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Little Yellow May (Leucrocuta / Heptagenia spp.)
Mayfly, hatching June–September, active in water between 58 and 70°F, and imitated at #16–18. Recorded from northern lower Michigan and the Upper Peninsula, where 985 Michigan rivers on this site carry a page.
- #16–18Hook size
- 58–70°FWater, active
- Jun–SepPeak months
- 4Life stages fished
What it is
Mayfly · Leucrocuta / Heptagenia spp. · nymph → emerger → dun → spinner
A small bright yellow mayfly, upright wings, two tails, on a flattened clinger nymph. In flight it is easy to mistake for a Little Yellow Sally; on the water the upright wings and tails settle it.
A small bright-yellow clinger mayfly that trickles off through the back half of summer on mountain freestone. Easy to mistake for a Little Yellow Sally in the air; the mayfly has upright wings and two tails, the stonefly neither.
When it hatches
Peak is June–September. 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 58°F to 70°F. On this map that is cold-transitional, cool, warm 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 flat clinger on rock in riffle and pocket water, dark and mottled and nothing like the yellow adult. |
| emerger | In the film through the afternoon and evening, generally as a trickle rather than a hatch. |
| dun | Bright yellow and small, coming off across the back half of summer. Its usefulness is precisely that it is around when nothing else is. |
| spinner | Evening falls, often mixed with sulphurs and cahills of the same size. |
Matching flies
4 patterns in this book imitate the Little Yellow May, 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.
- Cahill Comparadun emerger · #14–18 — No hackle, deer-hair wing, body in the film. What to change to when the fish start refusing the standing dun.
- Pheasant Tail Nymph nymph · #12–22 — The mayfly nymph. Beadhead or not, size 16, and half the trout in the world have eaten one.
- Rusty Spinner dry fly · #14–20 — Almost every mayfly spinner is rust-coloured. This covers the last hour of light.
- 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.
- Barger Creek northern lower Michigan · July mean 65.5°F
- Barker Creek northern lower Michigan · July mean 65.5°F
- Chub Creek northern lower Michigan · July mean 65.5°F
- Crapo Creek northern lower Michigan · July mean 65.5°F
- East Branch Au Sable River northern lower Michigan · July mean 65.5°F
- East Branch Big Creek northern lower Michigan · July mean 65.5°F
- Haymeadow Creek northern lower Michigan · July mean 65.5°F
- Middle Branch Big Creek northern lower Michigan · July mean 65.5°F
- North Branch Au Sable River northern lower Michigan · July mean 65.5°F
- Rattlesnake Creek northern lower Michigan · July mean 65.5°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
- the Upper Peninsula MI
- the Wisconsin driftless WI
- northern Wisconsin WI
- the Virginia mountains VA
- the North Carolina mountains NC
Rivers in these regions with a page here
- Au Sable River
- Muskegon River
- Escanaba River
- Abitosse Creek
- Acme Creek
- Adams Creek
- Addis Creek
- Adventure Creek
- Aho Creek
- Ahola Creek
- Alabaster Whitney Drain
- Aldridge Creek
- Allen Creek
- Alward Creek
- Amundsan Creek
- Anderson Bayou
- Anderson Creek
- Anna River
- Antler Creek
- Antrim Creek
- Apple Creek
- Arsenault Creek
- Asum Creek
- Atkinson Creek
- and 961 more
Related hatches
Same family, or overlapping this one's calendar on the same water.
- Isonychia / Slate Drake Isonychia bicolor · Mayfly · June–September
- Trico Tricorythodes spp. · Mayfly · July–September
- Yellow Drake Ephemera varia · Mayfly · June–August
- Light Cahill Maccaffertium ithaca · Mayfly · May–July
- Sulphur Ephemerella invaria · Mayfly · May–July