Tying Skip Morris's Anatomical Mayfly Nymphs

This article originally appeared in the May 2007 issue of Fly Fisherman.

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The Skip Nymph is an all-around imitation of a mayfly nymph, and when tied in a broad range of sizes and three different colors, it effectively imitates about any mayfly trout care to eat. After 15 years of catching fish on this fly, I depend on it when I need a generic pattern to fool fish looking for mayfly nymphs. But no fly works every time–my trusted Skip Nymph included–and a more specific imitation sometimes provides an edge. That’s why I developed an anatomical series of nymphs–the Anatomical Green Drake, PMD/Baetis, and Callibaetis.

I fish mayfly hatches often enough that I like to have nymphs so convincing that I feel they can't miss, though the term "can't miss" is always relative in fly fishing. If I'm fairly certain the fish are taking, for instance, Pale Morning Dun nymphs, and especially if the fish are wise to anglers and their tricks, I'll reach for an Anatomical PMD/Baetis. I often refer to the Anatomical series as my "confidence nymphs."

When I fish an Anatomical, I never blame failure on the fly, but I always feel the fly's realism contributes when I succeed. Anatomicals have gills. They have appropriately splayed legs. They have the correct number of tails rather than a brush of fibers. But Anatomicals don't have the crawl­away perfection of an hours-to-construct, realistic pattern by Bill Blackstone or tying pioneer Bill Blades. I think Anatomicals are as detailed as they need be to convince careful trout–more detail would be for fishermen, not fish. Consequently, tying them is not unmanageable for average tiers.

Here are the three Anatomical nymphs and the major Western mayfly species they imitate.

Anatomical PMD/Baetis

Blue-Winged Olives (BWOs) and Pale Morning Duns (PMDs) are year-round staples of Western river mayfly fishing. Small, dark brown, slender, and lightly gilled, the nymphs of these two mayflies look so similar that an imitation of one imitates the other.

BWOs hatch year-round but are most important from fall through early spring when few other mayfly, stonefly, or caddis species are hatching to compete with them. BWOs prefer cloudy, even foul, weather (though they will hatch in sunshine) and typically appear between 11 A.M. and 4 P.M. To imitate BWOs I fish Anatomical PMD/Baetis nymphs in two ways: Right along the bottom in the hour before the hatch, when the trout know to look for the active nymphs; and near the surface, dangling from the bend of a dry fly's hook on 8 or 10 inches of tippet, to rising trout that seem to want neither an emerger nor a dry fly.

PMDs are generally the longest- and strongest-hatching summer mayflies on Western rivers. Like BWOs, they prefer cloud cover but also hatch briefly in the sun­ shine. They hatch from around 11 A.M. to 1 P.M., but later in the season they hatch in the earlier and later hours, lying quiet during the hot part of the day. They return to midday hatching in the fall. When there is no hatch in good PMD water, I often fish my Anatomical PMD/Baetis as a dropper above a heavy stonefly nymph in riffles and other lively currents. But an Anatomical PMD/Baetis fished a few inches below a dry fly can be just the thing when duns are hatching and trout are up feeding on them.

Anatomical Callibaetis

Of all the mayfly species that live in North American lakes, Callibaetis are the most common and widespread. They abhor sunshine and rarely hatch without cloudy or even rainy skies. They normally hatch from around 10:30A.M. to early afternoon, but I've also seen them coming off into the evening hours, with trout feeding on them the whole time. Callibaetis produce up to three broods in a season; the first in early spring is large (#12), the second in early summer is smaller (#14); and the fall hatch smaller yet (#16). I try to keep plenty of #l 4 nymph, emerger, and dry-fly imitations on hand–the trout always seem to take this size, regardless of which brood of Callibaetis is hatching.

When trout are rising during a Callibaetis hatch, a dry fly or emerger makes perfect sense–yet the nymph can some­ times outproduce both. When the trout prefer nymphs, I fish my Anatomical Callibaetis from just under the surface–so it's nearly exposing its wingcase–a foot or two below the surface with a slow and varied hand-twist retrieve. Before the hatch, an Anatomical Callibaetis fished near weedbeds can stir up some action. In clear, weedy lakes–the best Callibaetis lakes–when nothing is hatching, I often cast or troll an Anatomical Callibaetis on a fast-sinking, full­-sinking line.

Anatomical Green Drake

Fly fishers dream of catching heavy trout on big Green Drake dry flies. And dry flies do work, but sometimes–as with most mayfly hatches–nymphs are best. A Western Green Drake nymph is something of a brute–fluffy gills line its stout abdomen and its powerful-looking legs emanate from its full thorax that appear somewhat hunched beneath its wingcase.

Western Green Drakes emerge from late spring through summer from fast water on overcast afternoons, typically from 11 A.M to 4 P.M.

I've not forgotten that the Skip Nymph series has caught lots of tough trout across the U.S. in Canada, and overseas. And I still think it is the best choice when I'm not certain what the trout are taking–after all, impressionistic nymphs may suggest several possibilities, increasing the odds of covering the correct insect. But if I'm convinced the trout are onto the nymph of a specific mayfly species, please hand me an Anatomical.

