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Great Lakes Waterlife Photo Gallery
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Some Ephemeroptera nymphs are common in the deep profundal benthic zones of the Great Lakes - others are restricted to littoral or tributary benthos. Winged adults are usually found floating on the water surface, associated with emergent macrophytes (e.g., wetlands) or in nearshore terrestrial habitats. Ephemeroptera live most of their lives as nymphs with a very brief adult stage (mate and die). Mayflies are unique among insects in that they molt once as an 'adult' - thus having 2 winged stages. The subimago or dun is a shortlived stage usually at the water surface. The imago or spinner is the final form which participates in the mating flight. Adults usually lack a mouth and so are incapable of eating (or biting) and generally live less than 3 days after emergence. Ephemeroptera exhibit swarming behavior in which emergence (transformation of aquatic nymphs to flying adults) is strongly coincident (all the nymphs of the right age in an area transform within days of each other). Both nymphs and emergent adults are an imporant source of food for fish.
Morphologically-based taxonomy under revision due to recent/ongoing genetic studies.
Pictoral Guide to Anatomical
Terms Used in the Following Keys: 
Fishermonk
- Mayfly Anatomy
The following taxonomic keys were consulted in the development of the Great Lakes keys on this page:
Aquatic
Insects of Michigan
Short
Key to Mayfly Genera
Ephemeroptera Nymphs - Key
to the 9 Great Lakes Families |
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dorsal surface of the thorax expanded (covering gills) into a broad shield - usually with points to the sides, extremely hump-backed |
Leptohyphidae gills hidden (pair on the second segment modified to form a triangular cover) |
Caenidae brown, gills hidden (pair on the second segment modified to form a square cover), legs sprawling |
Tusks. Visible gills on segments 2-7 each in 2 feathery branches held vertically over the back. |
4 visible pairs of gills (no gills on segment 2, usually none on 1 or 3, 5th pair small and hidden beneath 4th) - not held dorsally. Each gill a flat plate. |
Heptageniidae Head and body both flattened. Large dorsal eyes. 7 pairs of gills each consisting of 1 flat plate with a tuft. Legs sprawling |
greenish, <10mm, gills in 1-2 oval or heart-shaped plates. Abdomen without spines. Tails fringed with setae along the length (on the two external tails, fringes toward the inside only). Legs ventral rather than to the side (swimmers). |
7 pairs of gills. Each Gill forms 2 straps or a tapering plate or a small base with radiating filaments. Tails equal to or longer than body and each with hairs at the end (not a fringe along the length). Legs ventral rather than to the side (swimmers). |
Gills of the 1st segment on the bottom of the segment. Gills flat with tufts. long slender hairs on the inside of the front legs. No tusks. tails with dense fringe on inside edges. |
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mandibular tusks have spines on the top surface and are not curved upward |
Frontal prominence of head deeply forked |
Frontal prominence of head rounded; Mandibular tusks long and upcurved, with tips divergent |
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Sides of abdominal segment 9 don't extended to the tails |
Abdominal segment 9 longer than 8 |
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Gills of all segments platelike
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 Stenonema Gills of abdominal segment 7 slender, fingerlike Strong dark/light color pattern on body |
Key NA |
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Double-strap shaped gills, 3 equal tails |
single plate-like gills, hindwing pad present, very short middle tail |
double heart-shaped gills, hindwing pad present, |
single plate-like gills, hindwing pad present, 3 equal tails |
single plate-like gills, no hindwing pad, only 2 tails |
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only gills on segment 1 deeply cleft appearing as 2 straps |
all gills deeply cleft appearing as 2 straps |
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The following taxonomic keys were consulted in the development of the above Great Lakes guide:
American
Museum of Natural History - Key to Insect Orders
VCSU
- Macroinvertebrate Lab - Key to Aquatic Larval Insects
Aquatic
Invertebrates Illustrated Field Guide
An
Introduction to Insect Life Cycles
Ephemeroptera
Iowa
Water - Benthic Macroinvertebrate Key
Short
Key to Mayfly Genera
Pacific
Northwest Mayflies
Guide
to the Aquatic Invertebrates of the Upper Midwest - Ephemeroptera
An
Identification guide to the Nymphal Mayflies (Order EPHEMEROPTERA)
of British Columbia
Key to Adult (Imago/Subimago) Ephemeroptera |
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Ephemeroptera Adults - Key to Great Lakes Families Typical keys to the adult (imago/subimago) forms of mayflies rely heavily on patterns of veins in the forewings for identification. A good hand lens is a necessity for proper identification. For identification purposes: indicates a unique feature & indicates an important feature Anatomical Drawings: |
