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Light Cahills

Like most common names, "Light Cahill" can refer to more than one taxon. They're previewed below, along with 11 specimens. For more detail click through to the scientific names.

Mayfly Genus Stenacron

These are pretty much always called 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.
Stenacron interpunctatum (Light Cahill) Mayfly NymphStenacron interpunctatum (Light Cahill) Mayfly Nymph View 7 Pictures
Collected June 5, 2005 from in
Added to Troutnut.com by on May 25, 2006
Male Stenacron (Light Cahills) Mayfly DunMale Stenacron (Light Cahills) Mayfly Dun View 13 Pictures
Collected May 27, 2005 from in
Added to Troutnut.com by on May 22, 2006
Male Stenacron interpunctatum (Light Cahill) Mayfly SpinnerMale Stenacron interpunctatum (Light Cahill) Mayfly Spinner View 8 Pictures
Collected June 10, 2005 from in
Added to Troutnut.com by on May 26, 2006

Mayfly Species Maccaffertium ithaca

These are often called Light Cahills.
Maccaffertium ithaca (Light Cahill) Mayfly NymphMaccaffertium ithaca (Light Cahill) Mayfly Nymph View 9 PicturesThis specimen seems to be of the same species as a dun I photographed which emerged from another nymph in the same sample.
Collected May 29, 2007 from in
Added to Troutnut.com by on June 4, 2007
Female Maccaffertium ithaca (Light Cahill) Mayfly DunFemale Maccaffertium ithaca (Light Cahill) Mayfly Dun View 10 PicturesThis female looks very much like a male I collected a few hundred miles away a few days later, so I'm guessing it's the same species, which I believe is Maccaffertium mediopunctatum.
Collected May 23, 2007 from in
Added to Troutnut.com by on June 4, 2007

Mayfly Species Maccaffertium pulchellum

These are often called Light Cahills.

Mayfly Species Cinygma dimicki

These are sometimes called Light Cahills.

Mayfly Species Epeorus vitreus

These are sometimes called Light Cahills.
This is the second most common Epeorus species in the East and Midwest. Most anglers will encounter sporadic hatches of Epeorus vitreus once in a while, and sometimes a more concentrated emergence causes a good rise of fish.
Epeorus vitreus (Sulphur) Mayfly NymphEpeorus vitreus (Sulphur) Mayfly Nymph View 6 Pictures
Collected February 7, 2004 from in
Added to Troutnut.com by on January 25, 2006
Female Epeorus vitreus (Sulphur) Mayfly DunFemale Epeorus vitreus (Sulphur) Mayfly Dun View 6 Pictures
Collected May 28, 2005 from in
Added to Troutnut.com by on May 24, 2006
Female Epeorus vitreus (Sulphur) Mayfly SpinnerFemale Epeorus vitreus (Sulphur) Mayfly Spinner View 9 Pictures
Collected September 19, 2006 from in
Added to Troutnut.com by on October 4, 2006

Mayfly Species Ephemerella invaria

These are very rarely called Light Cahills.
This species, the primary "Sulphur" hatch, stirs many feelings in the angler. There is nostalgia for days when everything clicked and large, selective trout were brought to hand. There is the bewildering memory of towering clouds of spinners which promise great fishing and then vanish back into the aspens as night falls. There is frustration from the maddening selectivity with which trout approach the emerging duns--a vexing challenge that, for some of us, is the source of our excitement when Sulphur time rolls around.

Ephemerella invaria is one of the two species frequently known as Sulphurs (the other is Ephemerella dorothea). There used to be a third, Ephemerella rotunda, but entomologists recently discovered that invaria and rotunda are a single species with an incredible range of individual variation. This variation and the similarity to the also variable dorothea make telling them apart exceptionally tricky.

As the combination of two already prolific species, this has become the most abundant of all mayfly species in Eastern and Midwestern trout streams.
Ephemerella invaria (Sulphur Dun) Mayfly NymphEphemerella invaria (Sulphur Dun) Mayfly Nymph View 8 PicturesThis small Ephemerella invaria nymph was at least a month away from emergence.
Collected April 19, 2006 from in
Added to Troutnut.com by on April 21, 2006
Male Ephemerella invaria (Sulphur Dun) Mayfly DunMale Ephemerella invaria (Sulphur Dun) Mayfly Dun View 6 Pictures
Collected May 25, 2007 from in
Added to Troutnut.com by on June 4, 2007
Male Ephemerella invaria (Sulphur Dun) Mayfly SpinnerMale Ephemerella invaria (Sulphur Dun) Mayfly Spinner View 12 Pictures
Collected June 3, 2005 from in
Added to Troutnut.com by on May 24, 2006
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