Iron Blue Duns

Iron Blue

Baetis muticus commonly known as the Iron Blue is regularly seen between April and October. As a nymph the Iron Blue has 7 plate like gills but the first pair of gills is very small and often overlooked in mature nymphs. The nymphs live chiefly in riffle sections of rivers and streams often found in sand, gravel or mud on the bed of the water. There are two generations per year, firstly the over wintering generation which grows slowly then a faster growing summer generation. This spread of nymphs accounts for its emergence April to October. Great flies to use are the Iron Blue Dun Nymph or Snipe & Purple Spiders

As an adult the Iron Blue can be distinguished from other Baetidae by the presence of 3 veins on the oval hind wing, the second of which is forked. The third vein runs along the lower edge of the wing and is missing in Baetis Niger (Southern Iron Blue)  and Baetis digitalus (Scarce Iron Blue). Of course while fly fishing we do not need to get to this level of detail. The Iron Blue Dun has a very dark olive body with dark grey wings, it has two tails and is about 1/4" long (6 to 7mm). The Iron Blue Dun can hatch all day on rivers throughout the UK. A good imitation is the traditional Iron Blue Dun pattern very popular on chalk streams throughout the UK, ideally a size 14 is a good match to this although flies down as small as 18 can be successful. 

 

While the adults hatch takes place in the daytime vast swarms of male Iron Blue's can be found until dusk falls. Once mated the female flies onto the river landing on a stone, folds her wings and then lays 3,500 eggs along side each other or alternatively descending to the surface releasing the eggs in batches by dipping her abdomen into the water surface. She will climb back once completed but more often she will be weak and drift away in the current, a good time to use a Iron Blue Dun Wet Fly.

The spinner form is commonly known as the Little Claret Spinner. The Iron Blue in its spinner stage now has a red-brown body and clear wings. This is certainly a fly to try.

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