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Artistic view of a Male Pteronarcys californica (Pteronarcyidae) (Giant Salmonfly) Stonefly Adult from the Gallatin River in Montana
Pteronarcys californica

The giant Salmonflies of the Western mountains are legendary for their proclivity to elicit consistent dry-fly action and ferocious strikes.

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 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

8 replies
Posted by LittleJ on Nov 25, 2006
Last reply on Dec 1, 2006 by Troutnut
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.

Start a Discussion of Stenacron


Mayfly Genus Stenacron (Light Cahills)

Genus Range
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