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A “Dun” is that stage of the life cycle of a Mayfly when it emerges and rests on the surface of the water or nearby vegetation whilst its wings dry. During the Dun stage it is very vulnerable to passing and searching fish.

The Caenis Dun is a generic representation for members of the “Caenidae” family of Mayflies.  The Caenidae family are the miniatures of the Mayfly family and include the smallest of the mayflies. Caenis Duns are often referred to as “the anglers curse” because they are often very small and because the Dun stage of their life cycle is as short as only 20 seconds. When Caenis Duns are emerging they are often mistaken for midges and smut flies. Midges are part of the Chironomidae family of true flies whereas Smut flies are an entirely different species and are in fact “Aquatic Bugs” of the order Hemiptera.

If you have a look at Caenis Duns there are fundamentals of shape that are common across the species and captured by this pattern. The tail consists of only three filaments; the body starts thin and is then cigar shaped with 9 distinct segments. They have 6 legs and wings faces back at about a 60 degree angle. The common colours are gray and brown and when they are hatching the vision is of very small single winged sailing boats on the water.  I generally only carry Caenis Duns in size #16 but if I had eyesight that would allow me to tie smaller versions I would probably also carry size #18 Caenis Duns.

Common names, size and dressings

GREY #14 - #18 Dress as for an Adams.
BROWN #14 - #18 As detailed below.

Materials for Brown Caenis Dun

Process

A	Wind on the thread in touching turns from the eye to the bend of the hook. I have used a Knapek 'wet' fly hook here because the wire on the dry fly hook is just too thin. Understanding hooks Tie in a tail about as long as the hook shank consisting of only three to six Pheasant hackle fibres. Tails on flies Tie in a length of thread for the rib.

B	Dub on a thin cigar shaped body on the back two thirds of the hook shank. Single strand dubbing Wind the ribbing material over the dubbed body to form 4 or 5 body segments. Body segments on flies Tie the ribbing material off and trim.

C	Select a feather slip and tie it in directly in front of the body.

D	Trim the feather slip to length to represent a small wing laying back at around 60 degrees.

E	Tie in the hackle (I like coch-y-bonddu hackle for my brown caenis duns because the black along the quill of the hackle gives the visual effect of extending the body) directly in front of the wings.

F	Pick up the hackle (or hackles) and wind it forward in touching turns to just behind the eye of the hook. Tie the hackle or hackles off and trim the butt end/s. Build up the head, whip finish and varnish.

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