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Hendrickson (Ephemerella subvaria)
Mayfly, hatching April–May, active in water between 45 and 58°F, and imitated at #12–14. Recorded from the Wisconsin driftless and northern Wisconsin, where 1611 Wisconsin rivers on this site carry a page.
The first hatch of the year worth planning a trip around, peaking in April and May in water from 45 to 58 degrees — cold and cold-transitional only — and coming off in the early afternoon when the water is warmest. The nymph is a stout, three-tailed crawler clinging to gravel and cobble in moderate current, available all winter; a dark hare's-ear or pheasant-tail on the bottom is a Hendrickson nymph whether anyone calls it one or not. Emergence is slow and happens in the film, and trout key on it hard enough that a floating dun over feeding fish is frequently refused while a film pattern is not. The dun has upright grey wings over a tan-pink body and rides for several yards before flying. Females are paler and larger than the dark males, which anglers once treated as a separate hatch, the Red Quill. Evening spinners darken to rust-brown, so a Red Quill Spinner at 12 to 16 covers the fall and a dun pattern, size 12 to 14, does not.
- #12–14Hook size
- 45–58°FWater, active
- Apr–MayPeak months
- 4Life stages fished
What it is
Mayfly · Ephemerella subvaria · nymph → emerger → dun → spinner
A medium mayfly with a pinkish-tan body and slate-grey wings that stand upright over the water like small sails. The female is noticeably paler and larger than the male, which is dark enough that anglers once treated the two as separate hatches — the Hendrickson and the Red Quill.
The first hatch of the year worth planning a trip around. Comes off early afternoon, when the water is warmest.
When it hatches
Peak is April–May. 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 45°F to 58°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, three-tailed crawler that clings to gravel and cobble in moderate current. It is available all winter, and a dark hare's-ear or pheasant-tail fished on the bottom is a Hendrickson nymph whether anyone calls it one or not. |
| emerger | Emergence happens in the film, and it is slow: the dun struggles out of the nymphal shuck at the surface and drifts. Trout key on this stage hard enough that a floating dun over feeding fish is frequently refused while a film pattern is not. |
| dun | Upright grey wings, tan-pink body, riding the surface for several yards before flying. This is the stage the hatch is named for and the one worth planning an afternoon around. |
| spinner | The mated female returns in the evening with clear wings held flat on the water. Bodies darken to rust-brown, which is why a Red Quill Spinner covers the fall and a dun pattern does not. |
Matching flies
5 patterns in this book imitate the Hendrickson, 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.
- Hare's Ear Nymph nymph · #10–18 — Looks like everything and nothing. The other half of a two-nymph rig.
- Hendrickson Dun dry fly · #12–14 — Pink-grey body, dun hackle. Matched to the real thing when a general pattern gets refused.
- 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.
- Red Quill Spinner dry fly · #12–16 — The Hendrickson male, and the evening fall after the hatch.
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.
- Basteen Creek northern Wisconsin
- Beaver Creek northern Wisconsin
- Blake Creek northern Wisconsin
- Bonita Creek northern Wisconsin
- Casco Creek northern Wisconsin
- Chickney Creek northern Wisconsin
- Cunningham Creek northern Wisconsin
- Devils River northern Wisconsin
- East Twin River northern Wisconsin
- Embarrass River northern Wisconsin
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
- 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.
- Blue-Winged Olive Baetis spp. · Mayfly · March–May and September–November
- Blue Quill Paraleptophlebia adoptiva · Mayfly · April–May
- Light Cahill Maccaffertium ithaca · Mayfly · May–July
- Sulphur Ephemerella invaria · Mayfly · May–July
- Little Sulphur Ephemerella dorothea · Mayfly · May–July