Slot the 4mm silver tungsten bead onto the ST320 jig hook and start spring olive midge thread behind it.
Run the thread back to the bend and tie in a length of golden stonefly Micro Wormy body material.
Wrap the Micro Wormy forward in touching turns to just behind the bead. Stretch it slightly as you wrap, the translucent material thins down and picks up the olive thread colour beneath it, which is where the olive-brown tone of the finished fly comes from.
Blend natural grey CDC with synthetic spectra dubbing and spin it into a loop, then take two or three turns as a thorax behind the bead. The CDC pulses in the current; the spectra adds the sparkle that stops the fly looking flat.
Pick the thorax out, whip finish behind the bead and fish it as a searching pattern on a Euro rig.
Vary the body colour rather than the shape. The profile is what makes it generic enough to work everywhere.