4. Mayflies Order: Ephemeroptera
Mayflies are the oldest of the winged insects to survive to the present day. The aquatic nyiads are quite different in appearance from the adults. Because many of the adults are extremely short-lived (ephemeral), they are given the order name, from the Greek ephemero, “lasting a day,” and pteron, “winged.”
Order: Ephemeroptera

5. Life Cycle Hemimetabolous (egg, naiad, adult)
Naiad: aquatic, gill-breathing nymph
Nymph: larva of an insect without a pupal stage
1-3 generations / year; molts!
Subimago stage (“duns”)
Short-lived adult stage (“spinners”)

6. General Morphology Naiads: Large eyes Chewing mouthparts
Gills on abdomen
Usually 3 tails
Adults:
Soft-bodied
FW large, triangular, veined
Elongated forelegs, tails

7. Naiad Morphology Well developed eyes Slender antennae
Well-developed legs, with one claw
Gills (abdomen sides)
Fore-wing pads may be present
Usually 3 caudal filaments (tails)

8. Adult Morphology Elongate, very soft FW large, many veins
HW small or absent
Wings above body at rest
Mouthparts vestigial
Fore-legs very long
2-3 long tails

9. Systematics
2 suborders: Schistonota (“Splitbacks”) and Pannota (“Fusedbacks”), refers to wing pads
3 superfamilies in each suborder
17 families
Characters used include gill structures, mouthparts, hairs/spination: these change with age!

10. Suborder Schistonota “Splitback Mayflies”
Larval fore wing pads free for at least half of the pad length
Thorax usually slim and delicate
Gill series usually well developed on sides of abdomen
Active and diverse mayflies

11. Suborder Schistonota Superfamilies Baetoidea (6 families)
Leptophlebioidea (1 family)
Ephemeroidea (5 families)

12. Superfamily Baetoidea
Families:
Siphlonuridae (“Primitive Minnow”)
Metretopodidae (“Cleftfooted Minnow”)
Ametropodidae (“Sand Minnow”)*
Baetidae (“Small Minnow”)
Oligoneuridae (“Brushlegged”)
Heptageniidae (“Flatheaded”)
* Western. 3 species, not covered here.

13. Siphloneuridae (“Primitive Minnow Mayflies”)
Streamlined
Long axis of head vertical
Fore legs w/o hairs
Platelike gills oriented dorsally
Sharp spines on posterior abd. Segments
Ameletus sp.

14. Metretopodidae (“Cleftfooted Minnow Mayflies”)
Strong swimmers
Medium/large rivers
2 claws on foreleg
Siphloplecton basale

15. Baetidae (“Small Minnow Mayflies”)
Small, 9-10 mm
Variety of habitats
Good swimmers
Some tolerate polluted water
Some with 2 tails!
Callibaetis (left)
Pseudocloeon (right)

16. Baetidae Fall emergence in some species
Note rounded 9th abdominal segment
Baetis longipalpus
(Antennae more than twice width of head)

17. Subimago Baetis tricaudatus
Shorter front legs
Dull wings
Fringe of ciliated hairs on wings
Dun, “little iron blue quill”

18. Adult Baetis tricaudatus
Longer front legs
Brighter colors
Spinner, “blue winged olive (applies to Baetids in general)”

19. Oligoneuridae (“Brushlegged Mayflies”)
Streamlined shape
Filter feed with hairs on front legs
Swift currents
Isonychia sadleri

20. Isonychia Filter Feeding

21. Isonychia bicolor “Leadwing Coachman,” “Mahogany Dun.”

22. Isonychia sadleri imago

23. Heptageniidae (Flatheaded Mayflies)
Greatly flattened head, legs
Clinging under rocks
Often very long tails
Stenonema rubrum
(Note unique 7th gill structure)

24. Heptageniidae (7th abdomimal gill)
S. rubrum

25. Heptageniidae Stenacron interpunctatum
Subimago called “Light Cahill”
7-12 mm, excluding tails, legs
May-September
Note relatively short legs of subimago

26. Heptageniidae
S. Rubrum imago

27. Heptageniidae Cup-shaped to cling Bright red gill color
Rhithrogena sanguinea
(Ventral view)

28. Superfamily Leptophlebioidea
Leptophlebiidae (“Pronggills”)

29. Leptophlebiidae (“Pronggills”)
Gills on segs. 1-6 or 1-7
Gills double or forked
Prefer crevices
Leptophlebia sp.

30. Leptophlebiidae Subimago called “dark blue quill”
Small (6-8mm excluding tails, legs)
August-October
Note long legs of imago
Paraleptophlebia debilis imago

31. Superfamily Ephemeroidea
Families:
Behningidae (“Tuskless Burrowers”)*
Potatamanthidae (“Hacklegills”)
Polymitarcyidae (“Pale Burrowers”)
Ephemeridae (“Common Burrowers”)
Palingeniidae (“Spinyheaded Burrowers”)**
*Southeast U.S. only **South only

32. Potamanthidae (“Hacklegills”)
Somewhat like Heptageniidae, but…
Gills unique, laterally oriented
Tusks, curve inward

33. Polymitarcyidae (“Pale Burrowers”)
Larvae in silt, stream banks
Adult with nonworking legs
Sexually mature subimago
Subfamily id uses frontal processes
Polymitarcyinae
Ephoron sp.
Campsurinae

34. Ephemeridae (“Common Burrowers”)
Ephemera sp.
Large, mm
Tusks lack spines, curve up & out
Burrow in silt-sand in rivers or lakes
Hexagenia sp.
Ephemera sp.

35. Hexagenia limbata (“Michigan Caddis”)

36. Ephemera guttulata subimago (“Green Drake”)
(18-21 mm + tails)

37. Suborder Pannota “Fusedback Mayflies”
Naiad with wing pad fused to thorax for at least half of pad length
Thorax robust
Gills lay on abdomen
Operculate (covering) gills

38. Suborder Pannota Superfamilies Ephemerelloidea (2 families)
Caenoidea (2 families)
Propistomatoidea (1 family)

39. Superfamily Ephemerelloidea
Families:
Ephemerellidae (“Spiny Crawlers”)
Tricorythidae (“Little Stout Crawlers”)
gills

40. Ephemerellidae (“Spiny Crawlers”)
5-15 mm + tails
dorsal spines on head, thorax, abdomen
No gills on segment 2
Gills lie on abdomen
Serratella sp. (left)
Timpanoga sp. (right)

41. Tricorythidae (“Stout Little Crawlers”)
3-10 mm + tails
Hind wing pad absent or minute
Gills on seg. 2-6
Gills on 2 are triangular and operculate

42. Superfamily Caenoidea
Families:
Neoephemeridae (“Large Squaregills”)
Caenidae (“Small Squaregills”)

43. Caenidae (“Small Squaregills”)
Widespread and common in east
Small, 3-4 mm + tails
No hind wing pads
Operculate gills overlap slightly
Caenis simulans

44. Superfamily Propistomatoidea
Baetiscidae (“Armored Mayflies”)

45. Baetiscidae (“Armored Mayflies”)
Banks of medium streams
Striking thoracic shield