March Brown Gray Fox

Overview:
The March Brown, also known as the Gray Fox, is a medium to large mayfly species found in cold, fast-moving rivers and streams across North America. It is one of the first significant hatches of the spring, typically emerging in early to mid-spring, often during March and April, making it a crucial hatch for anglers targeting early-season fish. The March Brown is easily identifiable by its tan to brown body and its large, mottled wings. While not as large as some other mayflies, its emergence in significant numbers is a key event for trout, particularly after a long winter. Common hook sizes for March Brown imitations generally range from 10 to 14.

Nymph:
The March Brown nymph is a fairly large, robust insect, typically measuring about 1 inch in length. It has a light brown to olive body with a segmented appearance and a dark thorax. The nymphs are commonly found clinging to the substrate in fast-moving waters, particularly in riffles and the areas just downstream of riffles. They are most active during the pre-emergence stage, crawling along the bottom before hatching. Common hook sizes for March Brown nymph patterns are typically 10 to 14, reflecting the size of the insect.

Dry/Dun/Spinner:
The adult March Brown, or dun, measures about 1 inch in length. It features a light brown to tan body, with large, translucent wings that are often mottled with a slight grayish tint. The March Brown emerges in early spring, typically during the late afternoon or early evening, in moderate to large hatches. Trout key in on these mayflies due to their size and visibility in the water. Common hook sizes for dry flies range from 10 to 14.