A Classic American Fly: The Stimulator

This article, which was originally titled "An American Classic" in the April-May 2012 issue of Fly Fisherman magazine, is an excerpt from the book The Orvis Guide to the Essential American Flies (Universe, 2011) by Tom Rosenbauer. 

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You can tell a fly has reached the zenith of popularity when guides give it a nickname. “You try a Stimmy yet?” is the call often made from one drift boat to another when the fish turn off their feeding for reasons beyond our comprehension.

I was a latecomer to the magic of the Stimulator, and avoided it for years because I had not intercepted many large stonefly hatches.

I guess it struck me one day on Colorado’s South Platte River, where the typical day involves hanging size 22 or 24 midge nymphs off a strike indicator, and if you’re lucky, a size 20 olive mayfly might make an appearance.

I was fishing with Monroe Coleman, a veteran guide and dry-fly maniac. “Dry or die” is usually the slogan we yell from one side of the river to another. It was a painfully bright day and the fish were snotty.

“Think I should try 8X?” I asked.

“Why don’t you just dump your whole fly box in the river and save yourself the trouble?” Coleman replied.

“I’m going to cut back my tippet to 4X and try a Stimmy.”

I won’t lie and tell you we caught a pile of fish that day, but just seeing those sophisticated South Platte rainbows and browns turn away from gobbling diminutive subsurface bugs and rise to the top for a fly that I had previously associated with big rocky freestone rivers and giant stonefly hatches was a revelation.

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Since my epiphany, I’ve never gone anywhere without a Stimulator. I fish it in brawling Rocky Mountain rivers. I fish it in tiny brook-trout streams from North Carolina to Pennsylvania. I fish it for the educated brown trout on the Delaware River.

Sometimes I think Eastern trout anglers get too hung up on imitating what is on the water and forget that trout are opportunists, and as long as a big fly looks like something they’ve eaten over the past month, there is a chance a trout will rise to a big juicy imitation.

The Stimulator is the brainchild of Randall Kaufmann, originally from Oregon and now happily residing in Jackson Hole, Wyoming. Like many of the wildly popular fly patterns we use today, the Stimulator was an evolutionary fly.

Kaufmann learned to fish in California, Oregon, Washington, Idaho, Wyoming, and Montana in the 1960s and ’70s. There, big stoneflies hatch all spring, followed by an abundance of large terrestrial insects, finishing the season with the large orange October Caddis.

There were always big insects to imitate. As Kaufmann modestly told me: “The Stimulator as a style of fly was not a new, nor unique design, but like most ‘new’ flies it was built upon old ideas. There were several popular downwing patterns with similar ‘parts,’ including the Improved Sofa Pillow and the Royal Trude, both favorite flies of the day. I mixed the tying styles and replaced the ‘parts’ with some of my favorite materials and colors to better represent the hatches that I fished.”

But there is a difference between a novice fly tier changing a couple of materials on a fly pattern and adding his name to it, and a veteran fly tier and highly perceptive and experienced angler like Randall Kaufmann. His tinkering is the process of careful experimentation and knowledge of exactly what a material substitution will do for a fly, in terms of its effectiveness, floating qualities, and durability.

The Stimulator didn’t arise fully formed from an all-night tying session in the middle of winter in his study. It came from years of adding new materials and then putting flies to the test, with many prototypes banished to the bluegill box before the final version was ready for the rest of the world.

Besides imitating stoneflies of all sizes and colors (this fly is tied in a wide variety of color combinations), Stimulators work well in sizes 12 through 16 during caddis hatches, and in the bigger sizes it makes a decent grasshopper imitation.

I also think trout take Stimmies for moths that bumble into the river. I’ve found Stimulators very effective during hatches of the giant Hexagenia mayfly, and although to most eyes it looks nothing like a big mayfly with upright wings, it could be a credible facsimile of a mayfly emerging from its shuck at the surface.

And in small brook-trout streams where the average fish would fit into a sardine can, I’ve found that fishing a size 10 Stimulator while other anglers are fishing a size 16 Adams often helps me sort through the small fish and raise the eight-inch monsters.

Kaufmann doesn’t offer many dictums when giving tying directions for his fly, but aspects he stresses are that the wing should be wide and tall and the tail should flare.

The high wing gives the fly an impression of bulk and movement, dries quickly, and is highly visible even in foamy pocket water. The short, flared tail keeps the butt of the fly riding high, especially critical with this fly because it is often used as the dry end of a dry-dropper rig, with a weighted nymph tied to a piece of tippet that is attached to the bend of the hook.

Stimulator Variant Recipes

Original Stimulator

Hook: Curved nymph hook, sizes 6–16.
Thread: Fluorescent fire orange 6/0.
Tail: Short, flared bunch of cow elk hair.
Abdomen: Orange sparkle dubbing.
Abdomen Hackle: Brown, short.
Abdomen Rib: Fine gold wire.
Wing: Cow elk hair, flared wide and tall.
Thorax: Reddish orange sparkle dubbing.
Thorax Hackle: Grizzly, slightly longer than abdomen hackle.

Royal Stimulator

Hook: #6-16 curved nymph hook.
Thread: Fluorescent fire orange 6/0.
Tail: Short, flared bunch of cow elk hair.
Abdomen: Flame Stimulator SLF dubbing with a band of peacock herl at each end.
Abdomen Hackle: Brown, short.
Abdomen Rib: Fine gold wire.
Wing: Krystal Flash, and Mirror Flash (multiple colors), cow elk hair, and a short tuft of fluorescent hot pink yarn.
Thorax: Flame Stimulator SLF dubbing.
Thorax Hackle: Grizzly, slightly longer than abdomen hackle.

Rubber-Leg Stimulator (Fluorescent Green)

Hook: #6-16 curved nymph hook.
Thread: Fluorescent fire orange 6/0.
Tail: Short, flared bunch of fluorescent green bull elk hair.
Abdomen: Fluorescent green dubbing.
Abdomen Hackle: Grizzly dyed pale olive.
Abdomen Rib: Fine gold wire.
Wing: Fluorescent green-dyed elk hair, white calf tail, Krystal Flash, and Mirror Flash.
Legs: Fluorescent green speckled rubber legs.
Thorax: Pearlescent sparkle dubbing.
Thorax Hackle: Grizzly, slightly longer than abdomen hackle.

Foamulator (Black)

Hook: #6-16 curved nymph hook.
Thread: Fluorescent fire orange 6/0.
Tail: Black Northern Lights Loco Foam.
Overlay: Black Northern Lights Loco Foam.
Abdomen: Black Stimulator SLF dubbing.
Abdomen Hackle: Dark grizzly.
Abdomen Rib: Fine gold wire.
Wing: Krystal Flash, Mirror Flash (multiple colors), black Web Wing, dyed chocolate brown elk, and fluorescent hot pink yarn.
Legs: Black and white speckled rubber legs.
Thorax: Flame Stimulator SLF dubbing.
Thorax Hackle: Grizzly, slightly longer than abdomen hackle.

Step-by-Step Stimulator Fly Tying Instructions

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Tom Rosenbauer is vice president of marketing with The Orvis Company of Manchester, Vermont. He is the author of more than a dozen books.