Anatomical PMD/Baetis Fly-Tying Recipe

• HOOK: #14-18 (PMDs) or#l6-20 (Baetis) Daiichi 1560 or equivalent. For#14-16, use 1XL, heavy wire and for #18-20, use regular­length, light-wire hooks.
• BEAD: Black metal (1/16" for #16 and sma11er; 5/64" for #14).
• THREAD: Brown or dark brown 8/0. WEIGHT: .015" diameter lead or lead­free wire (fine), or fine copper wire for #18-20.
• TAILS: Three pheasant-tail fibers. RIB: Fine gold wire.
• ABDOMEN: Pheasant tail fibers. WINGCASE: Brown Stretch Flex or Medallion Sheeting.
• LEGS: Brown or olive-brown partridge.
• THORAX: Brown or dark brown rabbit fur.

Anatomical Callibaetis Fly-Tying Recipe

• HOOK: #12-16 Daiichi 1560 or equivalent.
• BEAD: Black metal (5/64" for #16, 3/32" for #12-14).
• THREAD: Brown or tan 8/0.
• WEIGHT: .015" diameter lead-free wire over the front half of the shank.
• TAILS: Three mottled brown turkey quill or pheasant tail fibers.
• ABDOMEN: Hare's mask.
• GILLS: One large, brown dry-fly hackle, with fibers trimmed short.
• BACK: A strip of mottled turkey quill.
• RIB: Fine gold wire.
• WINGCASE: Mottled brown turkey quill (a strip of clear or light brown Stretch Flex, Scud Back, or Medallion Sheeting over the turkey is optional) or a tough synthetic sheeting, such as Thin Skin, in turkey quill color.
• LEGS: Natural brown (or gray) partridge feather fibers.
• THORAX: Same dubbing as in the abdomen.

Anatomical Green Drake Fly-Tying Recipe

• HOOK: #8-12 Daiichi 1710 or 1260 or equivalent.
• BEAD: Black metal (5/64" for #12; 1/8" for all other sizes.
• THREAD: Brown 6/0.
• WEIGHT: .015" diameter lead-free wire.
• TAILS: One dark olive or brown partridge feather with its stem closely trimmed, a bunch of two or three fibers remaining on each side.
• RIB: Fine copper wire or UNI monofilament thread, 4 mm.
• BACK: A slim strip of olive-brown or brown Stretch Flex, Medallion Sheeting, or substitute.
• ABDOMEN: Two green and one brown ostrich herl spun in a dubbing loop, trimmed underneath after the back and rib are added.
• WING CASE: A strip of olive-brown or brown Stretch Flex, Medallion Sheeting, or substitute.
• LEGS: Olive-brown or brown partridge.
• THORAX: Peacock Arizona Synthetic Dubbing.

Step-by-Step Fly-Tying Tutorial

1. Slide a bead onto the hook shank so that the small end of the bead's hole is against the hook eye. Do not use eyes if you are using a bead. Insert the hook into the vise.Wind a layer of lead-free wire from just behind the center of the shank to the bead. Break or cut off the ends of the wire, then push all the wire up against the bead.(If you use eyes instead of a bead, bind them atop the shank and then dub around them later.)

2. Start the thread just behind the wire. Bind three turkey quill fibers along the shank to the hook bend. Pull the two outside fibers out, and then take a few turns of thread over the center fiber and against the rear of the side fibers–the tails should now be spread and equal to half to two-thirds the shank length.

3. Bind a section of turkey quill on top of the shank, behind the wire, to the bend.The section should be about half the width of the hook gap.

4. Trim both sides of a large dry-fly hackle, leaving stubs about 1/8-inch long. (Or you can strip one side and trim the other, which tends to come out a little neater.) Bind the hackle by its tip, up the shank to the wire.

5. Tie in gold wire on the far side of the shank and secure it to a point just short of the bend. Dub a tapered abdomen from the tails to slightly past mid-shank.

6. Trim off the butts of the turkey, hackle, and gold wire. Wind the hackle up the abdomen with five to eight turns. Bind its end at the front of the dubbed abdomen.Trim the butt of the hackle.Trim the hackle fibers only on top of the abdomen.

7. Draw the strip of turkey forward on top of the abdomen and bind its end. Rib the abdomen with the gold wire.Try to avoid tying down hackle fibers under the wire; pull the trapped fibers out with your bodkin or zig-zag the wire through the fibers. Bind the end of the wire at the front of the abdomen. If the gills (hackle fibers) look a little long, trim them slightly along the sides. Use the photos from step 9 as a guide to gill length.

8. Trim the ends of the turkey section and wire.Tie down a slim strip of Stretch Flex over the wire, back to the abdomen. Bind another section of turkey, about two thirds as wide as the gap, on top of the Stretch Flex.

9. Strip the fluff from the base of a partridge feather.Strip most of the long fibers off the sides.Try to keep the tips even. Bind the fibers (tips forward) halfway between the bead and abdomen.Trim the butts and bind them.

10. Pull the fibers back firmly and crease them upright with your thumbnail. Set the fibers upright by building tight turns of thread up against them.

11. Dub a thorax up to the bead.

12. Divide the fibers, and pinch them with your thumb or with something flat and hard like the sides of your scissors blades to splay the fibers like real nymph legs.

13. Pull the turkey section forward over the abdomen. Bind the section behind the bead with several tight turns of thread. Pull the Stretch Flex over the turkey and bind it at the bead.Trim both closely, whip-finish, trim the thread,and add head cement to the whip-finish.Trim the hackle fibers on the underside of the abdomen if you wish.

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Skip Morris is the author of more than ten books on fly fishing and tying.

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