The RS II: A Mayfly Emerger That Has Stood the Test of Time

The next fly on the list of ETU Top Twelve Flies is the RS II. It is certainly no surprise that this emerger pattern has found a place in anglers' fly boxes for many years. Originally developed by master fly tier Rim Chung, it has proven to be one of the most effective flies of all time on the South Platte.

In his book, A Flyfisher's Guide to the Soute Platte River, Pat Dorsey repeatedly cites the effectiveness of this pattern and features it in the chapter about flies he uses on the South Platte. Dorsey relates that not only did Rim teach himself to fly fish; he also taught himself to tie flies. The RS II is perhaps Rim's most famous invention and is a variation from an earlier model that he named the RS I. It features an emerging wing in place of the wing case that he used in the original. Dorsey explains that the name RS II stands for “Rim's Semblance No. 2.”

Because of the RS II's track record, it is also no surprise that many other tiers continually devise variations for this fly. Most popular variants substitute materials for one or more components of the fly, but for the most part, the basic pattern remains unchanged. Clearly, this fly is based on a solid design that continues to fool even the most wary trout. Pat Dorsey says he likes to combine the RS II or one of its variations with his Black Beauty when fishing the South Platte tail waters in the spring and fall. With this tactic, he covers emerging baetis and midge pupae at the same time. But don't rule the RS II on other waters in Colorado and elsewhere whenever you see mayfly activity. For example, you can rig an RS II behind a caddis dry fly for those partly cloudy days on the Arkansas River to have both caddis and mayfly patterns available. Guides there say that baetis activity can abruptly increase during periods when the sun is obscured and that having an emerger like the RS II as your second fly can be an effective tactic as conditions change suddenly.

The example shown here closely resembles Rim's pattern. CDC is used for the wing in place of the saddle hackle webbing in the original recipe. For this angler, it has fooled the big Browns in Cheesman Canyon; and they surely have seen just about every pattern one can imagine. I have taken large fish there with this pattern during spring and early summer in surprisingly shallow water. It is shown here in gray, but can be modified with colors and materials as needed.

Tie up your RS IIs in a variety of colors from size 18 to 24. In the smaller sizes, you might consider using just the thread to form the abdomen, since even a small amount of dubbing may create too much bulk.

Head to your favorite stream and see if the RS II doesn't just do the trick when you see mayflies starting to emerge! As mentioned, it can be fished behind a dry fly in the surface film, or further down the water column using a variety of nymphing configurations. Watch for subtle takes, then set the hook and hang on!


Hook: Dai Riki 310 or TMC 101, sizes 18-24
Thread: Gray Sheer 14/0 or UNI-Thread 8/0
Tail: Dun Micro fibets, split
Abdomen: Gray Super-Fine dubbing or muskrat fur
Thorax: Gray Super-Fine dubbing or muskrat fur
Wing: Gray CDC puff

Tying Instructions

Crimp the barb on the hook and tie in your thread behind the eye, leaving a tag end about three inches long. Wrap back to the top of the bend and form a small thread ball that will serve to separate the tail fibers.

Tie in two micro fibets together with a pinch wrap on top of the shank against the thread ball so they extend about one hook shank in length past the bend. Take a couple of wraps forward, then draw the tag end of the thread up and forward splitting the micro fibets. Apply firm forward pressure on the tag end to separate the two tail fibers while wrapping the thread forward about three-quarters of the way toward the eye. Trim the tag end of the thread along with the butt ends of the micro fibets.


Spin your thread to unwind it and flatten it, then spiral it back to the tie-in point at the tail. Sparsely dub your thread with superfine dubbing or natural muskrat fur, then build a tapered body working the thread forward to a point about one-third to one-quarter of a hook shank behind the eye. Using sparse amounts of dubbing is the name of the game here. It is very easy to build up too much bulk, so apply the dubbing sparingly and make every thread wrap count!


Tie in a CDC puff with a pinch wrap followed by one or two securing wraps. Tie in the CDC so it is slightly on the long side. Once tied in, pull the tag end of the CDC through the wraps to shorten the wing to the desired length. Leave enough length to allow the wing fibers some freedom of movement. Trim the tag end of the CDC once you have adjusted the length of the wing. I can usually get about three size 18 or smaller flies out of one CDC puff.


Dub behind and in front of the wing, then taper down to the eye. Form a neat head and whip finish to complete the fly. Apply a tiny amount of Gloss Coat or other dressing to the head and you are done.


You may have to tie a few before you get the wing placed where you want it and get the correct proportions with your dubbing. But with some practice, this fly becomes pretty easy to tie.

Photos and article by Tim Stechert