When does the Eastern March Brown hatch?

May–June, typically All day (sporadic). It starts from about 11°C, peaks around 15°C and tails off by 20°C.

What flies imitate the Eastern March Brown?

American March Brown, March Brown Spinner, Parachute March Brown, typically on a #12–10 hook.

Spinner stage: 10–13mm. That matches a #12–10 hook.

Mayfly · Aquatic insect

Maccaffertium vicarium

Size

10–13mm

Hook size

#12–10

Hatch window

Season May–JunePeak time All day (sporadic)

Water temperature

15° peak

11°20°

How fish feed on it

The fall comes in the evening and is a genuinely good one, better than the daytime hatch on many rivers. Big spent wings on flat water at last light.

Flies that imitate this

American March Brown

March Brown Spinner

Parachute March Brown

Ecology

Rivers & stillwaterFreestone rivers

Where you'll find this

Present throughout

Identification

Maccaffertium vicarium is a species of flatheaded mayfly in the family Heptageniidae. It is found in all of Canada and the eastern United States.