Here is the fly pattern sheet for the Mercury Midge.

Mercury Midge |

 Here is the fly before adding UV Resin, using Uni 8/0 thread

Mercury Midge - Black |

And the Peacock Blue UTC 70 denier thread (notice how smooth the body is). 

Mercury Midge - Peacock Blue |

 And now coated with UV Resin. Notice how the color changes.

Mercury Midge - Peacock Blue |
Mercury Midge Materials |



Dai Riki 135 or TMC 2487, #18 – 20 scud hook


Extra small Spirit River Hi-Lite silver-lined bead


8/0 or 70 denier UTC black, olive brown, light cahill, peacock blue


Small copper wire (optional: silver and white wire)


Flashback of medium pearl Mirage opal tinsel


  1. Pinch barb and place bead on hook.
  2. Start thread, then attach a short piece of copper wire as rib.
  3. Wrap thread over wire down to the hook bend and wrap thread back to the bead. Keep the body slender!
  4. Palmer the wire rib forward (four to five times).
  5. Make a small thorax behind the bead and whip finish.

Optional: Coat the fly with Sally Hansen’s Hard as Nails or UV Resin

“In past COF Fly of the Month articles, I have discussed the virtues of the Miracle Midge and the Deep Blue Poison Tung. The Mercury Midge rounds out the three subsurface midge patterns you need to successfully fish on tailwaters such as the Crooked River. I fished these three patterns almost exclusively this year on the Crooked and caught hundreds of redbands and mountain whitefish. The Mercury Midge is the creation of Pat Dorsey, noted fly angler on the tough tailwaters of the Front Range rivers of Colorado. I tie this pattern in one size – size 18. Most of the time I use the black version (black thread and copper wire rib). However, I also tie it with peacock blue thread and copper wire rib. The photo shows a silver wire rib and that also works well. I also use a version that has small white (not silver) wire, and that version works well, especially with dark brown thread. I also tie a flashback version that works well during the irrigation season when the water is a little off color. Like Pat Dorsey, I find myself using the flashback version the most. As you can see, this pattern is a very versatile fly.

I fish this fly in combination with either the Miracle Midge (the UV blue version) or the Deep Blue Poison Tung. When the Blue Wing Olives (BWOs) and Pale Morning Duns (PMDs) are hatching, I will use a size 18 (BWOs) or size 16 (PMDs) Mercury Pheasant Tail (another Pat Dorsey pattern) as my bottom fly. When the hatch is in full swing, I move my pheasant tail to my top fly.

If you tie flies, I highly recommend that you purchase Pat Dorsey’s Tying and Fishing Tailwater Flies. It is a little pricey, but the patterns he provides and his knowledge on how to fish the patterns will easily provide a big payoff with big fish days.” – Bill Seitz

Lastly, here is a black version with the optional Mirage Opal flash.

Mercury Midge - Black |

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