Sulphur Mayfly Hatch
invaria & Ephemerella dorothea
The Sulphur mayfly hatch offers Wisconsin fly fishermen a great
opportunity to fly fish for rising trout feeding on these prolific mayfly hatches. The "sulphurs" is a common term used to describe two of the Ephemerella mayfly species
that hatch on many Wisconsin trout streams from mid-May through mid-June, depending on the stream.
The far northern Wisconsin streams may not see the suplhurs until the end of
May or early June. While soutwestern and central Wisconsin streams may start
see see sulphurs hatching by mid-May.
The mayflies that we generally referred too as "sulphurs" in Wisconsin
are Ephemerella invaria, Ephemerella excrucians and
the Ephemerella dorothea.
These mayfly species are extremely abundant on many Wisconsin trout streams and can produce
very dense hatches and spinner falls. The sulphurs follow the Hendricksons,
which is also part of the Ephemerella genus, and have very similar traits.
(Including, the duns have 3 tails.) They are found living in the same type
of waters. The biggest difference the sulphurs versus the Hendricksons is the
sulphurs will generally hatch late afternoon to evening, depending on water
temperatures and surrounding conditions.
Sizes range from #14 to #18, with Ephemerella dorothea being
smaller in size and more pale yellow than Ephemerella invaria and Ephemerella excrucians mayflies.
It is advisable to carry nymphs, emergers and duns in all those sizes (#14
- #18). Colors may vary slightly depending on the stream. Pheasant tail nymphs,
hare's ears, or wiggle nymphs are great sulphur nymph imitations. Look for
the nymphs in the riffled waters, especially where the bottom is mainly small
gravel and rock. Emergers and comparaduns make a great choice when the sulphurs
are hatching on the water. Sulphur male duns have larger eyes and are darker in color,
while the females are generally lighter and more of a pale yellow. The
spinner falls occur at dusk with the females dropping their eggs into the water
from above in the air. Fly fishing during the spinner falls is real spotty
because the mayfiles spinners may take hours to fall spent on the water.
Click on a sulphur mayfly patterns below for a larger view
Sulphur Dun Pattern
** Click here for Sulphur Comparadun pattern and some additional tying details
Hatch Reviewed: Mayflies: Sulphur Mayfly Hatch
By: John Simonson
Hatch Rating: 4.5
Date: 23 May 2009
The sulphur mayfly hatch is a major Wisconsin hatch and
this page gives you a general overview about this mayfly hatch.