Little Sulphur (Ephemerella dorothea)

Mayfly, hatching May–July, active in water between 50 and 62°F, and imitated at #16–20. Recorded from 6 of the 8 regions this map covers, across Michigan, Wisconsin, Virginia, North Carolina and Minnesota.

#16–20Hook size
50–62°FWater, active
May–JulPeak months
4Life stages fished

Subbasins with trout water where it is on record: 80 of 326 across the 6 states this map draws.

See the trout water on the live map → Every reach coloured by water temperature — the water these hatches come off.

What it is

Mayfly · Ephemerella dorothea · nymph → emerger → dun → spinner

A small pale mayfly, sulphur-yellow body washed with orange, pale dun wings and three tails. Distinctly smaller than the E. invaria sulphurs that precede it — a #18 where those are a #14.

The smaller, later half of what everyone calls 'the sulphur'. Where E. invaria comes off in the afternoon at a #14, dorothea comes off at dusk two or three sizes down, and a refusal in June is usually a size problem rather than a pattern one.

When it hatches

The months below are this site's shared calendar, which covers 6 regions at once. In southeast Minnesota the state's own source says June, and the Minnesota page is built on that instead.

Peak is May–July. The pale months either side are the shoulder — the app widens a peak by one month in each direction and recommends the bug there, and no further: that widening is bounded so that a bug peaking in May is never offered in August.

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peak shoulder not recommended

Water conditions

The band is a water temperature, not an air temperature, and it is the range in which this insect is worth fishing — for a mayfly that is the emergence window; for a scud or a midge it is simply the range trout will still eat one in.

50°F 62°F

Active from 50°F to 62°F. On this map that is cold, cold-transitional water — the band crosses 1 of the three break the river colours use. Breaks at 58, 64 and 70°F.

Stages

What the insect is doing, and what that means for what you tie on.

Stage	What it is
nymph	A stout crawler in gravel and among weed, dark olive-brown. Available for months before the hatch and worth fishing as a dropper all spring.
emerger	Emergence is at dusk and in the film. The stuck-in-the-shuck stage is where most of the eating happens, and a low-riding comparadun is usually the difference between refusals and takes.
dun	Pale yellow, upright-winged, on the water in the last half-hour of light. It rides briefly in warm weather and much longer in cool.
spinner	Falls after dark, often over the same water an hour after the hatch. A rusty spinner fished blind into the sound of rises is the standard way to fish it.

Matching flies

5 patterns in this book imitate the Little Sulphur, across its stages. Which one to tie on follows the stage the water temperature says it is in — the app makes that call on a live reading; this page lists the whole set.

Where to find it right now

The rivers with a page here that sit in this insect's regions, with a USGS gauge reporting water temperature. This list is re-ranked against the reading each gauge is sending now and today's date, so it is live — the fallback below it, if the readings do not arrive, is each river's measured July mean.

Regional presence

Regions, not collection records. This insect is recorded from the coarse regions below; nobody has surveyed which named river it has been caught on, and this page will not pretend otherwise.

northern lower Michigan MI
southern lower Michigan MI
the Wisconsin driftless WI
the Virginia mountains VA
the North Carolina mountains NC
southeast Minnesota MN

Rivers in these regions with a page here

Related hatches

Same family, or overlapping this one's calendar on the same water.

Open the trout map →Every trout stream near you, coloured by today's water temperature.