Lockdown Fly Tying Day #19

This is a direct excerpt from my book “Guide Flies”, not only is it the story of an exceptional stillwater pattern, particularly for the bank angler, but equally a tale of the evolution of a pattern and the processes which took a basic fly from something of a concept to a simple and functional pattern over time.

The quick sink Corixa:
I first read about Corixa in Brian Clarke’s book “In Pursuit of Stillwater Trout”, a wonderful introduction to logical Stillwater bank fishing and recommended if you can get your hands on a copy. I can’t say that I took a whole lot of notice of this particular bug at the time, I had never seen a corixa and I seemed to catching enough trout on midges and hare’s ear nymphs to really worry about it.

Brian Clarke’s book ” In Pursuit of Stillwater Trout” has probably had a greater impact on my stillwater fishing than anything else I have read. A simple approach based on understanding and trying to copy real trout food items. The corixa pattern in the book isn’t what I would consider a great one, but the seeds for experimentation were planted.

I should digress for a moment and say that Corixa and Backswimmers are technically different, but they have very similar behaviours and profiles such that from a fly tying perspective you can pretty much treat them as the same, although this might annoy the biologists a bit.

Backswimmers in the water orientate themselves upside down when swimming, that said, from an angling perspective they are so similar to corixa that one doesn’t really need a separate pattern.

Corixa are aquatic beetles, of the family Corixidae, they don’t breath through gills as do mayfly nymphs, damselfly nymphs, dragonfly nymphs etc. but have to come up to the surface for air, remarkably they can also fly and do so on occasion to locate a partner and mate generally in large swarms. When they surface they trap the air in hairs around their bodies and carry it around with them rather like a miniature aqualung. They are of interest to anglers for a number of reasons:

Firstly they are found in an awful lot of waters that are also inhabited by trout.

Secondly they are there all year around and there is no messing about with pupal, nymphal, larval and other stages as with so much other trout food, which should at least make them easy to copy.

Corixa have no pupal, nymphal or other stages to concern the angler and if they are present in a water they are present all the time, something worth knowing if you are choosing a suitable pattern to start off with on a new water.

Pretty much there are just little corixa and bigger ones, although they don’t actually attain any really great size.

Thirdly, except when they are undergoing some mating flight they tend to occur somewhat randomly and as a result represent a rather opportunistic snack for the average Stillwater trout, you don’t need a “corixa hatch” to make good use of a suitable imitation.
Added to all of that, the corixa’s lifestyle make them a rather good target for trout and equally a good insect for bank anglers to imitate. Given their need to leave their weedy homes for a breath on a regular basis they put themselves at risk of detection and consumption all day long. When you imagine that a mayfly nymph only has to rise to the surface once in its lifetime, the poor corixa has to do this over and over again every single day.

Plus, because of the need for air and the swim required to fetch some they tend to inhabit relatively shallow water, well within the casting range of the average fly fisherman, which if you are an angler is a very fortunate happenstance.
The true importance of this humble little, if rather extraordinary, bug was brought home to me years ago when I had access to some spectacular fishing on private club water in the Kouebokkeveld a few hours drive from my home in Cape Town.

The area is arid, high and frigid (The name in Afrikaans means “Cold Buck Land” in direct translation). The small to medium sized dams, which are used by the farmers for irrigation of some of the most productive soft fruit orchards in the world, make excellent trout habitat in a country where a lot of the water is just too warm.
These dams regularly produced, from simple fingerling stockings, some absolutely astounding growth and trout up to ten pounds were hardly out of the ordinary, the waters were also for the most part clear and weedy, ideal habitat for both fish and fishermen.

A corixa underwater, the tell tale shimmer of the trapped air around its body can be clearly seen.

Although most of these lakes sported populations of corixa, one in particular, and a favourite of mine, was absolutely filled to the brim with the little bugs. In fact it was almost impossible to put your hand in to pick up a sip to drink on a hot day without taking in more protein than you had bargained for. It became apparent over time that the trout tended to come into the shallows to feed, either early morning or late evening, when the light levels made them feel safer. They would on occasion do the same if there was a good riffle on the surface, one imagines for the same reason that they felt less vulnerable under those conditions.

When I first seriously started experimenting with corixa patterns most South African stillwater anglers were predominantly using large lures or general attractor patterns.

At the time most anglers were fishing woolly buggers or perhaps damselfly and hare’s ear nymphs, many on sinking lines. Having come from a different background fishing in the waters of the UK I had a somewhat alternative approach to bank fishing and didn’t even own a sinking line at the time. I preferred to fish a long leader and a single fly with a floating fly line that I could use to detect the takes of fish that were subtle when retrieving slowly.

