Billy - Did you try a #16 crane fly? I've had this be the answer to several "head-scratching" days on many PA creeks; cranes will hatch sparsley all day long, hanging in the surface film as they drift along, an easy target for sippers; as a clue, you'll find the adults bumbling around in little masses along the shoreline at the water-line on rocks and logs; it looks like the little creeps are rather enjoying themselves, having little cocktail parties or something - but we all know they're sorting through each other for mates.
Pattern idea: I suggest a thin, pale-gray winding silk body, with the rear tied slightly over the bend of the hook and thickened a bit there; tie in an over-sized dark blue dun feather where the hook straightens. Wind thread forward and make a humpy thorax with a wee bit of pale orange thread tie in/wound just at the front; for legs, palmer the blue dun feather - just a few turns - over the fly from back to front - and, nicely, neatness doesn't count here; the hackles can splay any which way - oh, joy!! As an option, you can trim off the top hackle fibers add a very small bunch of pale gray or white antron tied to lay back over the thorax - only about 1/8th inch, though; the pattern seems to work with or without it.
You can treat the fly with floatant and fish it on top, across and down-stream, skittering it a bit if you've seen any naturals buzzing across the surface; this works great working it along the stream's edge. But this pattern really kicks butt after the flies wets and sinks just below surface. Then you can also fish it upstream and let it dead drift just under the surface - right through active feeding lanes. I had a fantastic day on the Clarks with this pattern two seasons back when a lot of other guys were striking out. Now, that was in the spring, but the crane is a season-long entity. On my home water - the Bushkill here in Easton - they were along the stream's edge yesterday in decent numbers, but you couldn't see any out on the stream itself; I took several nice wild browns on this pattern, fished upstream as I've described...maybe cranes are working on Clarks, too. No one can make any promises, but this might be worth a try - good luck.
Incidently, your posting made me yearn a bit for that gin clear Clarks water - think I'll plan a trip out there soon...it's been awhile.
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