I did not recently tie these flies. They are part of a batch tied several years ago. I have always thought this Rosborough fly pattern to be his best creation. I have rarely deviated from the gray body, although you so easily could. I have used different body materials besides the called for Muskrat fur (and guard hairs). This is a good example of a ‘classic’ pattern (at least in the Western U.S.) that has evolved away from natural furs to synthetic components. The tail and dubbed/strung collar are the 
guard hairs from a patch of Muskrat fur. Today, I would opt for the simpler brown hackle barbs of a hen feather for the tail and the collar. The body has been tied with the underfur dubbing of the Muskrat…even today one nice dubbing material. But, again, synthetics are available too..and, I have even used cat (Kudra the Cat) fur with good results, although it does not seem to have the density for larger flies. The very appealing Ostrich Herl at the thorax is a favorite of mine for a wound body (abdomen-gills or thorax-legs) as well as extended tails (The Orb). Research Polly Rosborough or better yet buy his simple little book Fuzzy Nymphs. Don’t discount the information as too simplistic or too old because of the older techniques shown. This Central Oregon legend was a bug stalker. He set the tone for the more sophisticated Rick Hafele and Dave Hughes. (The Complete Book of Western Hatches).
Thread: 6/0 to 8/0 black or red (if weighted shank)
Hook: Size 10-14 (2-3 xl), nymph hook
Tail: Muskrat fur guard hairs or brown hackle barbules
Abdomen: Dubbed Gray Muskrat or alternative synthetic dubbing
Thorax Collar: Muskrat Fur Guard hairs or brown hackle barbs inserted into dubbing loop and wound
Thorax between eye and collar: Black Ostrich Herl
SwittersB & Exploring 
This is one of those flies I used to have ( I enjoy tying it) yet did not use until one day where I caught numerous trout on this gem.
NOW, I never leave home without a few and often use a 12 or 14 as the dropper in a “dry/dropper rig. I have also had luck used instead of buggers in size 10.
Be sure to give them a try!
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Thank you for the recommendation! It is truly a great pattern.
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The recipe you gave calls for an “xl”, sorry for the ignorance, but is that an extra long? Does that make a difference if I only have the long?
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No, not really. It gives you that extra room (length) in a smaller hook rather than going bigger. That particular pattern is often tied in 8’s and 10’s. I prefer it in a 10 and 12. If I had to tie smaller I would go to a longer shank. The materials of Ostrich Herl and the Muskrat guard hairs will tend to force you toward a bigger fly, say size 10. Often you will tie more for what is easiest for you while resulting in a nice looking fly…but, that fly may be limited in use if too big. I like the Casual Dress as a stillwater pattern. Others primarily fish it as originally intended on streams. If I fish it on a lake too large a size is maybe only valuable early in the season when mayfly nymphs are larger. As the season progresses the nymphs seem to be smaller. I imagine you will, if you like this pattern, learn to scale down the materials to match the hook so you can carry it in 10-14.
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I like classic cars and classic flies. These are really very nice! I have had much success using these patterns on most lakes. Pictures are well done…layout and all.
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I love these types of patterns. The fact that it can be tied with locally available muskrat and little else has a lot of appeal – it’s simple and elegant. In a complicated time, when the angler is constantly bombarded with new patterns and new materials, these simple patterns are a comfortable haven.
As I begin to settle into the winter pattern of reading and tying, I often find myself stymied by analysis paralysis, there are just too many choices. It’s tough being a post-modern fly-tyer. Like many of the painters that came after Pollock I find myself looking back. Just as Pollock made anything and everything possible – so too have the modern fly-tyers. So rather than trying to break new-ground I look back to the classics.
Thanks for sharing – I’ll be tying some of these for sure.
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Well said Anthony. As you know, writing a blog eventually provides a self-revelation that much of this has long ago been hashed over…only a new generation or beginner has yet to discover the old, tried and true. The new and innovative is really few and far between and mostly in the realm of manufacturing some rod, reel, fabric or material…but, re fly tying, it soon becomes apparent pattern after pattern is often a spin off of the tried and proven. Out of the copy cats eventually comes a new gem.
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Nice to remember Polly. Hope I live to be 95! Good looking ties.
JB
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Thanks JB…He really did have the most significant impact on my early tying. It was the simplicity, the suggestiveness of his patterns. I also liked how that he was a true naturalist…of the earth if that makes sense. I have written about him before but I saw my little cubicle of Casual Dresses in the fly box and pulled one out to look and marveled yet again, what a great pattern….that pattern always out performed the Hare’s Ear, for me. I would never put a bead on it….I do tire of dubbing the collar though…I must admit to exploring a better-easier technique without forsaking the original too far…not sure that is possible. Sanctity of the pattern is almost laid to the sanctity of the original tier.
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