Mayflies

Order: Ephemeroptera

Life Cycle• Hemimetabolous (egg, naiad, adult)

– Naiad: aquatic, gill-breathing nymph– Nymph: larva of an insect without a pupal stage

• 1-3 generations / year; 12-50 molts!• Subimago stage (“duns”)• Short-lived adult stage (“spinners”)

General Morphology

Naiads:Large eyesChewing mouthpartsGills on abdomenUsually 3 tails

Adults:Soft-bodiedFW large, triangular, veinedElongated forelegs, tails

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)

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

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!

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

Suborder Schistonota

SuperfamiliesBaetoidea (6 families)

Leptophlebioidea (1 family)

Ephemeroidea (5 families)

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.

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.

Metretopodidae(“Cleftfooted Minnow Mayflies”)

• Strong swimmers• Medium/large rivers• 2 claws on foreleg

Siphloplecton basale

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)

Baetidae

• Fall emergence in some species

• Note rounded 9th abdominal segment

Baetis longipalpus

(Antennae more than twice width of head)

Subimago Baetis tricaudatus

• Shorter front legs• Dull wings• Fringe of ciliated

hairs on wings• Dun, “little iron blue

quill”

Adult Baetis tricaudatus

• Longer front legs• Brighter colors• Spinner, “blue

winged olive (applies to Baetids in general)”

Oligoneuridae(“Brushlegged Mayflies”)

• Streamlined shape• Filter feed with hairs

on front legs• Swift currents

Isonychia sadleri

Isonychia Filter Feeding

Isonychia bicolor“Leadwing Coachman,”

“Mahogany Dun.”

Isonychia sadleri imago

Heptageniidae(Flatheaded Mayflies)

• Greatly flattened head, legs

• Clinging under rocks• Often very long tails

Stenonema rubrum

(Note unique 7th gill structure)

Heptageniidae(7th abdomimal gill)

S. rubrum

HeptageniidaeStenacron interpunctatum

• Subimago called “Light Cahill”

• 7-12 mm, excluding tails, legs

• May-September• Note relatively short

legs of subimago

Heptageniidae

S. Rubrum imago

Heptageniidae

• Cup-shaped to cling• Bright red gill color

Rhithrogena sanguinea

(Ventral view)

Superfamily Leptophlebioidea

Family

Leptophlebiidae (“Pronggills”)

Leptophlebiidae(“Pronggills”)

• Gills on segs. 1-6 or 1-7• Gills double or forked• Prefer crevices

Leptophlebia sp.

Leptophlebiidae

• Subimago called “dark blue quill”

• Small (6-8mm excluding tails, legs)

• August-October• Note long legs of

imagoParaleptophlebia debilis

imago

Superfamily Ephemeroidea

Families:

Behningidae (“Tuskless Burrowers”)*

Potatamanthidae (“Hacklegills”)

Polymitarcyidae (“Pale Burrowers”)

Ephemeridae (“Common Burrowers”)

Palingeniidae (“Spinyheaded Burrowers”)***Southeast U.S. only **South only

Potamanthidae(“Hacklegills”)

• Somewhat like Heptageniidae, but…

• Gills unique, laterally oriented

• Tusks, curve inward

Polymitarcyidae(“Pale Burrowers”)

• Larvae in silt, stream banks• Adult with nonworking legs• Sexually mature subimago• Subfamily id uses frontal

processes

Ephoron sp.

Polymitarcyinae

Campsurinae

Ephemeridae(“Common Burrowers”)

• Large, 12-32 mm• Tusks lack spines,

curve up & out• Burrow in silt-sand

in rivers or lakes

Ephemera sp.

Hexagenia sp.

Ephemera sp.

Hexagenia limbata(“Michigan Caddis”)

Ephemera guttulata subimago(“Green Drake”)

(18-21 mm + tails)

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

Suborder Pannota

Superfamilies

Ephemerelloidea (2 families)

Caenoidea (2 families)

Propistomatoidea (1 family)

Superfamily Ephemerelloidea

Families:

Ephemerellidae (“Spiny Crawlers”)

Tricorythidae (“Little Stout Crawlers”)

gills

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)

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

Superfamily Caenoidea

Families:

Neoephemeridae (“Large Squaregills”)

Caenidae (“Small Squaregills”)

Caenidae(“Small Squaregills”)

• Widespread and common in east

• Small, 3-4 mm + tails• No hind wing pads• Operculate gills

overlap slightly

Caenis simulans

Superfamily Propistomatoidea

Family

Baetiscidae (“Armored Mayflies”)

Baetiscidae(“Armored Mayflies”)

• Banks of medium streams

• Striking thoracic shield