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Yellow Mays

Like most common names, "Yellow May" can refer to more than one taxon. They're previewed below, along with 9 specimens. For more detail click through to the scientific names.

Mayfly Species Stenacron interpunctatum

These are very rarely called Yellow Mays.
This is the best of the sporadic summer hatches known to anglers as Light Cahills. It was formerly known as Stenonema canadense and is considered by most angling historians as the model for that classic Catskill pattern.
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
Female Stenacron interpunctatum (Light Cahill) Mayfly DunFemale Stenacron interpunctatum (Light Cahill) Mayfly Dun View 6 PicturesThis is a fairly small late-season female Stenacron dun.
Collected August 22, 2006 from in
Added to Troutnut.com by on August 23, 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 Ephemerella invaria

These are very rarely called Yellow Mays.
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 7 Pictures
Collected May 26, 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

Mayfly Species Ephemera varia

These are very rarely called Yellow Mays.
This is an excellent hatch of a different character than its Ephemera brethren. Rather than emerging in a flurry of activity within a week, the Ephemera varia flies may last for more than a month in a single place.
Ephemera varia (Yellow Drake) Mayfly NymphEphemera varia (Yellow Drake) Mayfly Nymph View 4 Pictures
Collected March 29, 2006 from in
Added to Troutnut.com by on April 6, 2006
Female Ephemera varia (Yellow Drake) Mayfly DunFemale Ephemera varia (Yellow Drake) Mayfly Dun View 7 PicturesThis yellow drake dun hatched out of my aquarium over a month before her brethren in the wild are slated to emerge. She seems a bit small, and that might be the reason.
Collected May 13, 2007 from in
Added to Troutnut.com by on May 18, 2007
Female Ephemera varia (Yellow Drake) Mayfly SpinnerFemale Ephemera varia (Yellow Drake) Mayfly Spinner View 6 PicturesI found this female spinner ovipositing in a small stream. She came along while I was playing a trout -- every good bug seemed to do that last night! I didn't have my bug net, so I caught the trout in my landing net, released the trout, and caught the mayfly in my landing net. Her wing got a bit messed up from that.
Collected July 7, 2006 from in
Added to Troutnut.com by on July 8, 2006
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