The May ICU is a CDC-collared Perdigon-style mayfly nymph with pearlescent flash cheeks that catch light as the fly tumbles through the drift. Norman Maktima’s Umpqua tutorial walks through the olive version on a size 14 jig hook with a silver slotted tungsten bead.
Construction starts with a UTC yellow olive thread base, with bead sizing scaled to hook: 3.2mm for a 14, down to 2.3mm for an 18. A sparse tail of speckled Coq de Leon is tied in and bound down along the shank to keep it sitting directly on top of the hook. The body is built with a slight taper of thread, then unspun and laid flat for a smooth finish. The ribbing is done by marking roughly an inch of the working thread with a Bic marker — not a Sharpie, which bleeds under UV resin — leaving one turn of unmarked thread to butt cleanly against the tail before ribbing forward in wide, well-defined segments. A coat of ultra-thin UV resin locks the body in.
For the cheeks, a length of medium flat pearl tinsel is folded around the bead and tied in on both sides, then left to hang while a ball of natural gray squirrel dubbing is built behind the bead to form the thorax. The thread is swapped to fluorescent sice UTC 70 for the head. A sparse CDC collar is set in a dubbing loop, trimmed for texture, and given one and a half turns to keep the profile thin and the sink rate fast. The tinsel loop is then drawn forward through the parted CDC on each side, splitting the collar and seating the pearl cheeks flush against the thorax before being tied off and trimmed.
The pattern is built for the emerger phase, when mayfly nymphs are transitioning to adults. It runs slim and fast-sinking, with the CDC breathing and the pearl cheeks pulsing flash as the fly rotates through the drift. It fishes well on a Euro rig, under a dry dropper, or swung through a hatch, and covers sizes 14 through 18. Umpqua also offers the pattern in a brown body with a copper bead.
Materials List
Hook: XC 400 sz 14
Bead: Slotted Tungsten bead Silver 3.2mm
Tying Thread: UTC 70D Yellow Olive
Tail: Coq De Leon
Rib: Black Bic permanent marker
Dubbing: Natural Spikey Squirrel Dub
Wing collar: CDC Natural Dun
Collar: UTC 70D Fl. Orange thread
