Split Case Mayfly Nymph

Split Case PMD

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Tying Instructions

1. Attach the hook to the vise. Make sure that the point and barb do not get pinched by the vise. Lay a thread foundation from behind the eye to the bend of the hook. You can verify this position by hanging the thread down with the bobbin and it should intersect with the middle of the barb.

2. Snip a small number of fibers from the Mallard Flank Feather with the tips even. Measure the length of the fibers against the shank, the tail length should be about 2/3 the shank length. Bring the fibers against the shank at the bend of the hook nearest to you. The thread pressure will bring the fibers to the top of the shank by it’s tension. Secure the fibers to the top of the shank with thread wraps.

3. Snip off the butt end of the tailing fibers behind the eye and secure with thread wraps. Place a piece of wire ribbing under the shank, behind the eye, and secure with thread wraps, wrapping back to the tail tie-in position. Try to keep the wire positioned at the bottom of the shank.

4. At the tail tie-in position, apply a small amount of Superfine Dubbing to the thread. Slide the dubbing up the thread so that some of the fibers touch the shank. Give on wrap of the dubbed thread around the shank to secure the fibers. Now, you can twist the fibers further for a tighter dubbed thread to create a thin abdomen.

5. Dub a tapered abdomen to just beyond the midpoint of the shank. You might have to add some additional dubbing to get a taper.

6. Wrap the wire ribbing forward with about 5 equally spaced turns. Clip off the butt end of the wire and secure with thread wraps.

7. Attach two Black Goose Biots by the butt ends behind the eye. Secure the biots with thread wraps to the abdomen. Note that there is a slight crossing of the biots with some overlap. This will give me a slight split effect. You can increase the split effect by placing the biots further down along the side of the shank.

8. Attach a thin section of Yellow .5mm razorfoam to the top of the shank behind the hook. I like to trim a small point to the material for securing. You can use white foam and mark it with a Yellow Highlighter. The edges of the foam should not exceed the width of the biots along the side edge, so make sure you use a thin section. Secure with thread wraps.

9. Dub a thorax that is about twice the diameter of the abdomen. You might need to add dubbing as you go but, always, keep the amounts small.

10. The thorax should be a tightly wrapped ball, taking care not to crowd the eye.

11. Snip two small segments of Mallard Flank Fibers for the legs. Attach each segment just behind the eye to the top of the shank in a crossing position.Secure with only a couple of thread wraps.

12. You can pull on the butt ends of each segment to adjust the length of the legs. I like to adjust the length so that they just exceed the length of the thorax. Then secure with 3-4 tight thread wraps.

13. Pull the foam over the thorax and secure the foam just behind the eyes. Note the the edges of the foam do not exceed past the center of the thorax, allowing the legs to still splay out along the side of the thorax.

14. Next, pull the two biots forward and secure these just behind the eye. Note the split, allowing the yellow foam to spot through. Secure with thread wraps.

15. Trim off the butt ends of the biots and wrap a small thread head. Whip Finish.

Materials to Order Material, click the link
Hook	Daiichi 1710 #16-20
Thread	Uni-Thread Brown 8/0
Body	Mahogany Brown Superfine Dubbing
Thorax	Mahogany Brown Superfine Dubbing
Tail and Legs	Natural Mallard Flank Fibers
Wingcase	Black Goose Biots
Wingbuds	Yellow Speckled 0.5mm Foam
Ribbing	Ultra Wire, small, Hot Yellow

Joe Mitchell

Split Case Mayfly Nymph

Certain mayflies will split their wingcase while emerging from the water column. This exposes the wing and is a triggering mechanism for many trout to strike. Joe Mitchell of Heber City, Utah came up with the Split Case Mayfly Nymph pattern while guiding on the Provo, the pattern has gained a wide acceptance among many guides within the Sierra and throughout the West. The pattern is marketed by Solitude Flies.

Black Biots are used for the wingcase but you could substitute this with Black Thin Skin or Scudback. The foam wingbud on the Split Case Mayfly Nymph is .5 mm thick. You can color this foam to any triggering color you prefer, yellow is preferred by most. Try varying the spacing between the biots for different exposures of the wingbuds.

Ultra Wire is used to create a segmented abdomen. Superfine Dubbing is used as the body material for the PMD and BWO. These are small patterns, size 18-20, that need a less bulky material. The Green Drake pattern is much larger and using a nymph dubbing, such as Mercer’s Buggy Nymph, will work better to allow the nymph to submerge properly.

Tungsten Split Case BWO

Hook	Daiichi 1710 #18-22
Thread	Uni-Thread Olive 8/0
Head	Tungsten Bead, Black
Body	Blue Wing Olive Superfine Dubbing
Thorax	Mahogany Brown Superfine Dubbing
Tail and Legs	Olive Dyed Mallard Flank Fibers
Wingcase	Black Goose Biots
Wingbuds	Yellow Speckled 0.5mm Foam
Ribbing	Ultra Wire, Golden Olive, small

Split Case Green Drake

Hook	Daiichi 1710 #10-12
Thread	Uni-Thread Olive 8/0
Head	Uni-Thread Olive 8/0
Body	Mottled Nymph Dubbing, Hares Ear
Thorax	Mottled Nymph Dubbing, Hares Ear
Tail and Legs	Coq de Leon Fibers, medium dun
Shellback	Pheasant Tail Fibers
Wingcase	Black Goose Biots
Wingbuds	Yellow Speckled 0.5mm Foam
Ribbing	Ultra Wire, Olive, Brassie