The March Brown is one of the most popular mayflies, mainly due to their size. In sizes 12 and 14, they’re incredibly visible for anglers and a hearty meal for trout. March Brown hatches typically begin in early May, although we’ve also seen them appear as early as mid-April, and can show up any time through early June. In larger sizes, these patterns can also be used to match the Brown Drake and other similarly-colored mayflies.