Sulfurs should be popping in much of the country, and if you’re casting to especially persnickity trout, you might give this time-tested pattern a try. The thorax-style dry flies that Vincent C. Marinaro wrote about in his 1950 classic A Modern Dry Fly Code are still favorites on the spring creeks of Marinaro’s native Pennsylvania.
Thorax-Style Sulfur Dun
Hook: 1X-long dry-fly hook (e.g. Dai-Riki #300), size 14.
Thread: Yellow, 6/0.
Wings: Matching pair of light-dun hen-back feathers.
Dubbing ball: Yellow beaver dubbing.
Tails: 8-10 stiff light-dun hackle fibers.
Body: Yellow beaver dubbing.
Hackle: Light dun.
Thorax: Yellow beaver dubbing.
Tools: Wing burners.