Not yet illustrated, Not complete.
1. In forewings, base of veins MP2 and CuA strongly divergent from base of vein MP1; MP2 strongly bent towards CuA basally and sometimes fused at base with CuA; hind wings with numerous veins and crossveins; vein MA of hind wiings unforked. . . . . . . . . . . . . . . . . . . . 2In forewings, base of veins MP2 and CuA little divergent from vein MP1 (vein MP2 only may dirverge from P1), fork of MP usually more symmetrical; hind wings variable, may be reduced or absent, in hind wings present, vein MA variable. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Forewing vein A1 forked near margin; abdomen usually yellowish with reddish or pinkish lateral stripes or spots on terga . . . . . . . . . . . . . . . . . . . Potamanthidae, Anthopotamus
Forewing vein A1 not forked near margin, attached to hind margin by three or more veinlets; abdomen of most speies with distinctive dark contrasting patterns on abdominal terga and sterna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ephemeridae
3. Cubital intcalaries of forewing consist of a series of veinlets, often forking or sinate, attaching vein CuA to hind margin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Cubital intercalaries of forewing variable but not as above; sometimes absent . . . . . . . . . . .5
4. Remnants of gill tufts (often purplish colored) present at sides of vertigial maxillae and bases of forecoxae; forelegs largely or entirely dark and middle and hind legs pale; vein MP of hindwing forked near margin; terminal filament vestigial; widespread and common. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . Isonychiidae, Isonychia
Remnants of gill tufts not preseantr on vestiginal maxillae and forecoxae; leg color not as above; vein MP of hind wing forked near base to mid-length; terminal filament variable . . 10
5. Three well-developed caudal filaments (the cerci and terminal filament) present . . . . . . . . . .6
Two well-developed caudal filaments (the cerci) present, terminal filament rudimentary or absent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
6. Hind wings present and usually relatively large with one or more veins forked; costal projections shorter than wing width . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Hind wings small and with two or three simple veins only or absent; if hind wing present, costal projection long (1.5 times to 3.0 times width of wing) and straight, or recurved . . . . 9
7. Short, basally detached marginal intercalaries present between veins along entire outer margin of wings; genital forceps of male with one short terminal segment . . . . . . . Ephemerellidae
No true basally detached marginal intercalaries in positions indicated above, usually absent along entire outer margin of wings; genital forceps of male with two or three short terminal segments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Leptophlebiidae
8. Hind wings with numerous, long, free marginal intercalaries; cubital intercalaries absent in along entire outer margin of wings; genital forceps of male with two or three short terminal forewings with vein A1 terminating in outer margin of wings . . . . . . . . . . . . . . Baetiscidae
Hind wings not as above, sometimes absent; cubital intercalaries present in forewings with vein A1 terminating in hind margin of wings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
9. Short, basally detached single or double marginal intercalaries present in each interspace of forewings; and veins MA2 and MP2 detached basally from their respective stems, hind wings small or absent; penes of male membranous; upper portion of eyes of male turbinate (raised on a stalk like portion) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Baetidae
Marginal intercalaries attached basally to other veins; MA2 and MP2 attached basally; hind wings relatively large; penes of male well developed; eyes of male not turbinate. Hind tarsae distinctive 5 segmented; tarsi shorter than tibiae; cubital intercalaries consist of two pairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Heptageniidae
10. Vein MA of forewings forming a more or less symmetrical fork, and veins MP2 ad IMP extend less than three-forths of distance to base of vein MP; genital forceps of male two or three segmented; thorax usually black or gray . . . . . . . . . . . . . . . . . . . . . . . . . . Leptohyphidae
Vein MA of forewing not as above, MA2 attached basally by a crossvein; wing veins MP2 and IMP alost as long as vein MP, and extend nearly to base; genital forceps of male one segmented; thorax usually brown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Caenidae
11. Claws of each pair dissimilar (1 sharp, 1 blunt); costal projection of hind wings acute . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Ameletidae
Claws of each pair siilar, sharp; costal projections of hind wings obtuse or weak . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SiphlonuridaeSIMPLE KEY TO FAMILIES OF ADULT MAYFLIES
Modified from Caucci, 2011
1. Two tails (cerci) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Three tails (cerci). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2. Wings clear (may be dark, but not mottled); wing venation not distinct. . . . . . . . . . . . . . . . . 3
Wings mottled; wing venation distinct. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3. No hind wing (Acentrella, Procloeon). . . . . . . . . . . . . . . . . . . . . . . . . . . Baetidae (in part)
Hind wings of various sizes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Dwarfed, finger-like hind wings (Baetis). . . . . . . . . . . . . . . . . . . . . . . . . Baetidae (in part)Hind wings not dwarfed, finger-like. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Hind wings large (1/2 size of front wings). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Hind wings medium sized, less than 1/2 size of front wings. . . . . . . . . . . . . . . . . . . . . . . . . 76. Dark forelegs, pale middle and rear legs. . . . . . . . . . . . . . . . . . . . Isonychiidae, Isonychia
All legs darker, conspicuous pattern of light and dark irregular bands on abdomen. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Siphlonuridae
7. Hind wings roundish, stout thorax with abdomen thick tapering dramatically from segments 6-10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Baetiscidae
Hind wings, thorax and abdomen not as above. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
8. Irregular hear-shaped band on femur (Epeorus). . . . . . . . . . . . . . (Heptageniidae, in part)
Femur without such a band. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
9. White wings (Ephoron, males). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Polymitarcyidae
Wings not white. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ameletidae
10. Dwarf hind wing (Callibaetis). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Baetidae (in part)
Hind wing various sizes, not dwarfed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
11. Dark band on femur (Maccaffertium, Stenonema, Stenacron). . . . . Heptageniidae (in part)
Femur without dark band, large mayfly (16-35 mm)(Hexagenia). . . . Ephemeridae (in part)
13. No hind wings, very small mayflies (2-6 mm). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Hind wings of various sizes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
14. (Trichoides). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Leptohyphidae (in part)
(Caenis, Sparbarus). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Caenidae
15. Small oval-like hind wings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Leptophlebiidae
Hind wings of various sizes, not small and oval. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
16. Wings white (Ephoron, females). . . . . . . . . . . . . . . . . . . . . . . . Polymitarcyidae (in part)
Wings, various colors, not white. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
17. Wings yellow (Anthopotamus). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Potamanthidae
Wings grayish or clear. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . 18
18. Middle tail shorter than side tails. . . . . . . . . . . . . . . . . . . . . . . Leptophlebiidae (in part)
Middle tail same length as side tails. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ephemerellidae
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Key to the Families of Ohio Mayfly Adults