Mayfly · Maccaffertium vicarium
March Brown
Also called American march brown, Maccaffertium.
Short answer
The march brown is a large mottled brown mayfly, hook size 10 to 14, hatching in May and June despite its name. It emerges sparsely over several hours rather than in a burst, which keeps trout looking up all afternoon without making them selective. It is a classic eastern and midwestern hatch.
What a march brown is
The American march brown is a large, handsomely mottled mayfly of eastern and midwestern rivers, and its name is a piece of inherited confusion — it is named after a British insect that hatches in March, while the American one appears in May and June. Its most useful quality is how it emerges: sparsely, a few insects at a time, spread across hours of the afternoon. That is the opposite of a blanket hatch, and it produces a different kind of fishing — trout stay interested all day without ever seeing enough duns to become fussy, which makes it one of the friendliest big-mayfly hatches for a newer angler.
- Hook size
- Hook sizes 10 to 14
- Colour
- Mottled tan-brown body, heavily barred and mottled wings, two tails
The stages trout eat
- Nymph
- A flat, clinging nymph of fast rocky water. A hare's ear is close enough and always has been.
- Emerger
- Emerges in the film in broken water, which is where a soft-hackle swung downstream works beautifully.
- Dun
- Large and heavily mottled, drifting a long way before flying. Easy to see and easy to fish.
- Spinner
- Falls at dusk, often mixed with other species, and frequently the best twenty minutes of the day.
When does the march brown hatch?
| When | What is happening |
|---|---|
| Late April | First emergences on the warmer southern rivers, overlapping with Hendricksons. |
| May | Peak. Afternoon emergence over several hours, with the best fishing from midday to teatime. |
| June | Tailing off, and moving to the cooler headwaters and the more northern rivers. |
| Rest of the year | Nothing on the surface, but the nymph is in the drift all year and a hare's ear never stops working. |
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
Eastern and midwestern freestone rivers: the Catskills, Pennsylvania's limestone and freestone streams, Michigan's Au Sable and Manistee, and the Appalachian waters of Virginia and the Carolinas. The New York, Pennsylvania, Michigan and Vermont pages all name it.
Fly fishing in New York Fly fishing in Pennsylvania Fly fishing in Michigan Fly fishing in Vermont Fly fishing in Virginia
How to fish it
A sparse hatch means a searching approach rather than a matching one. Fish a visible dun through likely water rather than waiting for a rise, and expect fish to come up for it from a long way down. In faster water, swing a soft-hackle through the tail of a run during the emergence — this is one of the hatches where that old method still beats a dead-drifted dry.
- Do not wait for a hatch. Fish the dun as a searching pattern through the afternoon.
- A swung soft-hackle during the emergence is the forgotten method, and it still works.
- The name is British and the timing is not. Expect it in May.
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