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Lateral view of a Female Hexagenia limbata (Ephemeridae) (Hex) Mayfly Dun from the Namekagon River in Wisconsin
Hex Mayflies
Hexagenia limbata

The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.

Dorsal view of a Epeorus albertae (Heptageniidae) (Pink Lady) Mayfly Nymph from the East Fork Issaquah Creek in Washington
This specimen keys to the Epeorus albertae group of species. Of the five species in that group, the two known in Washington state are Epeorus albertae and Epeorus dulciana. Of the two, albertae has been collected in vastly more locations in Washington than dulciana, suggesting it is far more common. On that basis alone I'm tentatively putting this nymph in albertae, with the large caveat that there's no real information to rule out dulciana.
27" brown trout, my largest ever. It was the sub-dominant fish in its pool. After this, I hooked the bigger one, but I couldn't land it.
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Mayfly Genus Attenella

This genus is represented by several important species across the country. In the East, Attenella attenuata (Little Blue-winged Olive) has garnered much attention as an important hatch in past angling texts. However, possible confusion with more abundant Drunella species of Blue-winged Olives has perhaps led to overstatement regarding its importance.

The species Attenella margarita (Little Western Blue-winged Olive) is disributed nationally. Though its eastern presence is relatively minor, in the West this mayfly can produce exceptional hatches.

Two other western species, Attenella delantala and to a lesser extent Attenella soquele often show up quite prominently in stream samples taken in the coastal states. The dramatically marked delantala nymph cannot be easily confused with any other western ephemerellid. Information regarding their winged appearance seems to be unavailable for now. Why they have gone unreported in angling texts is a mystery perhaps due to emergence behavior or misidentification by anglers of the dun and spinner stages. There is much to learn about these species that can be fairly abundant in some locales.

Where & when

In 18 records from GBIF, adults of this genus have been collected during July (56%), June (17%), August (17%), May (6%), and April (6%).

In 6 records from GBIF, this genus has been collected at elevations ranging from 194 to 8350 ft, with an average (median) of 5420 ft.

Genus Range

Hatching behavior

A significant difference between this genus and other ephemerellids is it's reported propensity to emerge from its nymphal shuck from the stream bottom in heptagenid fashion. While other ephemerellids can and do emerge underwater, this usually takes place within a foot at most from the surface. Attenella's availability as a submerged dun in the entire water column means use of the winged wetfly or soft hackles fished deeply can be an important tactic.

Specimens of the Mayfly Genus Attenella

1 Male Dun
3 Female Duns
3 Nymphs

Start a Discussion of Attenella

References

Mayfly Genus Attenella

Genus Range
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