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

Salmonflies
Pteronarcys californica

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

Stream photos

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Kogotus Stonefly Nymph Kogotus Stonefly Nymph

Dorsal view of a Kogotus (Perlodidae) Stonefly Nymph from Mystery Creek #199 in Washington

This one pretty clearly keys to Kogotus, but it also looks fairly different from specimens I caught in the same creek about a month later in the year. With only one species of the genus known in Washington, I'm not sure about the answer to this ID.

8 Recently Added Photos

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.

Troutnut is a project started in 2003 by salmonid ecologist Jason "Troutnut" Neuswanger to help anglers and fly tyers unabashedly embrace the entomological side of the sport. Learn more about Troutnut or support the project for an enhanced experience here.

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

source

Map of specific collection sites

Specimens of the Mayfly Genus Stenacron

1 Male Dun

Male Stenacron (Light Cahill) Mayfly Dun

13 Pictures

Artistic view of a Male Stenacron (Heptageniidae) (Light Cahill) Mayfly Dun from the Teal River in Wisconsin

Collected May 26, 2005 from the Teal River in Wisconsin

Added by Troutnut on May 22, 2006

Collected May 26, 2005 from the Teal River in Wisconsin and added by Troutnut on May 22, 2006

3 Female Duns

Female Stenacron interpunctatum (Light Cahill) Mayfly Dun

6 Pictures

Lateral view of a Female Stenacron interpunctatum (Heptageniidae) (Light Cahill) Mayfly Dun from the West Branch of Owego Creek in New York

This is a fairly small late-season female Stenacron dun.

Collected August 21, 2006 from the West Branch of Owego Creek in New York

Added by Troutnut on August 23, 2006

Collected August 21, 2006 from the West Branch of Owego Creek in New York and added by Troutnut on August 23, 2006

Female Stenacron (Light Cahill) Mayfly Dun

4 Pictures

Female Stenacron (Heptageniidae) (Light Cahill) Mayfly Dun from the Couderay River in Wisconsin

Collected July 13, 2004 from the Couderay River in Wisconsin

Added by Troutnut on January 25, 2006

Collected July 13, 2004 from the Couderay River in Wisconsin and added by Troutnut on January 25, 2006

Female Stenacron (Light Cahill) Mayfly Dun

3 Pictures

Female Stenacron (Heptageniidae) (Light Cahill) Mayfly Dun from unknown in Wisconsin

Collected July 30, 2004 from unknown in Wisconsin

Added by Troutnut on January 25, 2006

Collected July 30, 2004 from unknown in Wisconsin and added by Troutnut on January 25, 2006

1 Male Spinner

Male Stenacron interpunctatum (Light Cahill) Mayfly Spinner

8 Pictures

Lateral view of a Male Stenacron interpunctatum (Heptageniidae) (Light Cahill) Mayfly Spinner from the Namekagon River in Wisconsin

Collected June 9, 2005 from the Namekagon River in Wisconsin

Added by Troutnut on May 26, 2006

Collected June 9, 2005 from the Namekagon River in Wisconsin and added by Troutnut on May 26, 2006

1 Female Spinner

Female Stenacron (Light Cahill) Mayfly Spinner

4 Pictures

Lateral view of a Female Stenacron (Heptageniidae) (Light Cahill) Mayfly Spinner from the East Branch of the Delaware River in New York

Collected July 12, 2005 from the East Branch of the Delaware River in New York

Added by Troutnut on April 14, 2006

Collected July 12, 2005 from the East Branch of the Delaware River in New York and added by Troutnut on April 14, 2006

2 Nymphs

Stenacron interpunctatum (Light Cahill) Mayfly Nymph

6 Pictures

Dorsal view of a Stenacron interpunctatum (Heptageniidae) (Light Cahill) Mayfly Nymph from the Marengo River in Wisconsin

Collected June 4, 2005 from the Marengo River in Wisconsin

Added by Troutnut on May 25, 2006

Collected June 4, 2005 from the Marengo River in Wisconsin and added by Troutnut on May 25, 2006

Stenacron (Light Cahill) Mayfly Nymph

2 Pictures

Stenacron (Heptageniidae) (Light Cahill) Mayfly Nymph from unknown in Wisconsin

Collected August 7, 2004 from unknown in Wisconsin

Added by Troutnut on January 18, 2006

Collected August 7, 2004 from unknown in Wisconsin and added by Troutnut on January 18, 2006

1 Streamside Picture of Stenacron Mayflies:

View Fullsize

In this picture: Mayfly Species Stenacron interpunctatum (Light Cahill).

Taken November 29, 1999

Added by Troutnut on June 30, 2006

Taken November 29, 1999 and added by Troutnut on June 30, 2006

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

Start a Discussion of Stenacron

References

Fauceglia, Ted. 2005. Mayflies . Stackpole Books.
Knopp, Malcolm and Robert Cormier. 1997. Mayflies: An Angler's Study of Trout Water Ephemeroptera . The Lyons Press.