These olive green or dark brown colored, medium-sized clinging nymphs are loved throughout North America for their prolific early-season hatches in fast water. March Browns in the nymph stage are easily identified by their wide and extremely flat bodies, broad heads, large upward-looking eyes, and three long tails. These insects follow the common life cycle of mayflies and thrive in the rocky substrate of well-oxygenated and rapidly moving aquatic systems. They are prolific in very fast riffles, current seams, and the lower energy areas below and near these high energy environments. March Browns emerge to adult duns during the morning and afternoon hours of the early portion of the season (March through May). As winged adults these mayflies display characteristic speckled wings, banded abdomens, low-profile heads, and long twin tails. The March Brown’s wide distribution and long hatches make this a favorite offering of fly anglers itching to fish the early season action after a long winter of fly tying, rod-building, and dreaming of fly fishing.
Favorite local March Brown Hatch is on the Trinity River. Catching Steelhead on a dead drift dry fly is pretty awesome. Not to mention the river is usually pretty empty. You will want to have March Brown in your box from March through May on many of California's rivers.