Ephemeroptera Families

I. Ephemeroptera - Mayflies

A. Adults

• membranous wings with many veins
• wings held vertically at rest
• long cerci
• very short antennae
• 4 or 5 segmented tarsi
• mouthparts reduced
• hind wings much smaller than front or absent in a few

B. Nymphs

• 3 pairs of segmented thoracic legs
• distinct head
• 1 pair antennae
• no ventral styli or collophore and furcula
• aquatic
• compound eyes
• wings developing in fixed pads
• chewing mouthparts
• labium not extensible or folded back on itself
• tarsi with 1 claw
• abdomen ending in 3 long filaments, less commonly 2
• gills located on sides of abdomen; may be platelike, filamentous, or feathery

II. Adults

A. Family: Ephemeridae (Burrowing Mayflies)

1. Base of MP₂ bent in forewing toward CuA
2. Hind tarsi 4-segmented

B. Family: Heptageniidae (Flatheaded Mayflies)

1. Forewings with 2 pairs of cubital intercalaries, ICuA
2. Hind tarsi 5-segmented

C. Family: Baetidae (Small Minnow Mayflies)

1. Bases of MA₂ and MP₂ atrophied, and 1 or 2 short marginal veinlets between main longitudinal veins
2. Hind tarsi 3- or 4-segmented