Bob Wyatt shows how and why he came to tie his ‘sitting duck’ – the Deer-Hair Emerger.

Hook: Kamasan B-100, or similar light wire, curved shank emerger style hook.
Wing: Medium to fine deer hair. Colour and shade according to naturals and light conditions (white or black for hi-viz versions).
Abdomen: Natural fur; fine underfur for ephemerids, bulky hare’s mask and/or seal’s fur for sedge pupae. Colour mix as appropriate.
Rib: Tying thread tag.
Thorax: Spiky hare’s mask.
*Important tips: This fly usually requires floatant, such as Gink, especially in fast water. For the DHE to fish correctly, apply floatant only to wing and thorax, avoiding the abdomen and hook, which must sink. Watch the proportions of the wing when tying. The hook will normally keel the fly, but a wing which is too tall might topple it on to its side, especially if the abdomen is of a bulky buoyant material, or you get floatant on to the hook and abdomen. For better flotation in fast water, flare the deer hair Compara-Dun style.

1. Tie in a bunch of fine to medium deer hair, well back from the eye of the hook. Wrap down the hair butts and take thread around the hook bend, leaving a long tag of thread for the rib.
2. Dub tying thread and wrap to wing. Bring tag end up in a counter-wrapped rib, tied in ahead of wing.
3. Take tying thread to hook eye and dub with spiky hare’s mask. Wind dubbing back to wing base, forcing wing into upright attitude, then return to eye with two turns through dubbing – binding and flaring the hare’s fibres. Whip finish.

The Deer-hair Emerger proves irresistible for a good Sutherland trout. The Deer-Hair Emerger proves irresistible for a good Sutherland trout.

Al Caucci says, with regard to just what it is that makes a fly appear vulnerable and what makes his Compara-Dun and Compara-Emerger so effective, that it is simply the lack of a hackle. Ogden’s great old Gold Ribbed Hare’s Ear is the prototype of the modern no-hackle dry fly. Carl Richards and Doug Swisher based their ground-breaking concept of fly design on this essential feature; the same feature that Fran Betters exploits in his Haystack series. Caucci based his Compara-Dun on Betters’ Haystack, which had been fooling the Au Sable trout for decades.

In To Rise a Trout, Britain’s John Roberts is quite dismissive of Al Caucci’s Compara-Dun, and believes that it does not give an adequate impression of a floating dun’s body, and none of the leg signature, what he calls its ‘footprint’, in the surface. Roberts admits it catches trout, but, he says, so would a cigarette butt. A tad harsh, you might think; you could easily apply the cigarette butt objection to any design, and I believe Roberts has maybe missed the point here – and, for that matter, so has Caucci. In The Trout and the Fly, Clarke and Goddard establish that the trout does not see much of the natural fly that rides on the surface, except for the tips of the upright wing as it enters the trout’s ‘window’ and the impression of the legs in the surface film. They designed their Upside Down Paradun to avoid having the hook penetrate the surface. It’s a good idea in theory, and no doubt catches fish, but some of their conclusions are maybe open to question.

If the only parts of a dry fly that are visible to a trout are the wing-tips, and anything that penetrates the surface, and there is no reason to believe otherwise, it seems to me that more thought should be given to exploiting these two aspects, rather than fighting with the hook’s tendency to penetrate the surface. Clarke and Goddard are right in their analysis of how most ‘dry’ flies are actually presented – usually hook-down and penetrating the surface. I’d argue that surface penetration is precisely why most conventional dry flies work at all. In other words, most of the time your orthodox dry fly is fishing like an emerger. To my mind, then, the theory behind Clarke and Goddard’s approach in The Trout and the Fly, and the design of their Upside Down Paradun, is going in the wrong direction.

I’ve found the Compara-Dun to be an excellent fish catcher, but like John Roberts, I think it is also a poor representation of a dun. For that matter, so are all collar-hackled dry flies. Where I think we are missing some wood for the trees is in our attempt to represent the ‘footprint’ of a fully emerged dun, whereas Caucci and Swisher and Richards are concerned with the helpless insect. The perfect dun is by no means helpless, and, to the extent that they learn, trout soon learn to focus on the emerger and the stillborn dun. It’s not that trout don’t take the duns – they obviously do – it’s just that they will ‘select’ the imperfect and helpless insect if it’s available. In fact, I’ve watched trout ignore so many fully emerged duns that I’ve come to question just how often they actually do eat them.

