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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 eyes Chewing mouthparts Gills on abdomen Usually 3 tails Adults: Soft-bodied FW large, triangular, veined Elongated 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 Superfamilies Baetoidea (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

Heptageniidae Stenacron 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

(Ventral view)

Rhithrogena sanguinea

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 imago

Paraleptophlebia 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

Polymitarcyinae

Ephoron sp. Campsurinae

Ephemeridae (“Common Burrowers”) • Large, 12-32 mm • Tusks lack spines, curve up & out • Burrow in silt-sand in rivers or lakes

Ephemera sp.

Ephemera sp.

Hexagenia 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