Meant to simulate a number of Rithrogena (clinger) mayfly species emerging to speckled winged adults, ‘March Brown’ is a tag applied to nearly as many versions of the fly as there are fly tyers &, in some form, has been described since the earliest English literature.
Rithrogena prefer streams with good flow, & larger freestones may produce great hatches. Those species we refer to as March brown begin emerging before spring run-off, as early as February in southern & coastal regions, later at higher elevations & northern regions. Generally, these appear around late April in
NE Washington, & I see them on into June some
years. Though they don’t produce great hatches on my home water as they do in
many places, they are enough of a presence through their hatch season that the
imitation fishes well through the period.
Looking at naturals found at various locations, one isn’t surprised at the great variety of patterns meant to cover March brown. Adults may be #12-#16 (nymphs, a size larger). The color of mature nymphs may range from tan through all shades of brown, olive/brown, & olive, depending on location. Each stream holds its own color variant. (An aquarium net might satisfy the curious.) Considering the variety of colors & materials meant to simulate these, I am drawn, once again, to the notion that: presentation, size, silhouette, are primary factors, over color. And in this case silhouette is indeed important, by my own thinking, as the broad-thoraxed, teardrop shape of the naturals is a keying visual characteristic.
One of James Leisenring’s salient contributions to the soft-hackle style was his refinement of silhouette, which he considered important to the fly’s effectiveness, & for that reason many of his patterns call for a thorax, & though not his own invention, it is a fair departure from most of the older soft-hackle designs. Jim Leisenring’s well-thought version still stands as a killing pattern for covering March browns.
Neil Norman, author of Soft Hackles, Tight Lines, an Online Soft-Hackle Pattern Book, lays out an excellent historic profile of March brown, describing several notable dressings. For any interested in the history of our flies, Neil’s journal is an invaluable archive.
Jim Leisenring's March Brown
Hook: #10-#14 (Mine is tied on a #12 Mustad 3906B)
Thread: orange silk (orange or rusty-brown UNI 8/0 substitutes)
Hackle: brown partridge
Tail: 3 cock pheasant tail swords
Rib: gold or silver wire wound over the abdomen
Abdomen: 3 or 4 cock pheasant tail swords twisted with a tag of the thread
Thorax: hare’s mask, dubbed fairly heavy