During its adult life stage, these relatively large mayflies are often found floating along the water’s surface before quickly retreating to the safety of streamside vegetation. March Browns hatch throughout the United States during early spring (March through May) and are considered one of the best early season hatches on many of North America’s best fly water. Nymphs and emergers are active throughout the morning and afternoon, and when a hatch is on, trout can quite literally have their pick of these protein rich bugs. March Brown duns are known for their relatively rapid emergence and characteristically long downstream drifts. These classic mayflies are often likened to a fleet of tiny sailboats drifting through riffles, runs, and gentle eddys. In the Dun stage the mayfly still has mouthparts so it must eat and drink in order to stay alive to store energy for its next molt.
Traditional Dry Fly tactics. Casting upstream and keeping a tight line to your fly as it drifts down. Focus on edges and clean drifts.
After hatching into winged adults, March Brown duns will flutter to nearby foliage and vegetation prior to mating. After emergence, males will create large mating swarms above faster riffles and females will fly into these clouds of sexually mature males. After the females are fertilized, they will deposit their eggs on the surface of the faster water. Both males and females will fall as spent spinners to the surface film, some will float high on the water and others will be swept below the surface. The Spinner will have more color on its body and also will have clear wings. Falls of March Brown spinners can be very thick and when the water is thick with these spent bugs, trout rise feed voraciously on the surface.