Alainites muticus L. - Iron Blue

Phylum: Arthropoda - Class: Insecta - Order: Ephemeroptera - Family: Baetidae

Nymph of Alainites muticus, the Iron Blue

Note: This species was formerly included in the genus Baetis, although strictly the genus name is Baëtis, but as people searching for information on the internet do not generally include accents (diacritical marks) such as the umlaut accent above the character ë, we have used the easier-to-type Baetis in the main text of this page.

Alainites muticus goes by the common name of the Iron Blue. This common name is used by anglers to include at least three very similar species, which are described briefly later in this page.

A slim Pheasant-tail Nymph

The Iron Blue nymph is a slim agile darter with seven pairs of gills. It is characterised by a central tail much shorter than the two outer tails, and there is no dark band half-way down the tails, as there is with nymphs of the Pale Watery, Medium Olive and Small Dark Olive.

Imitating the nymph

The most important feature to imitate if you want to catch trout while nymphing is the behaviour of the natural insect. Sinking the rod tip just below the water is a great help if you want to impart short, jerky movements to your nymph as it drifts downstream towards you. In very fast water the turbulence of the current is generally sufficient to create the illusion of life; that's helpful, because it's enough of a challenge just to retrieve line fast enough to keep in touch with your nymph. Try a weighted Pheasant-tail Nymph when there is no hatch and the fish are lying deep, and a Gold-ribbed Hare's Ear when the hatch is just starting.

Iron Blue Dun (male)

Dun or subimago

Iron Blue duns can be seen on all kinds of flowing water, including chalkstreams, acid spate rivers and fast-flowing brooks. This is a tiny fly compared with other up-winged flies of springtime, and its main emergence period is April and May. A second generation has its peak emergence in September and October, but usually the numbers are much reduced compared with the hatches of springtime.

Often referred to as a fly of bad weather, because even on cold wet days the duns hatch and can give good sport when little else is on the water, the Iron Blue dun emerges at the surface in open water. Hatches can be fairly dense even on sunny spring days, and the duns are generally on the water from late morning until 'tea time' - about 4pm in April but an hour or so later in May.

Specific imitations have been devised, but a general pattern is usually acceptable in the rough and tumble of a high-water spring river.

Iron Blue Dun, devised by Pat Russell

Iron Blue devised by Pat Russel

Male and female duns are very similar in appearance. Distinguishing features are the eyes - large and brown in males but smaller and more yellow in females. Males have claspers appended to their penultimate body segment, but of course females do not have this feature. The same artificial pattern serves perfectly well as an imitation of both male and female Iron Blue dun.

Spinner or imago

Iron blue spinners lays their eggs in the afternoon, and so they are useful flies to imitate. The differences between the sexes are quite marked. The female is sometimes called the Little Claret Spinner, while the male is known as the Jenny Spinner. (Insects have no say in the names they are given: male Ladybirds and male Damselflies for example have to put up with effeminate names too!) The males swarm during the afternoon, but they don't hang around once it begins getting dark.

Iron Blue Dun, devised by Pat Russell

Female spinner

While the wings of both male and female spinner are transparent and shine brilliantly when sunlight catches them, the bodies could hardly be more different. Females have dark claret-brown bodies with pale segment rings, while male spinners have bodies which are translucent white except for the last three segments, which are orange-brown. The tails of both male and female spinner are pale grey.

Like other members of the family Baetidae, Iron Blue spinners are reported as usually crawling down plant stems, bridge pilings or semi-submerged rocks to lay their eggs under water. In such cases the main opportunity for trout to take them from the surface of the water would be as they return to the surface after laying their eggs, when in most cases they would be swept away on the current, there to die and become a spent spinner (if fish haven't risen to make their brief adult lives even shorter). An artificial spent spinner pattern seems a wise choice, therefore.

Iron Blue Spinner (female)

Male spinner

That is not the only way that Iron Blues lay their eggs. They also fly over the surface of a river, generally heading slowly upstream as do other up-winged flies, and dipping the tip of the abdomen into the water so that the ovipositor can release batches of eggs below the surface.

This is the classic egg-laying spinner behaviour that is best imitated using a hackled artificial spinner such as Tups Indispensable or a Houghton Ruby (a pattern devised by riverkeeper William Lunn on the River Test). The latter is a beautiful dry fly, and it shows up very well when evening sunlight falls on it. A size 16 is quite big enough for copying the Iron Blue, and if your tying skills and your eyesight when fishing are up to it then a size 18 is even better.

Oh, if only we had more Iron Blues (they are becoming increasingly scarce on many rivers where they were once abundant) and more sunlit spring afternoons where a Houghton Ruby could shine (in every sense)!

Iron Blue, parachute tying

Iron Blue with parachute hackle

Similar species

Nigrobaetis niger (formerly classified as Baetis niger) is sometimes given the name Southern Iron Blue. It is much less common than Alainites muticus and its occurrence is rather more localised.

Nigrobaetis digitalis, referred to as the Scarce Iron Blue, is even more localised in its distribution in Britain.

Like Alainites muticus, these flies emerge from slim agile-darter nymphs that spend most of their time in weedy riffles. At the dun and spinner stages there are minor differences in wing venation between these three up-winged flies, but nothing a trout could notice. Therefore, from an angling point of view Alainites muticus, Nigrobaetis niger and Nigrobaetis digitalis can all be considered as Iron Blues; artificial flies and tactics that work for one will work for all.


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