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Hex (Hexagenia limbata)
Mayfly, hatching June–July, active in water between 60 and 72°F, and imitated at #6–8. Recorded from northern Wisconsin and the Wisconsin driftless, where 1611 Wisconsin rivers on this site carry a page.
A mayfly with a two-inch wingspan that hatches after dark on sand-bottomed rivers in the last weeks of June, peaking through June and July in water from 60 to 72 degrees — cold-transitional, cool and warm. It is the largest hatch on the northern Michigan calendar and the only one people schedule holidays around. The nymph burrows in soft silt and sand banks for two years, pale yellow and feathery-gilled, which is why a wiggle-nymph fished at dusk works before the hatch begins. The emerger swims up in near-darkness and the takes are heavy and unseen. The dun is enormous and pale yellow-cream, riding the surface in the dark and fished by ear. The spinner falls in the small hours, wings flat and body pale, often the heavier of the two events. Hook sizes are 6 and 8: Hex Dun and Hex Spinner at 6 to 8, Wiggle Hex Nymph at 6 to 8, Hex Nymph at 6 to 10.
- #6–8Hook size
- 60–72°FWater, active
- Jun–JulPeak months
- 4Life stages fished
What it is
Mayfly · Hexagenia limbata · nymph → emerger → dun → spinner
Hexagenia limbata: a mayfly with a two-inch wingspan that hatches after dark on sand-bottomed rivers in the last weeks of June. The single largest hatch on the northern Michigan calendar and the only one people schedule holidays around.
The biggest mayfly in the country and the reason people fish Michigan in the dark. Silt-bottom water, after sunset, by ear.
When it hatches
Peak is June–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 60°F to 72°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 | Burrows in soft silt and sand banks for two years. Pale yellow, feathery-gilled, and the reason a wiggle-nymph fished at dusk works before the hatch starts. |
| emerger | The nymph swims up in near-darkness. Takes are heavy and unseen. |
| dun | Enormous, pale yellow-cream, riding the surface in the dark. Fished by ear. |
| spinner | Falls in the small hours, wings flat, body pale. Often the heavier of the two events. |
Matching flies
4 patterns in this book imitate the Hex, 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.
- Hex Dun dry fly · #6–8 — Size 6 of pale yellow deer hair. You fish it by sound, not by sight.
- Hex Nymph nymph · #6–10 — Big burrower nymph. Worth dredging silt banks months either side of the hatch.
- Hex Spinner dry fly · #6–8 — The spent fall, later in the night than the dun and often better.
- Wiggle Hex Nymph nymph · #6–8 — Articulated burrowing-nymph imitation. Fished in the hour before the duns come off.
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.
- Adams Creek northern Wisconsin · July mean 66.2°F
- Alder Creek northern Wisconsin · July mean 65.8°F
- Arnold Creek northern Wisconsin · July mean 65.8°F
- Bacon Creek northern Wisconsin · July mean 65.8°F
- Badger Creek northern Wisconsin · July mean 65.8°F
- Barber Creek northern Wisconsin · July mean 65.8°F
- Bean Brook northern Wisconsin · July mean 65.8°F
- Bears Grass Creek northern Wisconsin · July mean 66.2°F
- Bearsdale Creek northern Wisconsin · July mean 65.8°F
- Beaver Brook northern Wisconsin · July mean 65.8°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
- northern Wisconsin WI
- the Wisconsin driftless WI
Rivers in these regions with a page here
- Saint Croix River
- Adams Creek
- Alder Creek
- Alder Creek
- Allen Creek
- Allen Creek
- Allen Creek
- Allen Creek
- Allenton Creek
- Allequash Creek
- Alvin Creek
- Amo Creek
- Anderson Creek
- Annis Creek
- Apple Branch
- Apple Creek
- Apple River
- Arkansaw Creek
- Armstrong Creek
- Armstrong Creek
- Arnold Creek
- Ash Creek
- Auburn Lake Creek
- Augustine Creek
- and 1587 more
Related hatches
Same family, or overlapping this one's calendar on the same water.
- Isonychia / Slate Drake Isonychia bicolor · Mayfly · June–September
- Light Cahill Maccaffertium ithaca · Mayfly · May–July
- Sulphur Ephemerella invaria · Mayfly · May–July
- Little Yellow May Leucrocuta / Heptagenia spp. · Mayfly · June–September
- Gray Drake Siphlonurus spp. · Mayfly · June–July