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Sulphur (Ephemerella invaria)
Mayfly, hatching May–July, active in water between 52 and 68°F, and imitated at #14–18. Recorded from the Virginia mountains, where 796 Virginia rivers on this site carry a page.
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A pale yellow to yellow-orange mayfly, size 14 to 18, whose evening emergences run for weeks in late spring and early summer, peaking through May, June and July. It is the most dependable evening hatch on much of this water. The nymph is a small olive-brown crawler in gravel and weed. Emergence comes in the last hour of light, with the insects stalling in the film, and trout working a sulphur emergence key on the shuck rather than the fly riding above it. The dun is pale sulphur-yellow with a faint orange cast and upright pale-grey wings. The spinner fall follows the emergence, sometimes in complete darkness, rusty-orange bodied with clear spent wings, and is often better than the dun. Activity spans 52 to 68 degrees, covering cold, cold-transitional and cool water. Frenchie 12 to 18, Pheasant Tail 12 to 22, Sulphur Comparadun 14 to 20, Sulphur Dun and PMD Sparkle Dun 14 to 18, Rusty Spinner 14 to 20, Parachute Adams 12 to 20.
- #14–18Hook size
- 52–68°FWater, active
- May–JulPeak months
- 4Life stages fished
What it is
Mayfly · Ephemerella invaria · nymph → emerger → dun → spinner
A pale yellow to yellow-orange mayfly, size 14 to 18, whose evening emergences run for weeks in late spring and early summer. The most dependable evening hatch on much of this water.
Evening hatch. The spinner fall after dark is often better than the dun.
When it hatches
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.
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.
Active from 52°F to 68°F. On this map that is cold, cold-transitional, cool water — the band crosses 2 of the three breaks 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 small olive-brown crawler, common in gravel and weed. |
| emerger | Sulphurs emerge in the last hour of light and stall in the film. Trout on a sulphur emergence key on the shuck. |
| dun | Pale sulphur-yellow with a faint orange cast, upright pale-grey wings. |
| spinner | The fall comes after the emergence, sometimes in complete darkness, with rusty-orange bodies and clear spent wings. |
Matching flies
7 patterns in this book imitate the 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.
- Frenchie nymph · #12–18 — A Pheasant Tail with a hot spot. The most-fished competition nymph there is.
- Parachute Adams dry fly · #12–20 — Universal mayfly dun imitation. Every angler carries these.
- Pheasant Tail Nymph nymph · #12–22 — The mayfly nymph. Beadhead or not, size 16, and half the trout in the world have eaten one.
- PMD Sparkle Dun dry fly · #14–18 — Morning fly on spring creeks. Trailing shuck does most of the work.
- Rusty Spinner dry fly · #14–20 — Almost every mayfly spinner is rust-coloured. This covers the last hour of light.
- Sulphur Comparadun emerger · #14–20 — No hackle, sits in the film. What to tie on when duns are drifting past untouched.
- Sulphur Dun dry fly · #14–18 — Pale yellow-orange. Evening hatch fly on nearly every eastern river.
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.
- Cascades Creek the Virginia mountains · July mean 59.2°F
- Left Prong Wilson Creek the Virginia mountains · July mean 59.2°F
- Lick Block Run the Virginia mountains · July mean 59.2°F
- Falling Spring Creek the Virginia mountains · July mean 63.1°F
- Indiandraft Creek the Virginia mountains · July mean 63.1°F
- Jerrys Run the Virginia mountains · July mean 63.1°F
- Camp Branch the Virginia mountains · July mean 56.0°F
- Jackson River the Virginia mountains · July mean 66.3°F
- Biggs Run the Virginia mountains · July mean 67.5°F
- Furnace Branch the Virginia mountains · July mean 67.5°F
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 Upper Peninsula MI
- the Wisconsin driftless WI
- northern Wisconsin WI
- the Virginia mountains VA
- the North Carolina mountains NC
- southeast Minnesota MN
Rivers in these regions with a page here
- Jackson River
- Smith River
- Als Run
- Alum Creek
- Amos Branch
- Anderson Run
- Ararat River
- Auberry Creek
- Back Creek
- Back Creek
- Back Fork
- Back Run
- Baker Branch
- Baldwin Branch
- Baldwin Branch
- Barbours Creek
- Bark Camp Branch
- Bark Camp Branch
- Barkcamp Branch
- Barnard Creek
- Barney Run
- Barterbrook Branch
- Batie Creek
- Battery Creek
- and 772 more
Related hatches
Same family, or overlapping this one's calendar on the same water.
- Light Cahill Maccaffertium ithaca · Mayfly · May–July
- Little Sulphur Ephemerella dorothea · Mayfly · May–July
- Isonychia / Slate Drake Isonychia bicolor · Mayfly · June–September
- Little Yellow May Leucrocuta / Heptagenia spp. · Mayfly · June–September
- March Brown Maccaffertium vicarium · Mayfly · May–June