The following is reprinted from Philip Rowley,s website: Fly Craft Angling with his permission.

A warm breeze, rippled water, overcast skies and the gentle bow of a floating line spells heaven for the fly fisher, especially to the Callibaetis conscious. Cruising confidently under the shroud of the wind textured water trout root out pre emergent Callibaetis nymphs. As the nymphs near maturity they become itchy and active rising and falling above the chara beds through a series of undulations and rests. Absorbing air and gases from the surrounding waters the nymphs take on an enticing sparkle breaking up their usual mottled tan to olive color schemes. Opportunistic trout key on this feature with abandon, nymph patterns with a hint of flash make for memorable days. Choose chironomid skinny, anorexic patterns, as robust nymph patterns are not met with the same relish by selective fish.

Seasoned anglers know the benefits of fishing nymph patterns in Callibaetis rich waters such as those dotted with clear water, chara beds and marl shoals. Although not the dominant food source in stillwaters, mayfly nymphs from species such as Callibaetis do occur in sufficient numbers to spark an interest in trout and anglers alike. Most anglers recognize the characteristic arched posture, fluttering abdominal gills and darting minnow-like motion of these dainty swimming nymphs. On a daily basis the hatching nymphs begin their warm up activities like clockwork as the trout saunter from the depths to gorge themselves on the shoals. Knowing this, positioning throughout the hatch takes on added importance. Parking a cast away from the drop off is winning tactic to intercept prowling trout. Floating lines coupled with leaders 15 feet or longer wind drifted onto the shoals is a primary strategy. As the hatch intensifies cavalier trout spread out in loose schools patrol the shoals. At this time an intermediate line provides an angled retrieve to the boat or float tube duplicating the emergent swim of the nymph. Whatever the approach chose a slow handtwist retrieve coupled with frequent pauses to imitate the flutter rest swimming motion of the nymph. By paying attention to the diving swallows and nighthawks observant anglers can find feeding fish with a minimum of effort.

On the premier Callibaetis waters of the south central interior hatching occurs from mid May through August. With each successive hatch the Callibaetis nymphs and duns decrease in size due to the reduced growth span between generations. The size 12 nymphs of the spring become size 14 or 16 by mid summer and tiny patterns work wonders into the fall as trout fatten up for the oncoming winter. Hatches occur on favorite waters with startling regularity, beginning the same time each season depending upon conditions. Cyclic in nature some years offers blanket hatches of epic proportions while other years see sporadic activity at best.