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TMC 900BL (or similar dry fly hook), sizes 16-22


Olive 8/0


Olive or olive-brown fine synthetic dubbing


Blue dun turkey flat


Four to ten blue dun hackle fibers


Blue dun

BWO Thorax Dun

(A Blue Wing Olive Emerger)


Last month we tied the Baetis “emerger.” In October we tied the Baetis nymph. This month we will work on the Baetis adult, sometimes called “Blue Winged Olive” or “BWO” for short.

This version of the BWO is a “thorax” style fly. Thorax flies feature a wing that sits farther back than standard “catskill” style flies.  In the latter, the wing is located at the front 1/3 point on the hook; thorax-style flies feature a single wing mounted at the midpoint of the shank. The wing is constructed in a narrow form when viewed from the front, but wide when viewed from the side.  Thorax-style hackle is spaced throughout the thorax area instead of being densely packed, and a “v” is normally trimmed in the bottom part of the hackle to allow the fly to ride low on the water.

A good explanation of this pattern, its origin, and of the thorax technique, can be found in Randall Kaufmann’s Tying Dry Flies (Revised Edition).

Tying instructions:


1.                 Mount thread just above the back of the barb area.  Build a tiny dubbing ball here.

2.                 Measure four to ten blue dun hackle fibers to the length of the shank, and tie them in just ahead of the dubbing ball.  Split them into two bunches of equal size by bringing thread up between the fibers.

3.                 Move the thread forward to the halfway point on the shank.  Trim out the top center of the stem of a blue dun turkey flat, and strip off all of the short fibers near the bottom of the stem.

4.                 Squeeze the clump together to form a bunched, flat wing, and measure it to the length of the shank. Position it at the midpoint of the hook, or just ahead of that point, and tie it in directly on top of the hook.  Trim the butts at an angle tapering to the rear of the hook, and tie them down.

5.                 Lift the wing while keeping it squeezed between thumb and forefinger, and take a wrap around its base. As you wrap around the base, pull rearward and catch the thread in the remaining stubs of the butts.  That is all that is needed to stand this wing up properly.

6.                 Return the thread to the tail area and dub a slender, tapered abdomen.

7.                 Just behind the wing, tie in a blue dun saddle or neck hackle of proper size.

8.                 Dub a nice thorax behind and in front of the wing, leaving a space behind the hook eye for the head.

9.                 Wrap the hackle in back and in front of the wing.  Six or seven wraps should be enough.  Tie the hackle off and form a nice, small head.


Don your specs so you can see this tiny creature, dress warmly, and see ya on the creek...for some cold winter fishing.


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Copyright 1998 by Granite Bay Flycasters unless otherwise noted.