Alexandra
As a couple of people asked here is a version of the Alexandra using Indian blue peacock metallic green "sword" for the wings;
Once again these are just random fishing flies from one of my boxes.
Hook: 12 to 6
Tail: Red ibis, ( sub red goose or similar)
Body: Flat silver, ribbed oval silver or silver wire.
Hackle: Natural Black hen
Wing: Peacock sword fibres ( four to six fibres, depending on fly size from "left" sword, and the same from "right") The "swords" are found at the edges of the peacock's tail fan.
Cheeks: Jungle Cock
On many versions "sides" ( like the "cheeks" but the full length of the wing, of red ibis were added instead of, or as well as the Jungle cock)
The metallic sheen and colour of these feathers is caused mainly by an optical interference phenomenon (Bragg reflection) based on (nearly) periodic nanostructures found in the barbules of the feathers.
Different colours correspond to different length scales of the periodic structures. For brown feathers, a mixture of red and blue is required: one colour is created by the periodic structure, and the other is a created by a Fabry-Perot interference peak from reflections off the outermost and innermost boundaries of the periodic structure.
Such interference-based structural colour is especially important in producing the peacock's iridescent hues (which shimmer and change with viewing angle), since interference effects depend upon the angle of light, unlike chemical pigments.
This however means that these feathers look a lot different in water. "Ordinary" peacock herl often simply looks black under water. How the fish perceive these things is as yet unknown.
TL
MC
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