The soft, downy feathers found around the preen gland of various duck species, such as the mallard, make a near perfect material for the wings of many fly imitations and few more so than those of the Mayfly dun Ephemera danica. These feathers are better known under the French name, cul-de-canard, or CDC for short. Because they are taken from close to the bird’s preen gland, in their natural state they are well impregnated with the oil that the bird uses to waterproof its plumage.
In the CDC Mayfly pattern, a simple pair of natural grey CDC feathers are used for the wings. While it is now possible to purchase dyed CDC feathers in a range of colours, the plain grey seems just as effective as pale yellow, for instance, even though the latter is closer to the colour of the natural.
When placed back-to-back and positioned sloping back over the body, the wing looks very natural. However, choice of feather is important and ideally you should choose the largest available with plenty of soft fibres to give the finished wing the correct density.
Otherwise the CDC Mayfly is tied in a standard dry-fly style. The only minor deviation is that the hackle is applied in open turns over the thorax rather than as a dense ruff. This “thorax-tie”, as it is known, produces a sparser effect and gives a more natural footprint on the water’s surface while still being ample to keep the fly floating.
Size 8-10 medium weight dry-fly
A few fibres of deer hair or moose mane
Stout brown thread
Natural grey CDC
Grizzle cock hackle
1. Catch in the thread at the eye and run it in touching turns to a point opposite the barb. Secure in the small bunch of deer hair fibres which will form the tail.
2. Bind down the butts of the deer hair and catch in a length of stout brown thread.
3. Remove the unwanted stout thread. Now wax the tying thread and dub on the body material.
4. Start to form the body with touching turns of the dubbed thread.
5. Complete the body and rib it with the stout brown thread. Imitate the broader bands found near the tail by making three or four closely tied turns.
6. Complete the body and select a pair of
matching CDC plumes.
7. Secure the CDC wing with several tight turns of thread.
8. Trim away the butt ends of the CDC feathers.
9. Fix the wing into an upright position with the tying thread and secure a well-marked grizzle cock hackle behind the wing.
10. Dub on a little more of the body material and form a small thorax.
11. Tie off the dubbed thread and wind the grizzle cock hackle through the thorax.
12. Secure the hackle and trim. Form a small head and cast off the thread with a whip finish. Trimming away the fibres from beneath the body helps the fly sit low down in the surface film.
WHERE, WHEN & HOW TO FISH
W H E R E
The CDC Mayfly works on any of the rivers that support a population of the natural insect. These can be either chalkstreams or rainfed rivers.
W H E N
Though small, sporadic hatches of Mayfly can appear throughout the summer, it is the period from late May through to early June when the Mayfly hatch is at its peak and a pattern such as the CDC Mayfly most effective.
H O W
Invariably it is fished as a single fly on a floating line and a tapered leader. Classically, it is fished during a hatch of the naturals to trout or grayling that have been spotted actively feeding at the surface.
T Y I N G T I P
When tying a thorax hackle it may be improved further by clipping away the fibres beneath the hook. The hackle fibres sticking out at the sides act as outriggers, supporting the fly on the surface.