Pros: Excellent flotation; Readily adaptable; Relatively easy to tie
Cons: Sometimes almost too popular
Every once in awhile, someone 'invents' a fishing fly which suggests a variety of food forms, while imitating nothing specifically, proves ubiquitously useful in a variety of sizes and guises, is relatively simple to tie, and thereby acquires a level of popularity that virtually every fly shop has a few for sale. In a simpler turn of phrase, the fly becomes a "classic." Such has been the fate of Randall Kaufmann's Stimulator dry fly.
What Is It?
The Stimulator is simultaneously nothing and a variety of things. It is what flyfishers refer to as an "attractor" pattern. An attractor pattern is a fly that 'attracts' a fish's attention by representing certain aspects of what fish see as food; e.g., actual motion or the illusion thereof, color, profile, etc. Typically, an attractor pattern combines a number of these aspects - something that the Stimulator does in spades. The Stimulator can be used to imitate caddis, stoneflies, hoppers, beetles, and cicada. It is extremely useful as an indicator fly; i.e., tie a nymph on a short length of monofilament off the hook bend and the fly acts as an indicator, not to mention potentially attracting a fish that may prove reluctant to take a dry, but then sees the nymph and takes that.
Randall Kaufmann is a noted Pacific Northwest fly tyer, lecturer, angling author, and owner of Kaufmann Streamborn, Inc. In the 1995 revised edition of his book Tying Dry Flies, he states of the Stimulator:
"I don't know why the Stimulator is so effective. Perhaps the light pattern or surface impression... Maybe the silhouette or color combination... possibly other characteristics not yet contemplated... The pattern is not unique, and it closely resembles many other downwing patterns. I have borrowed the "parts," incorporated some of my favorite materials and color combinations, and subtly improved on the tying style... Much of the Stimulator's success can be attributed to versatility and the many size and color possibilities... Even a subtle change, like thread color, sometimes seems to make a difference." - p. 102
Hook: I've seen the Stimulator tied on a variety of hooks. However, the "correct" hook style would be the TMC 200R or equivalent. (see The TMC 200R: "Mess With The Best, Catch The Rest and To Good To Be True? Then You Probably Just Got What You Paid For )
Thread: I've used 8/0 Gudebrod and 8/0 Uni for most of my Stimulators in sizes 12 - 16. For sizes 8 and 10, I prefer the 6/0 Uni due to the larger clumps of hair used; i.e., the 8/0 'cuts' too easily on the hair when trying to tighten down on that large a group. Color is going to depend on your aesthetics and the effect you're trying to create. Kaufmann tends to a fluorescent orange as yet another attractor aspect; i.e., an 'head' that contrasts (not to mention emulates the coloration on some stoneflies).
Tail: Elk Hair. Kaufmann calls for Elk. Elk hair has more floatation and gives more 'bulk' (while not being too 'bulky') to the body for a given size than does deer hair. The color will be dependent on what you're trying to imitate, but the most often used is light/natural elk. (Rocky Mountain Dubbing Co. has a fantastic selection of elk hair in a variety of colors and sizes.)
Rib: Depending on size, X-Small, Small, or Fine wire. Again, the most often used color is gold. But, depending on the effect you're trying to achieve, colors such as copper, black, hot orange, and even purple (wine) have worked.
Abdomen: Here's where we get into debate, discussion, and heated discourse. Kaufmann has cited Antron as well as goat/Hare-Tron mixes. I've seen some tyers use polypropolene yarn. Kaufmann even has a Royal Stimulator with a peacock/floss abdomen much like the Royal Wulff (see I Do Seem To Always Have A Few ) Then there have been those...
Well, let's just say that there are presumed reasons behind the choices. For example, poly yarn adds flotation and bulk without the need for a lot of dubbing in the larger versions. However, in my opinion it adds too much bulk; both from a tying and a fishing perspective. Let's just say that for size 16 & 18, I prefer Superfine dubbing. For sizes 12 & 14, I tend to my own mix of dubbing; typically using Hareline dubbing as a base. While I will sometimes use this dubbing mix for my not-too-often used sizes 8 & 10 (though there was this brown trout and an absolutely picture-perfect dry fly take on the Gallatin River... uh ... well), I've found myself somewhat enamored lately of Uni-Yarn; primarily due to its easy use on those sizes, good flotation, and the available colors seem to be tailor-made for Stimulators.
Wing: Elk Hair
Thorax: Same discussion as with the abdomen. However, it is fairly typical that the thorax and abdomen do not match in color; e.g., yellow abdomen/orange thorax, green abdomen/yellow thorax, etc.
Hackle: Quality dry fly hackle, palmered over abdomen and thorax. Again, the color used over the abdomen, generally, is different from that used over the thorax; e.g., brown abdomen/grizzly thorax, ginger abdomen/badger thorax, etc. One thing to bear in mind about the hackle is that due to the hook style and generally design, the hackle should be undersized by one or two sizes to maintain proper proportioning. For example, a size 10 Stimulator will require size 12 or even size 14 hackle.
