Mayfly · Ephemerella excrucians and relatives
Pale Morning Dun
Also called PMD, Ephemerella.
Short answer
The pale morning dun is a pale yellow-olive mayfly, hook size 14 to 18, that hatches through the middle of the day in early and midsummer. It is the defining western summer hatch, it lasts for weeks rather than days, and trout become extremely selective to it because it is so reliable.
What a pale morning dun is
The pale morning dun is the western angler's summer mayfly: a medium-small insect with a pale yellow to pale olive body and light dun wings, hatching from late morning into the afternoon from roughly June into August. It is the hatch that rewards patience, because unlike the explosive one-week drakes the PMD runs for weeks on the same river, and trout that see it every day for a month stop making mistakes. The females vary noticeably in colour even on one river — some distinctly yellow, some closer to pink-orange — which is why anglers carry three shades and still get refused.
- Hook size
- Hook sizes 14 to 18, most often 16
- Colour
- Pale yellow to pale olive body, sometimes pinkish; light grey wings; three tails
The stages trout eat
- Nymph
- A squat, dark crawler nymph. Effective for days before the hatch starts and in the hours before it each morning.
- Emerger
- PMDs are notoriously slow to leave the shuck, and trout exploit it. A cripple or stuck-shuck pattern is often the answer.
- Dun
- Pale, upright-winged and conspicuous on the water. The stage everyone fishes and the one fish most often refuse.
- Spinner
- Rusty-bodied and spent-winged, falling in the evening. A rusty spinner fall can be the best hour of the day.
When does the pale morning dun hatch?
| When | What is happening |
|---|---|
| Late May – June | The hatch begins on the warmer rivers. Late morning starts, and fish that have not seen a dry fly all year. |
| July | Peak. Daily midday hatches, spinner falls in the evening, and increasingly selective trout. |
| August | Tapering. Hatches start earlier in the morning as the days warm, and the fish are now thoroughly educated. |
| September | Scattered late emergences on cooler rivers, overlapping with the autumn Baetis. |
Emergence dates move with latitude, altitude and the weather of a given year. Treat these windows as a shape, not a diary, and check a local report before you travel.
Where it matters
Western rivers above all: Montana, Idaho, Wyoming, Colorado and the Utah tailwaters. The Henry's Fork and the Missouri below Holter are famous for how difficult their PMD fishing is. Eastern anglers meet the closely related sulphurs, which behave much the same way.
Fly fishing in Montana Fly fishing in Idaho Fly fishing in Wyoming Fly fishing in Colorado Fly fishing in Utah
How to fish it
Expect refusals and plan for them. Carry the dun, a cripple and a rusty spinner, and change stage before you change size. A dead drift matters more here than anywhere — these fish get a long look in flat water. If the fish are rising steadily and ignoring everything, watch what they are actually doing: a nose that barely breaks the surface is eating emergers, not duns.
- Carry three body shades. PMDs vary river to river and even morning to afternoon.
- The spinner fall at dusk is often better fishing than the hatch, and far less crowded.
- Slow, flat water is where PMD fishing gets hard. Find broken water and the same fly works.
Flies that imitate it
Each of these is a card in the deck, and each has a full page in Our Fly-brary.
Keep reading
- Dry fly vs nymph — which stage to fish, and when
- Why trout refuse your fly — usually the wrong stage, not the wrong pattern
- Best time of day to fly fish — the daily logic behind the table above
- Our Fly-brary — every fly in the deck, explained