This is a naturally crippled female Isonychia bicolor dun. One of her main wings came out as a deformed, crumpled yellow object. I found her flopped over on her side struggling on the surface of a small stream.
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Dun: Mayflies have two adult stages. They first emerge from the water as duns (scientifically known as the subimago stage). They then molt into the spinner (imago) stage, in which they mate and die. Sometimes the word "dun" is confusingly used to refer to a brownish gray color in fly tying materials.