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Body: 6-9mm. Thorax unusually large (stout) & abdomen tapers sharply in its rear half (Abdominal segments 6 and 7 wider, longer, and higher in profile view than segments 5 and 8). Tail: 2-3, 3rd (middle) tail is very short or absent Wings: Hindwings variable, may be reduced or absent, if present almost circular in shape. Venation: Vein MP2 not bent, not parallel with CuA near wing base, from vein MP1; vein MP2 only may diverge from MP1. Cubital intercalaries absent with vein A1 terminating in outer margin of wings. |
Leptohyphidae Color: Black insect with white wings - thorax may actually be blackish, dark grey or dark brown. Body: <4mm. Bodies have a heavy thorax Tails: 3 Wings: hindwings absent. Forewings longer in relation to width than Caenidae Venation: Vein MA forming a more or less symmetrical fork, and veins MP2 and IMP extend less than three-fourths of distance to base of vein MP. |
Color: Wings whitish. Thorax usually brown. Body: <4mm. Robust
thorax, small abdomen Tails: 3 Wings: hindwings absent. Forewings shorter in relation to width than Leptohyphidae Venation: MA2 attached basally by a crossvein, and veins MP2 and IMP almost as long as vein MP extending nearly to base. |
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Color: Abdomen of most species with striking dark pattern - except Ephoron which is yellow shaded with tan. Body: 12-40mm. Tails: 2-3 Wing: Hindwings present. Costal angulation of hindwings usually rounded, but may be nearly acute or at right angles Venation: Base of vein MP2 sharply bent near the wing base towards CuA and sometimes fused at base with CuA. Vein A1 forked near margin and outer margin with dense network of reticulate veinlets (Ephoron) OR vein A1 unforked, attached to hind margin by three or more veinlets. |
Body: 4-15mm. Tails: 3 Wings: Hind wings usually large, with a pronounced angle on the fore margin. Costal projection shorter than wing width. Venation: Vein MP2 not bent, not parallel with CuA near wing base; vein MP2 only may diverge from MP1. One or two long intercalary veins between MP2 and CuA. Cubital intercalaries variable, but not as a series of veinlets or attaching vein CuA to hind margin. Short, basally detached marginal intercalaries present between veins along entire outer margin of wings.
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Body:4-20mm. Tails: 2 Wings:Hindwings large Venation: Vein MP2 not bent, not parallel with CuA near wing base; vein MP2 only may diverge from MP1. MA2 and MP2 attached basally. 2 pairs of cubital intercalaries present with vein A1 terminating in hind margin of wings.
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Body: 4-20mm. Abdominal segments ~ equal. Tails: 2 Wings: Hind wings <1/2 long as forewings or absent. Costal projection of hindwings acute. Venation: Vein MP2 not bent, not parallel with CuA near wing base. Veins MA2 and MP2 may be detached basally from their respective sterns. Cubital intercalaries (A) consist of a series of veinlets, often forking or sinuate, attaching vein CuA to hind margin OR (B) with vein A1 terminating in hind margin of wings OR (C) absent. Short, basally detached, single or double marginal intercalaries may be present in each interspace. |
Body: 4-12mm. Tails: 3 Wings: Hind wings present and usually relatively large but without a pronounced angle on the fore margin. Costal projection shorter than wing width. Venation: Vein MP2 not bent, not parallel with CuA near wing base; vein MP2 only may diverge from MP1. 1-2 pair of cubital intercalaries, but not attaching vein CuA to hind margin nor two pairs in which the anterior pair is long and the posterior pair very short nor Vein A-I attached to hind margin. True basally detached marginal intercalaries usually absent along entire outer margin of wings. |
Body: 9-17mm, dark Forewing venation greatly reduced, apparently only three or four longitudinal veins behind R1. |
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11-13mm, legs feeble, mostly non-functional. Wings often somewhat translucent and colorless or with gray or purplish gray shading. |
15-20mm, legs functional; spotted wings; 3 tails of equal length |
30-40mm, legs functional; wings hyaline without spots, 2 tails (or middle very short), body yellow-light brown and patterned. |
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3 tails of equal length |
NA |
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4-12mm, Wings may have crossveins below bullae clouded, but not dark. Basal crossveins between R1 and R2 rarely margined. Penes not L-shaped |
6-20mm, Wings may have crossveins below bullae clouded, but
not dark. Basal crossveins between R1 and R2 rarely margined.
Penes more or less L-shaped |
~13mm, Wings with 2-3 crossveins below bullae between veins R1 and R2 connected or nearly connected by dark pigmentation, rarely only a dark spot. Basal crossveins between R1 and R2 dark margined. |
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9mm. Cubital intercalaries of forewing consist of a series of veinlets, often forking or sinuate, attaching vein CuA to hind margin. |
4-10mm. Both fore and hind wings with few crossveins. Marginal veinlets of forewing in pairs. |
Hindwings minute with an obtuse costal angulation. Both fore and hind wings with numerous crossveins. Body appears freckled. |
Hindwings small w/hooked costal angulation. Both fore and hind wings with few crossveins; Marginal veinlets of forewing single. |
4-6mm. No hindwings |
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10-12 mm; body robust; the middle tail is shorter and thinner than the outer ones. |
4-8 mm; body slender; 3 tails about equal in length and thickness. Brown or pale in color. |
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