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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 Neoleptophlebia (Leptophlebiidae) Mayfly Nymph from the Yakima River in Washington
Some characteristics from the microscope images for the tentative species id: The postero-lateral projections are found only on segment 9, not segment 8. Based on the key in Jacobus et al. (2014), it appears to key to Neoleptophlebia adoptiva or Neoleptophlebia heteronea, same as this specimen with pretty different abdominal markings. However, distinguishing between those calls for comparing the lengths of the second and third segment of the labial palp, and this one (like the other one) only seems to have two segments. So I'm stuck on them both. It's likely that the fact that they're immature nymphs stymies identification in some important way.
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 Iswaeon (Tiny Blue-Winged Olives)

This genus currently contains three species, only one of which is important to anglers. See Iswaeon anoka for details.

Where & when

In 10 records from GBIF, adults of this genus have been collected during July (40%), May (30%), June (20%), and September (10%).

In 4 records from GBIF, this genus has been collected at elevations of 3, 26, 886, and 1089 ft.

Genus Range

Start a Discussion of Iswaeon

References

Mayfly Genus Iswaeon (Tiny Blue-Winged Olives)

Taxonomy
1 species (Iswaeon davidi) isn't included.
Genus Range
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