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Flyfishing Entomology

Life Stage Characteristics

Ephemeroptera

 Larva

§        Abdomen ends with 3 (or 2) tails

§        Each leg ends with only a single claw

§        Gills are typically plate-like and located on sides of the abdomen

§        Instars: 15-25

Sub-Adult & Adult

§         Two or three long tails

§         Wings held vertically; front pair large and triangular; hind pair usually reduced, rarely absent

§         Body slender and delicate

Mayfly larvae (nymphs) can be readily identified by their (typically) plate-like gills located on the side of their abdomen and by their (2 or 3) slender tails.    They fall into one of four categories, depending on how they have evolved to survive in various habitats.

Mayflies are unique in having two winged life stages.  Both can be readily identified by their wings, which are held erect when at rest; by their jerky up-and-down flight when airborne; and by their ( 2 or 3) long slender tails.  The sub-adult (dun) has dull opaque wings, and the adult (spinner) has  hyaline (transparent and shiny) wings.  Wing venation characteristics can also be useful in the identification to family and genus.