Standing in the shallows fishing damsels and hare’s ears I came to think that the fish must eat the corixa, and although we rarely killed a fish when we did so it proved that they were stuffed to the gills with these little beetles. So much so that gutting a recently captured trout would on autopsy reveal something akin to a corixa sausage, with decomposing bodies at one end and still wriggling ones at the other. There were just so many of these bugs about that I seriously wondered if the trout had to feed for more than a few hours a day before they were left groaning on the bottom of the lake with indigestion. Certainly there were frequently very quiet spells in the fishing during midday.

Another image of a subsurface corixa clearly showing the “aqualung” of air trapped around its body.

So I set about testing some imitations of corixa, they are simple on the one hand but tricky to get quite right on the other. Trying to imitate the flattened and rounded body of the natural can easily result in too much material on a small hook. Most of the corixa found in this dam were no larger than a size 14. The key triggers it would seem are the silver bubble of air around the body of the insect, the flattened shape and the two paddles with which they propel themselves through the water. I am a great believer in trying to capture the key points of an insect when designing an artificial, a sort of caricature as it were of the real thing.

There were a lot of corixa patterns around at the time, some seemed better than others but to my mind they were never quite right. Many sported hackles as imitation of the legs, but corixa legs are quite pronounced and fine fibres of a hackle didn’t really seem to look right to my eye. Then other patterns of the day had two distinct legs manufactured out of one thing or another, the problem was that they were tied in separately, making for an additional operation at the vice and taking up more space than there really was available on the hook.

Using fibres from the back removes the need or adding additional materials and thus bulk of the fly. In my pattern I use two fibres glued together for each leg.

Eventually over a season or so of experimentation the “Quick Sink Corixa” evolved. Although on occasion we wanted a fly that didn’t sink too much for the most we wanted a pattern that would get down, at least a bit. The use of lead wire on the shank solved that problem but was the wrong shape and closed the gape of the hooks. By flattening the wire we suddenly solved the problem of the weight and the shape at the same time. This brought with it another problem however; traditionally one used flat silver mylar to imitate the reflective qualities of the air bubble around the body.

It certainly looked the part but it was terribly difficult to wrap flat mylar around the now squashed lead underbody. Eventually though we found that using a small bunch of silver or pearl crystal flash made wrapping the body much easier, even more so if you anointed the lead with a spot of super glue before you wound it on. The final revelation, and perhaps the most significant in this pattern was using pheasant tail fibres for the shell back, not that that is particularly unusual, but we realised that we could use the same material for the legs. Separating out two fibres on either side, after forming the back, we could cut out the excess and have neat legs, perfectly positioned on either side of the fly without any additional bulk and leaving space for a neat whip finish.

Of course this didn’t all happen overnight, we manufactured some good and some pretty dreadful and time consuming corixa imitations, I think that they all worked, but this pattern was the culmination of experiments and adjustments which have now resulted in a quick to tie, neat, inexpensive and very productive Stillwater fly.

There was one further discovery about this pattern, I try to use ring eyed hooks for many imitative Stillwater patterns, if you don’t your lovingly created imitation of a damsel fly for example flips upside down every time you retrieve. Because we were fishing the corixa in such clear water we were able to observe the behaviour of the fly and noticed something very interesting. With each retrieve the fly would flip upside down for a moment, but it seemed that where the corixa is concerned this is a good thing. The fly on each slow strip gives a little semaphore flash of its underside, a little winking beacon that seemed to pull the trout in from yards away. So now the corixa is the one fly that I always tie on a down eyed hook, it just seems to enhance the effectiveness of the pattern a little bit.

Whilst for many patterns the fact that down-eyed hooks flip the fly over may be a disadvantage, in this corixa pattern it is a definite plus. Adding a little blink of flash on each retrieve, often pulling in fish from some distance.

 

Tying the Quick Sink Corixa:

 

This post and the fly described comes from my book “Guide Flies” if you would like to purchase a downloadable copy of it or my other book “Essential Fly Tying Techniques” you will find both links and discount codes below. The discount code will let you purchase the book at a 50% discount during lock down.

Discount code Essential Fly Tying Techniques: DR62J Code will expire 17 April 2020

Discount code Guide Flies : SB94S Code will expire 17 April 2020

Thanks for reading, stay safe out there.

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2 Responses to “Lockdown Fly Tying Day #19”

  1. Graham Avery Says:

    Thanks Tim.
    I remember catching two nice fish with corixas under your direction during a Lucano morning rise. You then also slayed them in the evening with a semi-floating version with an ostrich herl underbody

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