Thorax Dun

Baetis Thorax Dun

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Tying Instructions

1. Attach thread and apply a small thread mound at hook bend. I like to start the thread at the location where I’ll place the wing, it gives a point of reference.

2. Tie in 5-6 Blue Dun Hackle fibers for the tail, one length of hook shank. The thread mound will splay the Dun Hackles when the thread is tightened behind the mound. Wrap the butt ends of the microfibetts to the wing tie-in position.

3. Tie in a 1/4″ wide section of Turkey Flats for a wingpost. Keep the tips of the flat aligned. Wing should be about the length of the hook.

4. Lift the butt ends of the Turkey Flat and trim at an angle. Secure the butt ends with thread wraps. Apply a couple of wraps beneath the wing to lift it up and secure against the butt wraps.

5. Wrap the thread back to the tail tie-in position and place a thread wrap between the fibers so they achieve a 45 degree split.

6. Apply a small amount of dubbing to the thread and wrap a tapered abdomen up to the base of the wing. Apply some additional dubbing around the wing base with some “X” wraps from behind the wing base to the front of the wing base.

7. Select a Light Blue Dun Hackle that is one size smaller than the standard for the hook size. I’m using a size 18 hook, so this hackle is size 20. Anchor the base of the hackle in front of the wing with the hackle pointing to the rear.

8. Select a second hackle that is one size larger than the standard to the hook size. On this fly, it is a size 16. Anchor the hackle at the same position as the first hackle.

9. Wrap the larger hackle so that it is forward of the wing on the top of the shank and behind the wing below the shank. 3 wraps is normal and secure the tag end with thread wraps just behind the eye.

10. Trim off the tag end and apply a few more thread wraps. Attach the hackle pliers to the second hackle for wrapping towards the rear.

11. 3 wraps is usually enough. This hackle will cross the first hackle just below the wing. Secure the tag end just behind the eye with some thread wraps.

12. Trim off the tag end and wrap a small head. Whip finish.

Materials to Order Material, click the link
Hook	TMC 100 #16-20
Thread	Uni-thread Olive 8/0
Body	Golden Olive, Superfine
Tail	Light Dun Microfibetts
Wingpost	Medium Dun Turkey Flat
Hackle	Light Dun Hackle

Vince Marinaro

Thorax Dun

The Thorax Dun is a variation off the Catskill Dry by Vince Marinaro. During the 1940’s , Vince examined the smooth waters of the Letort Spring Run in Pennsylvania and concluded the need to develop a fly that would more realistically represent the silhouette of the mayfly than the Catskill Dries did.

He noted that trout rises on the Letort were dependent upon the profile of the wing and the appearance of the fly from under the water. He also saw that the mayflies were supported on the water by their legs, not it’s body or tail. As a result, there was a need to redesign the Catskill.

Redesign of a Catskill

Vince redesigned the standard Catskill Dry so that the wing was positioned further back towards the middle of the shank to balance the fly. Since the body needed to be elevated above the water surface, Vince heavily hackled both behind and in front of the wing. Two hackles would be required since long genetically improved hackles were not available at the time.

X pattern for the hackles

Thus, two hackles would be attached on the shank in front of the wing. One hackle would be one size larger than standard and would be wrapped in an X pattern with the top hackles forward of the wing and the bottom hackles behind the wing. The second hackle would be one size smaller than standard and would be wrapped in an X pattern crossing the first. The top hackles would be behind the wing and the bottom hackles would be in front of the wing.

This type of hackling allowed the fly to keep all it’s parts above the water, except the legs. Later, when longer genetic hackles were available, Vince would wrap the X pattern with just the one hackle. Vince also found that the color of the wing needed to match the color of the mayfly it was to represent. He insisted that the hackles should also match the color of the wings. However, the color of the body was secondary to the color of the wings and hackles. In addition, Split tails were also designed into this pattern to help stabilize the fly on the water surface.

Other Thorax Duns

Today, most thorax dun patterns continue to be tied with a single hackle but not in the X pattern that Vince used. Some tiers just hackle behind and in front for the wing. The hackle fibers are clipped at the bottom into an inverted V shape. This is a technique that Mike Lawson of St. Anthony, ID made popular and would extol this pattern for Spring Creeks and other smooth waters. It is certainly much easier to tie with one hackle. Within the Sierra, the pattern is especially applicable to the Lower and Upper Owens River during low flows. Larry Medina came up with a nice variation, the Gray Thorax Dun, which he used during the evening hours on some high elevation Sierran streams.

Thorax Dun – PMD

Hook	TMC 100, #16-20
Thread	Uni-thread Yellow 8/0
Body	PMD Superfine
Thorax	PMD Superfine
Tail	Light Dun Spade Hackle Fibers
Wing	Medium Dun Turkey Flat
Hackle	Light Dun Hackle

Thorax Dun – Trico

Hook	TMC 100, #18-22
Thread	Uni-thread Black 8/0
Body	Black Superfine
Thorax	Black Superfine
Tail	Light Dun Microfibbetts
Wing	White Turkey Flat
Hackle	Grizzly Hackle

Thorax Dun – Mahogany

Hook	TMC 100, #16-18
Thread	Uni-thread Brown 8/0
Body	Mahogany Brown Superfine
Thorax	Mahogany Brown Superfine
Tail	Medium Dun Spade Hackle Fibers
Wing	Dark Dun Turkey Flat
Hackle	Medium Dun Hackle

Thorax Dun – Callibaetis

Hook	TMC 100, #14-18
Thread	Uni-thread Tan 8/0
Body	Callibaetis Superfine
Thorax	Callibaetis Superfine
Tail	Grizzly Spade Hackle fibers
Wing	Natural Partridge Feather clump
Hackle	Grizzly

Gray Thorax Dun

Hook	TMC 100, #14-18
Thread	Uni-thread Black 8/0
Body	Gray Turkey Biot
Thorax	Gray Olive Superfine
Tail	Moose Mane Hair
Wing	Natural Teal Flank Fibers, upright divided
Hackle	Grizzly Hackle