | ||
| 16a(14b) | a. Gills on Ab2-7 either forked, with all margins fringed, or with double lamellae terminated in filaments or points | Leptophlebiidae |
| b. Apicolateral margin of maxillae with a dense brush of hairs | ||
| 16b | a. Abdominal gills not as above, but gills either more or less oval or heart-shaped, and lamellae either single, double, or triple folded, fringed on inner margin in one rare genus, never terminating in filaments or points | 17 |
| b. Apicolateral margin of maxillae variable, but never with a dense brush of hairs | ||
| 17a(16b) | a. Labrum with a median notch on distal margin | Baetidae |
| b. Terminal filament variable, may be shorter than tergum 10 or subequal to cerci | ||
| c. Antennae long, 2-3x or more width of head, or antennae shorter than 2x width of head but with labrum with notched distal margin | ||
| 17b | a. Labrum with a median notch on distal margin | 18 |
| b. Terminal filament subequal to cerci | ||
| c. Antennae shorter than 2x width of head | ||
| 18a(17b) | a. Tibiae and tarsi bowed | Acanthametropodidae, Acanthametropus pecatonica (Burks) |
| b. Claws very long and slender, claws of hindlegs about as long as tarsi | ||
| also: Dorsum of abdomen with median hook-like tubercles; hook-like tubercles also present on each thoracic sternum | ||
| Habitat: rare, in large rivers | ||
| 18b | a. Tibiae and tarsi not bowed | 19 |
| b. Claws usually not long and slender | ||
| 19a(18b) | a. Maxillae with a crown of pectinate spines | Ameletidae, Ameletus Eaton |
| b. Gills with a single lamellae, more or less oval with a sclerotized band along the lateral margin and usually with a similar sclerotized band on or near the mesal margin | ||
| 19b | a. Maxillae without pectinate spines | Siphlonuridae |
| b. Gills variable, not as above | ||
References
Edmunds GF, Waltz RD. 1996. Ephemeroptera, pp. 126-163 in Merritt RW, Cummins KW (editors), An Introduction to the Aquatic Insects of North America, 3rd Edition. Kendall/Hunt Publishing Company: Dubuque, Iowa.
Page created: June 14, 2003 (EB); Last edited: July 29, 2003 (EB)