The March Brown fly is a versatile dry fly that covers various mayfly hatches, including March Browns, PMDs, and other brown-bodied mayfly hatches.
 
The March Brown fly is a classic fly pattern that imitates the natural hatching of the March Brown mayfly. It is characterized by its sailboat-like appearance, with a dark brown body, mottled wings, and a distinctive dun form. 
 
The nymph is flat and broad, with a reddish-brown to tan mottled coloration and plate-like gills. The adult fly has heavily mottled brown wings and a tan/brown body with distinct segmentation. March Browns are known for their sporadic hatch behavior, where they emerge from the water column in small numbers, making them a reliable food source for trout transitioning out of winter feeding patterns. 
 
They are typically found in fast, rocky riffles and runs, requiring clean, cold, highly oxygenated water.