Tie in the tail just above the hook barb, flaring the tips slightly. Then wrap the tag ends to cover approximately two-thirds of the hook shank length and trim. The amount will be dependent on hook size and your aesthetics. Remember, the tail and the hair underbody give the fly a good deal of its flotation; but, you don't want to create too much bulk. In the vein, do not cinch down too tightly on the underbody. A very slight 'ribbed' effect will allow the hair to maintain floatability; i.e., trapped air.
Tie in the wire rib so that it extends beyond the tail. Begin dubbing your abdomen just above the barb and move forward to the end of the hair. Tie in your chosen hackle at the forward end of the dubbing and Palmer (wrap with even spaces) the hackle back to the tail such as you would with an Elk Hair Caddis (see It's A Classic: With A Captial "C" For Caddis ) Tie down the hackle with a couple wraps of the wire rib, then wrap the wire forward in evenly spaced turns to wrap down/reinforce the hackle. Tie of the wire at where the dubbing ends. When I clip off the tag end of the hackle at the tail, I tend to add a small drop of Dave's Flexament (see Add Flexibility To Your Fly Tying ) to the conjunction of wire and hackle at the tail to reinforce the tie-in; being very careful not to use too much where the tail gets glued together.
Next, tie in the wing. I find that if you measure the length so that it goes from the 2/3 hook shank length mark to about half the length of the tail, once tied in and flared, the tips will end up just beyond the hook barb; creating a nice impression vis a vis the tail. Make sure that the wing is flared around the top 180 degrees (maybe just a little less) of the hook shank. This will add both flotation and stability to the fly. Clip the tag ends short enough that, when wrapped down against the hook shank, they form a nice tapered underbody ending about 1/2 - 3/4 of the hook eye length behind the eye of the hook.
Tie in the hackle color of your choice, then dub/wrap the thorax. Palmer the hackle forward using about 3 - 4 evenly spaced turns. Then add a thread head. This head should complete the taper of the thorax so that it flows in a single line to the hook eye.
Again, bulk is not the watch word. Flotation stems from the properties of the dubbing, hair, and hackle. While you may not ever achieve the truly tight ties found in fly bins (bear in mind just how many flies each commercial tyer does), you should strive for a certain "delicacy." I know. it's one of those "Zen things" - an inherently bulky pattern that is simultaneously delicate. It's one of those you'll-know-it-when-you-achieve-it pursuits.
All of the materials incorporated into the Stimulator are intended to give the fly great buoyancy. This makes it perfect for heavy water or high visibility is a must. (It's also what makes it an excellent indicator fly - easy to see and will support the weight of a nymph.) It also makes this fly perfect for skittering across the surface; the flared wing adding to the perception of the fluttering wings of skittering caddis/stoneflies.
These properties do come at a bit of price, however, when it comes to casting. You'll have to open your loop a bit to accomodate the increased air resistance when casting; particularly in the larger sizes. You're also likely to need a slightly heavier tippet to turn the fly over. As an example, I first started using Stimulators on a regular basis with a 4 wt. fiberglass rod. I had been using 7X tippet and was getting frustrated that I was having a little trouble controlling the size 14 Stimulator insofar as delivering it to some mighty small pockets in a small stream; especially with even the lightest down canyon breeze. The 7X was getting me into quite a few more fish than others seemed to be finding. I reluctantly moved up to 6X and found the delivery a trifle easier; with no fewer takes perceived. Realizing that, "go big or go home," might apply to more than just the fish size, I switched to 5X and enjoyed the rest of the day. Remember, the Stimulator is an attractor. In that sense, the fish are attracted to and focused on the 'food' in front of them. Given that the Stimulator, in a given size, is a relatively big piece of meat, the fish don't tend to be as finicky when it comes to tippet size.
I'd say the single, most commonly used Stimulator is the Yellow; light elk hair tail/body, yellow abdomen/thorax, brown hackle abdomen, grizzly hackle thorax. The reason? First, it represents the Little Yellow Stonefly which can be found throughout the West from as early as mid-May to as late as mid-September; with the height of the 'season' being mid-June to late-August. Second, it makes a passable hopper imitation during July and August. Finally, the light wing and yellow thorax are very visible.
Umpqua Feather Merchants is the primary, commercial, purveyor of the Stimulator; although, as it is now generally considered a 'classic' pattern, many companies produce their own variations. There are now rubberlegged versions available (i.e., small rubber legs extending from the 'thorax' adding motion) which can be extremely effective. At the moment, Cabela's even offers a 16-piece assortment of Stimulators. Individually, the commercial versions will run between $1.50 and $2 each.
Recently, I have come across some fly anglers who spurn the Stimulator for no reason other than it is so popular. There is a certain logic to it in that fish can become somewhat desensitized to flies they see regularly; i.e., something you see all the time can become less attractive than something brand new. However, in the case of the Stimulator, it is so easy to tweak the fly's appearance with a simple change in color for dubbing or hair or hackle or combination thereof, that you don't have to be fishing the same version as "everyone" else. Black hair/orange dubbing and you have a big Pteronacys imitation in June. Natural Elk/light orange dubbing and you have a more than passable October Caddis imitation in October and November. Golden brown hair... Well, you get the idea.
In a very real sense, the Stimulator can stimulate not only your fishing, but your fly tying as well...