Like most common names, "Sulphur Dun" can refer to more than one taxon. They're previewed below, along with 5 specimens. For more detail click through to the scientific names.
These are pretty much always called Sulphur Duns.
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.
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
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.
These are often called Sulphur Duns.