Ephemeroptera

Definition

An order of aquatic insects within the subclass Palaeoptera, commonly known as mayflies. Adults are characterized by brief lifespans (typically 1–4 days), two or three long caudal filaments, and non-functional mouthparts; the subimago (preadult) stage is fully winged and capable of flight, a trait unique among extant insects. Nymphs are primarily aquatic, often serving as important bioindicators of water quality. The order comprises over 3,000 described species in 42 families worldwide.

Etymology

From Greek ephemeros (lasting a day) + pteron (wing), referring to the short adult lifespan.

Example

Baetis rhodani and Ephemera danica are common European Ephemeroptera used in biomonitoring of river health.

Synonyms

• Mayflies

Related Terms

• Palaeoptera
• subimago
• Imago
• Plecoptera
• Trichoptera
• aquatic insect
• bioindicator

Usage Notes

The order is sometimes grouped with Odonata (dragonflies and damselflies) in the paraphyletic or redefined clade Palaeoptera, characterized by wings that cannot be folded flat over the abdomen. The subimago stage is diagnostic: unlike all other living insects, mayflies molt once more after developing functional wings. In ecological contexts, 'Ephemeroptera' often appears alongside Plecoptera and Trichoptera (EPT) as sensitive indicators of clean, well-oxygenated freshwater.