To develop a working scheme for fly fishing, it is not necessary to have all the answers as to ‘why’ a trout takes a fly, but is important to have a few rules of thumb. My rule of thumb for surface trout flies is that trout probably don’t take dry flies because they mimic accurately the form, or footprint, of the perfect insect, but precisely because they don’t. I’d argue that the reason traditional hackled dry flies work at all is because they don’t look anything like the perfect dun, but probably like incomplete or damaged insects. Take the Grey Duster, for example, one of the most reliable patterns in a Mayfly hatch, and one that many anglers reach for when the trout start to rise. Courtney Williams regarded it as better than any specific Mayfly imitation. The posture of a tailless Grey Duster is such that the body is awash, usually penetrating the surface – like an emerger. It is in its lack of resemblance to the fully emerged dun that its attraction lies, not the converse. Why then, try to imitate the footprint of the perfect dun when the hook makes it so difficult to get the fly to adopt the correct posture?

When you compare a traditional Halfordian dry fly to the natural, it’s clear that, among a raft of naturals, the orthodox hackled dry fly stands out like a goose in a hen house. That, for me, answers the old mystery of why a trout will select your fly from among hundreds of perfectly good naturals, and I see no other reasonable explanation. It certainly can’t be the case that your nice Red Quill looks more like a natural than the naturals, right? It must be that, within certain parameters, the trout will accept a variety of things that look ‘good enough to eat’, and for the best of reasons – necessity. Despite what we like to believe about the intelligence of our quarry, when a trout rejects a fly, it is not out of suspicion, but lack of recognition. As Brian Clarke has said, a trout doesn’t reason, it simply recognises a fly as food or not. When a trout is being ‘selective’, it has really just switched off its recognition of anything that is out of context.

I reckon that old Halford’s orthodox dry fly just looks to a trout enough like food worth going for. Because an insect on the water takes a variety of forms, the trout has to respond to anything insect-like that looks like it belongs to the prevailing hatch – and vulnerable. A fly that presents, say, three essential aspects – size, shape, and posture – is likely to be eaten, as long as it looks helpless. For the trout to recognise it as food, presentation of the fly also has to mimic the behaviour of the natural. If you think about it, seeing your steak suddenly start moving off your plate would certainly make you hesitate (er, bill please, waiter!).

Apart from being a good catcher of fish, the best thing about the Compara-Dun is its simplicity and ruggedness. The flared deer hair wing is very easy to tie, unlike carefully setting those little wing-slips on Swisher and Richards’ thorax-style designs. Not only that, if not perfectly positioned, those beautifully shaped but fragile feather wings can be quite nasty to cast, causing some terrific twisting of a light tippet. The Compara-Dun occupies a sort of middle ground between emerger and dun, and is a reasonable representation of a ‘stillborn’ dun, a fly that has only partially escaped the nymphal shuck – one of the most vulnerable and irresistible of the prey available to trout. The way the Compara-Dun’s wide spread tails support the body on the surface is probably more appropriate to a spinner imitation, and it is therefore a reliable choice in a rise to a fall of spent fly. Riding smack in the surface film like that, it looks like it isn’t going anywhere. The Compara-Dun can be improved by taking its vulnerability aspect a bit further, by getting that abdomen to penetrate the surface. For one thing, the sunk abdomen enables the trout to see it from further off; for another, it presents the aspect of an insect in one of its two most vulnerable forms – the emerger.

The design of trout flies, rather than variations in patterns, has not been a concern of fly tyers for really that long. Halford, definitely a colour and pattern guy, is certainly responsible for the dry fly hackle fetish, which by now has become a multi-million chicken industry. Halford simply varied the hues of hackles and bodies on his rigidly standardised dry fly design, to the extent that he ultimately relegated even that great trout catcher, the Gold-ribbed Hare’s Ear, to non-U status because it didn’t have a nice stiff hackle. Two of the most reliable flies for an ephemerid hatch, it seems, are the Hare’s Ear and the Grey Duster, neither of which resemble a complete dun.

During the 1970s, some good anglers, and in some cases teams of good anglers, started thinking about the design of flies rather than pattern; Marinaro, Swisher and Richard’s, Clarke and Goddard, Caucci and Nastasi, and Gary La Fontaine stand out as innovative dry fly designers. One of the best accounts of this whole approach to fly design as opposed to pattern is Datus Proper’s excellent and entertaining What the Trout Said. The main thing these guys have in common is their concern with form rather than colour or other magical properties. In other words, an approach based on observation and reason, rather than convention and art. We have to decide what looks good in a trout fly. What looks good to us should be what looks good to a trout: an insect of the appropriate size, shape, and posture that can’t fly away.