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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 Skwala (Perlodidae) (Large Springfly) Stonefly Nymph from the Yakima River in Washington
This Skwala nymph still has a couple months left to go before hatching, but it's still a good representative of its species, which was extremely abundant in my sample for a stonefly of this size. It's obvious why the Yakima is known for its Skwala hatch.
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 Stenacron (Light Cahills)

The species in this genus were formerly classified in Stenonema. See the genus Maccaffertium for details. Only one species, Stenacron interpunctatum, is important to fly fishermen. See its page for details.

Where & when

In 197 records from GBIF, adults of this genus have mostly been collected during June (28%), July (23%), May (19%), and August (17%).

In 143 records from GBIF, this genus has been collected at elevations ranging from 3 to 9236 ft, with an average (median) of 2707 ft.

Genus Range

Specimens of the Mayfly Genus Stenacron

1 Male Dun
3 Female Duns
1 Male Spinner
1 Female Spinner
2 Nymphs

1 Streamside Picture of Stenacron Mayflies:

Discussions of Stenacron

cahills
8 replies
Posted by LittleJ on Nov 25, 2006
Last reply on Dec 1, 2006 by Troutnut
Jason
I know I'm a little out of season, butI was curious if you had any shots of Stenacron Interpunctatum next to your hook quide, or could just give me a size range. I was thinking they were 14-16 but could be wrong. Also you have written that Stenacron Interpunctatum were rarely called cahills. If so what mayfly is it that i'm after (that is common name "cahill"). The stenacron look the same to me, but i have also never kept and memorized any specimens.
Thanks
Jeff

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References

Mayfly Genus Stenacron (Light Cahills)

Genus Range
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