For the most part the Small Spurwing Centroptilum luteolum is a mayfly of rivers and streams. This upwinged fly is also found in some large lakes that have wind-sweptshallow gravelly margins, particularly in Scotland, where its distribution on rivers is reported to be rather more locallised than it is further south.
The Small Spurwing is fairly common and widespread in Britain and Ireland and occurs throughout most of mainland Europe.
The common name Small Spurwing reflects the fact that this is the smaller of two species found in Britain and Ireland that have tiny narrow hindwings each bearing a sharply pointed outcrop - a spur. You will need an eyeglass to see this featurev clearly, but of course it is not necessary to include such detail when tying artificial flies. (As if we could!)
The nymphs of Centroptilum bifidum are to be found mainly in the glides and pool margins of rivers and streams and in the wind-swept margins of some large lakes. Small Spurwing nymphs are agile darters. When a dun is ready to emerge the nymph swims up to the surface (rather than emerging via partly-submerged vegetation or rocks.
A size 16 or 18 slim-bodied olive-coloured artificial nymph fished in the surface film works well when Small Spurwings are hatching. When there is no hatch a weighted nymph such as a bead-headed Gold-ribbed Hare's Ear is likely to be necessary to get down to where the trout are feeding.
As always when flyfishing on food-rich waters, matching the hatch can make a big difference, but it's not merely a matter of making your fly the right size, colour and shape so that it looks like the insect you are trying to imitate. Most important of all, you need to make your fly behave like the natural insect. This is a subject I cover in detail in Matching the Hatch, and in my experience behaviour is the most important topic in flyfishing. Put simply, to be a really good flyfisher you need to know how aquatic insects behave, how trout behave, and how you need to behave in order to make your fly behave like a credible insect... and without scaring the fish!
The Small Spurwing Dun hatches generally in sparse trickles rather than dense flushes, but if there is nothing else hatching then it may be advantageous to use a reasonably close imitation.
A good general imitation for all sorts of olive duns including the Small Spurwing dun is that old favourite, Greenwell's Glory. A Rough Olive can be equally effective, I find.
Of course, a lot depends on how windy the weather is, because without a surface riffle the fishing can be very tough indeed, especially on bright summer days. That is when a closer imitation of the Small Spurwing dun really can be all the difference between success and failure.
You won't need to differentiate between male and female duns when choosing an artificial fly to match the hatch when Small Spurwings are about in good numbers, but if you would like to be able to tell males from females it's very easy: just look them straight in the eye.
Male duns (and indeed spinners too) of the Small Spurwing mayfly, in common with several other closely related up-winged flies, have what are termed 'turbinate' (turban-shaped) eyes. Having these specially adapted eyes is thought to help male (at the spinner stage, actually) to locate females that are not yet paired with another male in a swarm. It seems to work, because these and other related mayfies seem to be suffering less than many from the many pressures affecting riverfly populations in Britain and Ireland.
Males spinners swarm just above the surface of the water from late morning through to dusk. Having mated, a female will fly upstream and then release her eggs in a single batch by dipping the tip of her abdomen onto the surface. Because there are usually two generations of adult Small Spurwings each year one in the spring, and a second in summer adults can usually be seen from April right through to the end of the river trout-fishing season and often beyond in to November.
A Tups Indispensable is a pretty good representation of the egg-laying spinner, and a size 18 is about right to match the size of this relatively small mayfly. Spent spinners, on the other hand, deserve a closer imitation, because trout have more time to inspect them. A spent-wing tying style is much better than a hackled fly.
In my book Matching the Hatch, which I wrote for flyfishers of all abilities, there is plenty for experienced anglers as well as newcomers to the sport. There you will find large pictures and tying details for some superb patterns (a few are my own but most have been contributed by the world's top flyfishers including Charles Jardine, Brian Clarke, Bernard Venables, Jon Beer and many others. There are some very good matches for both duns and spinners, artificial flies that have been proven to give great results, especially on days when the fishing is tough. It is all written in jargon-free plain language that won't give a beginner a headache.